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Karnataka 1st PUC Biology Question Bank Chapter 19 Excretory Products and their Elimination

1st PUC Biology Excretory Products and their Elimination NCERT Text Book Questions and Answers

Question 1.
Define Glomerular Filtration Rate (GFR)
Answer:
Glomerular filtration rate refers to the quantity of filtrate formed by the kidneys per minute.
It is 125 ml per minute i.e., 180 liters per day.

Question 2.
Explain the autoregulatory mechanism of GFR.
Answer:
The kidneys have built-in mechanisms for the regulation of glomerular filtration rate. This regulation is carried out by the juxtaglomerular apparatus (JGA). JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact. A fall in GFR can activate the JG cells to release renin which can stimulate the glomerular blood flow and thereby the GFR back to normal.

Question 3.
Indicate whether the following statements are true or false:
(a) Micturition is carried out by a reflex.
(b) ADH helps in water elimination, making the urine hypotonic.
(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.
(d) Henle’s loop plays an important role In concentrating the urine.
(e) Glucose is actively reabsorbed in the proximal convoluted tubule.
Answer:
(a) True
(b) False
(c) True
(d) True
(e) True

Question 4.
Give a brief account of the countercurrent mechanism.
Answer:
Mammals have the ability to produce concentrated urine. The Henle’s loop and vasa recta play a significant role in this. The flow of filtrate in the two limbs of Henle’s loop is in opposite directions and thus forms a counter current. The flow of blood through the two limbs of the vasa recta is also in a counter-current pattern. The proximity between the Henle’s loop and vasa recta, as well as the counter-current in them, help in maintaining an increasing osmolarity towards the inner medullary interstitium i.e, from 300 mOsmolL^-1 in the cortex to about 1200 m OsmolL^-1 in the inner medulla. This gradient is mainly caused by NaCl and urea. NaCl is transported by the ascending limb of Henle’s loop which is exchanged with the descending limb of the vasa recta. NaCl is returned to the interstitium by the ascending portion of the vasa recta. Similarly, small amounts of urea enter the thin segment of ascending limb of Henle’s loop which is transported back to the interstitium by the collecting tubule.

The above-described transport of substances facilitated by the special arrange¬ment of Henle’s loop and vasa recta is called the countercurrent mechanism (Fig. 19.1). This mechanism helps to maintain a concentration gradient in the medullary interstitium. The presence of such interstitial gradient helps in an easy passage of water from the collecting tubule thereby concentrating the filtrate (urine). Human kidneys can produce urine nearly four times concentrated than the initial filtrate formed.

Diagrammatic representation of a nephron and vasa recta showing counter current mechanisms

Question 5.
Describe the role of the liver, lungs, and skin in excretion.
Answer:
Lungs is responsible for the elimination of large amount (18 liters/day) of CO2 and water vapour. The liver secretes bile, degraded steroid hormones, drugs, and certain vitamins.

The skin excretes certain substances through glands present in it e.g., glands which excrete sweat produce cooling effect and sebaceous glands eliminate wastes through sebnum.

Question 6.
Explain micturition.
Answer:
Micturition or urination is the process of expulsion of urine from the urinary bladder through the urethra.
This is accomplished by the simultaneous contraction of the smooth muscles of the urinary bladder wall and relaxation of the skeletal muscles of the sphincter around the opening of the bladder.
The expulsion of urine from the urinary bladder
Biology is called micturition. It is a reflex process, but in grown-up children and adults, it can be controlled voluntarily to some extent.

Question 7.
Match the items of Column I with those of column II:
Column I – Column II
(a) Ammonotelism- (i) Birds
(b) Bowman’s capsule – (ii) Water reabsorption
(c) Micturition – (iii) Bony fish
(d) Urlco’dlsm – (iv) Urinary bladder
(d) ADH – (v) Renal tubule
Answer:
(a) – (iii)
(b) – (v)
(c) – (iv)
(d) – (i)
(e) – (ii)

Question 8.
What is meant by the term osmoregulation?
Answer:
Osmoregulation. It is the maintenance of a fixed osmotic concentration inside the body cells and the extracellular fluids by controlling the amount of water and salts.

Question 9.
Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic, why?
Answer:
Terrestrial adaptation necessitated the production of lesser toxic nitrogenous wastes like urea and uric acid for the conservation of water. Mammals, many terrestrial amphibians, and marine fishes mainly excrete urea and are called ureotelic animals. Ammonia produced by metabolism is converted into urea in the liver of these animals and released into the blood which is filtered and excreted out by the kidneys. Some amount of urea may be retained in the kidney matrix of some of these animals to maintain the desired osmolarity.

Reptiles, birds, land snails, and insects excrete nitrogenous waste as uric acid in the form of a pellet or paste with a minimum loss of water and are called uricotelic animals. The process of excreting ammonia is Ammonotelism. Many bony fishes, aquatic amphibians, and aquatic insects are ammonotelic in nature. Ammonia, as it is readily soluble, is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions. Kidneys do not play any significant role in its removal.

Question 10.
What is the significance of the juxtaglomerular apparatus (JGA) in kidney function?
Answer:
The JGA plays a complex regulatory role. A fall in glomerular blood flow/glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in the blood to angiotensin I and further to angiotensin II.

Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release aldosterone.

Aldosterone causes reabsorption of Na+ and water from the distal parts of the tubule.

This also leads to an increase in blood pressure and GFR. This complex mechanism is generally known as the Renin-Angiotensin mechanism.

Question 11.
Name the following:

1. A chordate animal having flame cells as excretory structures
2. Cortical portions projecting between the medullary! pyramids in the human kidney
3. A loop of capillary running parallel to Henle’s loop.

Answer:

1. Cephalochordate (Amphioxus)
2. Columns of Bertini
3. Vasa Recta.

Question 12.
Fill in the gaps:

1. Ascending limb of Henle’s loop …………………. is to water whereas the descending limb is to it…………………..
2. Reabsorption of water from distal parts of the tubules is facilitated by hormone ………………….
3. Dialysis fluid contains all the constituents as in plasma except ………………….
4. A healthy adult human excretes (on an average) gm of urea/day…………………..

Answer:

1. Impermeable, permeable
2. ADH
3. Nitrogenous wastes
4. 25 – 30 gm.

1st PUC Biology Excretory Products and their Elimination Additional Questions and Answers

1st PUC Biology Excretory Products and their Elimination One Mark Questions

Question 1.
Define excretion.
Answer:
Excretion is the elimination of unwanted waste substances which have been produced as a result of metabolism within the cells of body.

Question 2.
What are ammonotelic animals?
Answer:
Animals that excrete ammonia are ammonotelic animals.

Question 3.
What are ureotelic animals?
Answer:
Animals excrete urea.

Question 4.
What are uricotelic animals?
Answer:
Animals excrete uric acid.

Question 5.
Which are the excretory organs in humans?
Answer:
Kidneys.

Question 6.
What are nephrons? (July 2007)
Answer:
Structural and functional units of kidneys.

Question 7.
What is the renal capsule?
Answer:
Connective tissue envelop around kidney is renal capsule.

Question 8.
Where do you find brush border in nephron?
Answer:
Proximal Convoluted Tubule (PCT).

Question 9.
What are glomeruli? (Oct. 2004)
Answer:
The network of blood capillaries inside Bowman’s capsule is called glomeruli.

Question 10.
Give an example of a Uricotelic animal. (April 83, March 89)
Answer:
‘Snake’ (Lizard, bird, Insect – anyone can be named)

Question 11.
What is Ureotelism? (April 85)
Answer:
The phenomenon of excretion of urea as the predominant nitrogenous waste material is called as Ureotelism.

Question 12.
Give an example of an ammonotelic animal. (Oct. 85, 92)
Answer:
Tadpoles of amphibia (Octopus, crustaceans, polychaete annelids – any one of these can be named)

Question 13.
What is the excretory unit In the kidney? (April 86)
Answer:
The Nephron is the excretory unit of the kidney.

Question 14.
Name the organ that is involved in Urea formation. (March 88, Oct. 93, 95)
Answer:
Urea is formed in the ‘Liver’.

Question 15.
Which hormones control the output of urine? (Mar. 89)
Answer:
The Anti diuretic hormone (ADH) or Vaso pressing

Question 16.
Name the internal lining of the Bowman’s capsule. (Oct. 86)
Answer:
The internal lining of the Bowman’s capsule is made up of simple squamous epithelium.

Question 17.
Where does ultrafiltration take place in the nephron?
Answer:
The Bowman’s Capsule.

Question 18.
What is dialysis? (Oct. 99, April 01, March 11)
Answer:
Dialysis is a process by which solutes in a solution are separated by diffusion through a semipermeable membrane.

Question 19.
What is primary urine? (Oct. 2002)
Answer:
Blood entering the glomerulus is filtered into the glomerular capsule, this filtrate which contains both essential and nonessential substances like water, glucose, vitamins, amino acids, nitrogenous wastes, ions, and plasma proteins is called primary urine.

Question 20.
What is the difference in the mode of transport between the thin and thick segments of the ascending limb of Henle’s loop?
Answer:
In the thin segment, transport of NaCl is passive while in the thick segment, it is active.

Question 21.
Glomerular filtrate has water, glucose, amino acids, and creatinine. Which of them are rapidly reabsorbed actively by blood? (Delhi 2003 C)
Answer:
Glucose and amino acids.

Question 22.
Longer the loop of Henle, the more hypertonic is the urine produced. Is this statement true or false? If false, rewrite correctly.
Answer:
It is true. (All India 2003 C)

Question 23.
In which part of nephron does filtration take place? (Delhi 2001 C)
Answer:
Bowman’s Capsule.

Question 24.
What Is the difference between the ascending and descending limbs of Henle’s loop with reference to permeability to water? (All India 2000)
Answer:

• Ascending limb is impermeable to water and permeable to solutes.
• Descending limb is permeable to water and impermeable to solutes.

Question 25.
What happens to the walls of the distal convoluted tubule (DOT) of a nephron, when vasopressin is released by the pituitary into the bloodstream? (Delhi 1999 C)
Answer:
DCT becomes permeable to water and reabsorb water from the filtrate and makes the urine hypertonic.

Question 26.
Name the excretory structures of
(1) Planaria
(2) Earthworm
Answer:

1. Flame cells
2. Nephridia

Question 27.
Name any two constituents of sweat, besides water. (Delhi 1998 C)
Answer:
Sodium chloride and lactic acid.

Question 28.
What are columns of Bertini in a kidney?
Answer:
The extensions of cortex in between the medullary pyramids as renal columns, are called columns of Bertini.

Question 29.
What is glomerulus?
Answer:
Glomerulus is a tuft of capillaries formed by the afferent arteriole in the hollow of Bowman’s capsule.

Question 30.
Name the parts of nephron that are present in the cortex of the kidney.
Answer:
Bowman’s capsule, Proximal Convoluted tubule and distal convoluted tubule.

Question 31.
What are peritubular capillaries ?
Answer:
The efferent arteriole emerging from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillaries.

Question 32.
What is vasa recta?
Answer:
The U- shaped peritubular capillary that runs parallel to the Henle’s loop is called vasa recta.

Question 33.
What is the driving force for glomerular filtration?
Answer:
Blood pressure in the glomerular capillaries is the driving force for glomerular filtration.

Question 34.
Name the layers that form the filtration membrane in the nephron.
Answer:
It is formed by three layers:

• Endothelium of glomerular capillaries
• Epithelium of Bowman’s capsule
• Basement membrane between the two.

Question 35.
What are podocytes?
Answer:
The epithelial cells of the Bowman’s capsule are called podocytes.

Question 36.
How are the filtration slits formed?
Answer:
The podocytes are arranged in an intricate manner so as to leave some minute spaces called filtration slits.

Question 37.
Why glomerular filtration called ultra filtration?
Answer:
Since the blood is filtered so finely through the membranes, that almost all the constituents of the plasma except the proteins are filtered, it is called ultra filtration.

Question 38.
Where is JGA located in the kidney?
Answer:
JGA is located where the distal convoluted tubule is in contact with the afferent arteriole in cortex.

Question 39.
Expand JGA.
Answer:
Juxta Glomerular Apparatus.

Question 40.
What is JGA?
Answer:
JGA is a special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at the location of their contact.

Question 41.
Name the type of cells that form the Inner lining of PCT.
Answer:
Brush bordered cuboidal epithelium.

Question 42.
Why does filtrate become concentrated as it passes through the descending limb of Henle’s loop?
Answer:
Descending limb is permeable to water but not to solutes, so the filtrate becomes concentrated.

Question 43.
Name two parts in the nephron, when tubular secretion of H⁺ and K⁺ ions takes place.
Answer:
Proximal Convoluted Tubule and Collecting Duct.

Question 44.
Name the site of nephron from where urea comes out.
Answer:
Collecting Duct.

Question 45.
Name the compounds that maintain the concentration gradient in the medullary interstitium.
Answer:
Sodium Chloride, urea.

Question 46.
What causes the release of ANF ?
Answer:
An increase in the blood pressure / blood volume in the atria, causes the release of ANF.

Question 47.
Name the mechanism that acts as a check for the Renin angiotensin mechanism.
Answer:
Atrial Natriuretic Factor (ANF) mechanism.

Question 48.
What is micturition?
Answer:
The process of release of urine is called micturition.

Question 49.
Name two accessory excretory organs in man.
Answer:
Lungs, liver and skin.

Question 50.
What is uremia?
Answer:
Uremia is a condition in which urea is accumulated in blood due to malfunctioning of kidneys.

Question 51.
What is the term for inflammation of glomerules in nephron ?
Answer:
Glomerulonephritis.

1st PUC Biology Excretory Products and their Elimination Two Marks Questions

Question 1.
Explain amonotelism with an example. (Oct. 83)
Answer:
Amonotelism is a phenomenon wherein the nitrogenous waste material is predominantly excreted in the form of Ammonia Example: Tadpole of Frog.

Question 2.
Write short notes on Urlcotelism. (April 87, Oct. 90)
Answer:
Uricoteiism is a phenomenon in which the nitrogenous waste material is predominantly excreted in the form of uric acid. The animals which excrete this nitrogenous waste material predominately are called as the uricotelic animals.

Uricotelism is a adaptation to conserve water in animals which face acute scarcity of water and have to maintain a normal level of water inside then body.Examples: Insects, Reptiles and birds excrete Uric acid. These animals use minimal amount of water or absolutely no water for excretion of uric acid. Specially water is used only for flushing.

Question 3.
Write a note on ultra-filtrationl (Oct. 87)
Answer:
‘Ultra filtration’ is the first step in the formation of urine. It is the process wherein substances from the blood brought into the glomerulus are filtered into the Bowman’s capsule of the nephron, through the ultra fine endothelia-capsular barrier or membrane. It is made possible by the high blood pressure in the glomarular capillaries and the osmotic pressure exerted by the contents on either side (glomerular lumen + Bowman capsular lumen) of the endothelia capsular membrane. The glomerular filtrate or primary urine resembles the blood plasma in its chemical composition, except for the high molecular weight (large molecules) organic molecules.

Question 4.
What la excretion? Name the types of nitrogenous wastes. (April 97,2002)
Answer:

• Excretion is a process in which toxic wastematerials produced during biochemical reactions (metabolic activity) in the cells are eliminated from the body.
• One of the Excretory product which is toxic to the body and has to be eliminated, is the nitrogenous waste material formed from either the nitrogenous compounds got by deamination of amino acids or breakdown of nucleic acids.

They are three types of nitrogenous waste materials formed pre-dominantly in animals, they are

• Ammonia
• Urea
• Uric acid.

Question 5.
Write a note on the glomerulus. (April 98)
Answer:
The glomerulus is a tuft a capillaries found inside the Bowman’s capsule of the nephron. It is formed by the renal artery which branches into arteriole which in turn supply each and every Bowman’s capsule forming the capillary mass, the glomerulus. Blood is brought for purification into the glomerulus by the afferent arteriole and leave it through the efferent arteriole. The glomerular membrane forms an intricate connection with membrane of the Bowman’s capsule forming the endothelia capsular membrane for filtration.

Question 6.
Write four functions of Kidneys. (April 2000, Oct. 2000)
Answer:
The main functions of Kidneys are:

• Maintaining levels of urea and excretory materials in the blood. Kidneys also remove toxins.
• Maintaining acid-base balance of body by controlled excretion of H⁺ ions.
• Maintaining levels of various salts and ions.
• Maintaining optimum amounts of water in the blood and body.

Question 7.
Write a note on renal calculi. (Oct. 2002, M.Q.P.)
Answer:
Renal calculi or Kidney stones are usually composed of calcium oxalate, calcium phosphate, Magnesium phosphate or uric acid. Calcium oxalate stones are the most common. They develop within the kidney or its collecting system. High blood calcium levels, alkaline urine, bacterial infection and diet are some of the reasons for this condition.

Question 8.
What are the two modes of tubular reabsorption from nephrons ? Name the substances absorbed by each of these modes. (All India 2000)
Answer:
Two modes of reabsorption are:

1. Active absorption: It involves expenditure of energy.
   Eg: glucose, amino acids, Na⁺ etc. are absorbed actively.
2. Passive absorption: It does not involve any energy expenditure and follows concentration gradient. Eg: nitrogenous waste, water, Cl^– are absorbed passively.

Question 9.
Describe the blood vessels called vasa recta. What is their function ? (Delhi 2000 C)
Answer:
Vasa Recta are ‘U’ shaped, thin walled capillaries that arise from efferent arteriole and run parallel to the Henle’s loop.

They retain the reabsorbed ions in the medullary tissue fluid and maintain its high osmolarity and are involved in the counter current mechanism.

Question 10.
Mention two advantages of uricotelism In birds. (All India 1999C)
Answer:
Birds excrete uric acid and are called uricotelic.
Advantages:

• Uric acid requires very little or no water for its elimination.
• Uric acid is far less toxic and can be eliminated slowly.

Question 11.
What are the functions of nephridia? Name an animal having photonephridia.
Answer:

• Nephridia help to eliminate nitrogenous waste.
• They maintain the fluid and ionic balance in the body.
  Phtonephridia are present in planaria, rotifers etc.

Question 12.
Name two types of excretory organs found among arthropods, with an example for each.
Answer:

• Insects like cockroach, grasshopper etc. have Malpighian tubules as excretory structures.
• Crustaceans like prawn, crab etc. have antennal (green) glands as excretory structures.

Question 13.
What is the importance of tubular secretion? Name two substances that are secreted into the filtrate.
Answer:
‘Tubular secretion is an important step in urine formation as it helps in the maintenance of ionic and acid base balance of body fluids. The tubular cells secrete substances like H⁺, K⁺ and ammonia into the filtrate.

Question 14.
Mention the role of DCT in urine formation.
Answer:

• Conditional reabsorption of Na⁺ and water takes place in this segment.
• It is also reabsorbed HCO₃
• There is selective secretion of hydrogen and potassium ions to maintain the pH and sodium-potassium balance in the blood.

Question 15.
What is the role of ADH in kidney functioning ?
Answer:

• ADH renders the wall of distal convoluted tubule (DCT), collecting tubule and collecting duct permeable to water and facilitates reabsorption of water from the filtrate, thereby preventing diuresis.
• It also affects the kidney function by its constrictory effect on the blood vessels, this causes increase in the blood pressure and glomerular blood flow.

Question 16.
What Is meant by Glycosuria and Ketonuria?
Answer:

• Presence of glucose in the urine is termed as Glycosuria.
• Presence of Ketone bodies in the urine is termed as Ketonuria.
• Both these conditions indicates the presence of diabetes mellitus.

Question 17
What is the ultimate method of correcting acute renal failure? Describe.
Answer:
Kidney transplantation is the ultimate method in the correction of acute renal failures. A functioning kidney is used in transplantation from a donor, preferably a close relative, to minimise its chances of rejection by the immune system of the host.

1st PUC Biology Excretory Products and their Elimination Three Marks Questions

Question 1.
Draw a sketch showing human urinary system and label the parts.
Answer:

Question 2.
Draw a neat labelled diagram of longitudinal section of Kidney.
Answer:

Question 3.
Give a diagrammatic representation of a nephron showing blood vessels, duct and tubule.
Answer:

Question 4.
Describe glomerular filtration In human nephrons. (Delhi 2003)
Answer:
Glomerular filtration is the first step in urine formation, which is the filtration of blood carried out by the glomerulus. The glomerular capillary blood pressure causes filtration of blood through 3 layers, i.e., the endothelium of glomerular blood vessels, the epithelium of Bowman’s capsule and a basement membrane between these two layers.

The epithelial cells of Bowman’s capsule called podocytes are arranged in an intricate manner so as to leave some minute spaces called filtration slits. Blood is filtered finely through these membranes, that almost all the constituents of the plasma except the proteins pass onto the lumen of the Bowman’s capsule. Therefore, it is considered as a process of ultra filtration. On an average 1100 – 1200 ml of blood is filtered by the kidneys per minute. The glomerular filtration rate Is about 125 ml /minute.

Question 5.
What is the full form of ADH? How does ADH control osmoregulation in human kidney? (Foreign 2001)
Answer:
ADH – Antidiuretic Hormone. ADH is secreted when there is excessive loss of fluid from the body. ADH facilitates water reabsorption from distal convoluted tubule, collecting tubule and collecting duct, thereby preventing diuresis. ADH can also affect the kidney function by its constrictory effects on blood vessels. This causes an increase in blood pressure, which increases the glomerular blood flow and thereby the GFR.

Question 6.
Describe the general structure of renai corpuscle. What happens when blood flows through it?
Answer:
The Bowman’s capsule along with the glomerulus is known as Malpighian corpuscle or Renal corpuscle. Bowman’s capsule is a double-walled cup-like structure. The wall is made of epithelial tissue. The hollow of the cup is occupied by the glomerulus.

Blood flowing through the glomerulus is filtered, which is the first step in urine formation and is called ultrafiltration.

The filtration membrane is made up of

• The endothelium of glomerular capillaries.
• The epithelium of Bowman’s capsule
• The basement membrane between the two.

Question 7.
Describe the process of hemodialysis.
Answer:
Urea can be removed by the process called hemodialysis in patients suffering from uremia. Blood drained from a convenient artery is pumped into a dialysing unit after adding an anti coagulant like heparin. The unit contains a coiled cellophane tube surrounded by a fluid having the same composition as that of plasma except the nitrogenous waste.

The porous ceilophare membrane of the tube allows the passage of molecules based on concentration gradient. As nitrogenous wastes are absent in the dialysing fluid, these substances freely move out, thereby clearing the blood. The cleared blood is pumped back to the body through a vein after adding anti heparin to it.

Question 8.
Give an account of disorders of excretory system.
Answer:

• Uremia: It is a condition which leads to the accumulation of urea in the blood due to the malfunctioning of kidneys, which is highly harmful and may lead to kidney failure.
• Renal calculi: Stone or insoluble mass of crystallised salts like oxalates etc. formed within the kidney is termed as Renal calculi.
• Glomerulonephritis: It is a condition of inflammation of glomeruli of kidney.

1st PUC Biology Excretory Products and their Elimination Five Marks Questions

Question 1.
Classify animats based on the nature of excretory products, giving examples. (April 84)
Answer:
The animals are classified into 3 types depending on the type of nitrogenous waste material excreted by them. They are:

1. Ammonotelic animals
2. Ureotelic animals
3. Uricotelic animals.

(1) Ammonoteiic animals: are the animals which predominantly excrete their nitrogenous waste material in the form of ammonia. Examples: Crustaceans, Polychaete annelids, Octopus, Sepia, tadpoles of Amphibians and some teleosts fishes (bony fishes)

(2) Ureotelic animals; are the animals which predominantly excrete their nitrogenous waste material in the form of Urea. Examples: Eiasmobranchs, Amphibians and Mammals.

(3) Uricotelic animals: are the animals which predominantly excrete their nitrogenous waste material in the form of uric acid Examples: Reptiles and Birds.

Question 2.
Explain the process of urine formation. (Oct. 84, 91,93, 2000, 2004, April 86, 89, 93, 1995, 99, 2006, 2009, July 2008, 2010)
Answer:
During urine formation, the nitrogenous waste materials are removed as urine from the blood without losing the valuable molecules of blood in the process. It involves three main stages namely.

1. Ultra filtration (Glomerular filtration)
2. Reabsorption (tubular)
3. Tubular secretion.

1. Ultra filtration: Involves the removal or filtration of substances from blood of the glomerular lumen into the Bowman’s capsular lumen through the Ultra fine endothelia capsular membrane. Glomerular filtration is caused due to changes in blood pressure, the pressure of the Bowman’s capsular fluid and osmotic pressures excreted by contents in glomerular and Bowman’s lumen. The glomerular filtrate resembles the blood plasma in its chemical composition except for the molecules of high molecular weight.

2. Tubular reabsorption: This is the second step or stage in urine formation and involves the reabsorption of physiologically important substances into the surrounding capillaries when the primary urine moves down route in the nephron tubules. The reabsorption may be passive cr active at various regions of the convoluted tubule. During this process glucose, amino acids, inorganic salts and some water is absorbed. Some of the absorptions are under the influence of hormones.

3. Tubular secretion: (Active secretion) This is the last stage or step in the urine formation at the end of which a hypertonic or highly concentrated urine is formed for excretion. During this stage, the capillaries surrounding the convoluted tubule actively secrete certain unwanted substances which could not be the filtered in the Bowman’s capsule by the glomerulus into the filtrate of the tubular lumen.

As a result of these 3 processes or stages .in urine formation, homeostasis is blood is restored and waste products remain in the tubular fluid forming concentrated urine for excretion from urine. Two hormones come into play during the process namely ADH – for reabsorption of water when the body has the deficit of water and Aldosterone helping in reabsorption of ions like K+ when the body faces the deficit of these ions.

Question 3.
With a neat diagram explain the structure of nephron. (Apr. 85, 01,2005, June 2009, March 2010)
Answer:

Nephrons are the fundamental units of the kidney. Each nephron is made up of
(a) A Bowman’s capsule
(b) A convoluted tubule

(a) The Bowman’s capsule is cup shaped and double walled enclosing a capsular space. It is lined by the simple squamous epithelium. Its cup shaped depression holds the highly folded tuft of blood capillaries called the glomerulus. The glomerulus brings blood for purification in terms of nitrogenous waste material, removal of excess of ions, salts, water etc.

It is formed by the branch of afferent renal artery namely the renal arteriole. After filtration into the Bowman’s capsule the remaining constituents are drained by the efferent arteriole which again branch and rebranch around the convoluted tubule of the nephron to form the particular capillaries and the peritubular capillaries join to

‘form renal venules which in turn form the renal vein carrying away blood from kidney with reabsorbed materials and reset homeostasis back into the circulation. The glomerular epithelium & Bowman’s capsular epithelium form an intricate association called endothelia capsular barrier.

(b) The convoluted tubule: starts from the hind endo. the cup-shaped Bowman’s capsule. It is thin, elongated, tubular, double-walled enclosing a tubular space. It is lined by cuboidal epithelium. The convoluted tubule is composed of 3 parts, each having a distinct function. They are:

(1) Proximal convoluted tubule: It is wide tube starting from Bowman’ capsule and is involved in absorption of ions, amino acid glucose etc. by active reabsorption and water by passive reabsorption forming the primary urine or filtrate. The epithelium (endothelium) is brush bordered in this region.

(2) Henle’s loop: The proximal convoluted tubules narrows down and dips into a thin ‘U’ shaped tubule (of various length in difference animals) called the Henle’s loop. It helps in reabsorption of water, Na⁺, Cl^– etc. from the filtrate by Active transport.

(3) The Distal convoluted tubule: The Henle’s loop broadens and leads into the distal convoluted tubule. Here active reabsorption & secretion of unwanted wastes takes place. The reabsorption of water and ions is under the influence of Hormones (ADH and Aldosterone). The lining of Distal convoluted tubule is made up of cuboidal epithelium.

The entire convoluted tubule is surrounded by the peritubular capillaries formed by efferent arteriole arising from glomerulus. Required substances are reabsorbed from the tubules into these peritubular capillaries and unwanted substances are secreted from the peritubular capillaries into the distal convoluted tubule.

The Distal convoluted tubules of many nephrons join the collecting tubules and the nephron fluid formed at the final region of the convoluted tubule i.e. the DCT is drained into the collecting tubules from various nephrons.

Question 4.
Explain the role of different regions of a nephron in urine formation.
Answer:
(i) Glomerulus: The first step of urine formation, ultrafiltration, occurs from the glomerular capillaries into the lumen of the Bowman’s capsule.

(ii) Proximal convoluted tubule (PCT): In this segment, nearly 70 – 80% of water and electrolytes are reabsorbed. PCT helps in maintaining the pH and ionic balance of the body fluids, by selective secretion of H⁺, ammonia and K⁺ into the filtrate and by absorbing bicarbonate ions.

(iii) Henle’s loop: This segment plays an important role in maintaining high osmolarity of the medullary interstitial fluid. The descending limb is permeable to water and impermeable to solutes. So filtrate becomes hypertonic. The ascending limb is, impermeable to water but permeable to solutes, so filtrate becomes hypotonic.

(iv) Distal Convoluted tubule (DCT): Reabsorption of Na⁺ and water takes place in this segment. DCT also reabsorbs HCO₃ ions and secretes NH³⁺, hydrogen and potassium ions into the filtrate.

(v) Collecting duct: Large amounts of water is reabsorbed from this region. This segment also allows the transport of small amounts of urea, into the filtrate.

(v) Collecting duct: Large amounts of water is reabsorbed from this region. This segment also allows the transport of small amounts of urea, into the medullary interstitium. It also plays a role in maintaining the pH and ionic balance of the body fluids.

You can Download Chapter 12 Organic Chemistry Some Basic Principles and Techniques Questions and Answers, Notes, 1st PUC Chemistry Question Bank with Answers Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 1st PUC Chemistry Question Bank Chapter 12 Organic Chemistry: Some Basic Principles and Techniques

1st PUC Chemistry Organic Chemistry: Some Basic Principles and Techniques One Mark Questions and Answers

Question 1.
Which compound is formed when an organic nitrogen compound is fused with sodium metal?
Answer:
NaCN

Question 2.
Name two elements which are detected by Lassaigne’s test.
Answer:
Nitrogen, Chlorine, Bromine, Iodine and Sulphur.

Question 3.
Name the blood red coloured compound formed in Lassaigne’s test conducted on an organic compound containing both nitrogen and sulphur.
Answer:
Ferric Thiocynate [Fe(CNS)₃]

Question 4.
Name the compound used to absorb water in the estimation of hydrogen in an organic compound by Liebig’s method.
Answer:
Anhydrous calcium chloride.

Question 5.
Name the compound formed when an organic compound containing. nitrogen is heated with concentration sulphuric acid and potassium
sulphate.
Answer:
Ammonium Sulphate.

Question 6.
During estimation of nitrogen by Kieldahl’s method, copper sulphate is added to sulphuric acid. Why?
Answer:
Copper sulphate acts as catalyst.

Question 7.
Which method is employed for the estimation of carbon and hydrogen organic compounds?
Answer:
Liebig’s method.

Question 8.
Which type of organic compounds cannot be Kjeldahlised?
Answer:
Nitro compounds (R-NO₂) and azo (-N = N-) compounds.

Question 9.
Name the type of isomerism shown by the following compounds CH₃COOH and HCOOCH₃.
Answer:
Functional isomerism.

Question 10.
What is the difference in the molecular formulae of any two successive members in a homologous series?
Answer:
-CH2 –

Question 11.
Is Isobutene a straight chain or branched chain hydrocarbon?
Answer:
Branched chain hydrocarbon.

Question 12.
Ring compounds containing more than one type of atoms in the ring are
called
Answer:
Heterocyclic compounds.

Question 13.
The molecular formulae of four hydrocarbons belonging to a homologous series are CH₄, C₂H₆, C₅H₈ and C₄H₁₀. Write the general formula of this
series.
Answer:
C_nH_2n+2

Question 14.
Why do organic compounds of a given homologous series show similar properties?
Answer:
They possess the same functional group.

Question 15.
What is the acronym for International Union of Pure and Applied Chemistry?
Answer:
IUPAC

Question 16.
Write resonance hybrid structure of benzene.
Answer:

Question 17.
Define resonance (mesomeric) effect.
Answer:
The permanent polarity is produced by the interation of lone pair & π electrons in conjugate a system of an organic molecule.

Question 18.
Indicate the type of electron pair involved in M effect.
Answer:
π-electron pair or lone pair electrons.

Question 19.
What is +R effect ?
Answer:
Shift of electron pair away from substituent in congjuagte system.

Question 20.
Define inductive effect.
Answer:
The permanent polarity in an saturated organic molecule due to small displacement of sigma bond pair of electrons towards more electronegative atom.

Question 21.
Which electron displacement effect involves displacement of s-electrons?
Answer:
Sigma bond pair of electrons.

Question 22.
What is +1 effect ?
Answer:
Small displacement of sigma bond pair of electrons away from substituent.

Question 23.
Give an example of a group which exerts +1 effect.
Answer:
Alkyl group (methyl group)

Question 24.
Out of (CH₃)₂ CH – and CH₃ – group, which is a better electron releasing group?
Answer:
(CH₃)₂CH-

Question 25.
What is -1 effect ?
Answer:
Small displacement of sigma bond pair of electrons towards substituent.

Question 26.
Give an example of electron withdrawing group.
Answer:
Nitro group (-NO₂)

Question 27.
Identify the stronger electron withdrawing substituent from each of the following pairs.

1. -NO₂ and -Cl
2. -C ≡ N and -Br
3. -Cl and -OCH₃
4. -C₆H₅ and -F

Answer:

1. -N0₂
2. -C ≡ N
3. -Cl
4. -F

Question 28.
What is R-effect?
Answer:
Shift of electron pair towards the substituent in a conjugate system.

Question 29.
What is Inductive effect?
Answer:
The polarisation of one σ bond caused by polarization of adjacent a bond due to difference in electro-negativity.

Question 30.
Sketch the resonance structure of Benzene.
Answer:

Question 31.
What is the suitable adsorbent in the process of column chromography?
Answer:
Al₃O₃ (alumina)

Question 32.
Which process is used to purify impure sample or camphor, contaminated with sand?
Answer:
Sublimation

Question 33.
Which gas is liberated in Kjeldahl’s method?
Answer:
Ammonia gas (NH₃)

Question 34.
What is Lassaigne’s extract ?
Answer:
When organic compound is fused with sodium metal and then extracted by water, it is called Lassaigne’s extract.

Question 35.
Which gas is liberated in Dumas method?
Answer:
N₂

Question 36.
Define Crystallization.
Answer:
The process of getting crystals when hot saturated solution of a compound is cooled is called crystallization.

Question 37.
What is basic principle of chromotography ?
Answer:

• Paper,
• Fhinlayer,
• Column

Question 38.
What is steam distillation ?
Answer:
The distillation which is carried out with the help of steam is called steam distillation.

Question 39.
Suggest the method to purify:
(a) Camphor containing salt impurity
(b) Kerosene Oil containing water
(c) Mixture of Benzene and Toulene
(d) Sugar and Naphtalene
Answer:
(a) sublimation
(b) by solvent extraction
(c) fractional Distillation
(d) treat with water and filter

Question 40.
Why is fusion of an organic compound with sodium required ?
Answer:
It is done so as to convert organic compound into inorganic compound.

Question 41.
Name two classes of compounds in which Kjeldahl’s method cannot be used for estimation of nitrogen.
Answer:
Nitro compounds, Azo compounds and compounds containing nitrogen in ring, e.g., pyridine.

Question 42.
Which class of compounds are tested with the help of Beilstein test.
Answer:
Halogen containing organic compounds but some other compounds like urea is respond to this test.

Question 43.
What are formulae of

• Sodium nitroprusside
• Ferric ferrocyanide ?

Answer:

• Na₂[Fe(CN)₅NO]
• Fe₂[Fe(CN)₆]₃

Question 44.
Which elements are estimated by Liebig’s Method?
Answer:
Carbon and Hydrogen

Question 45.
What is the relationship between molecular mass and equivalent mass of an acid?
Answer:

Question 46.
What is relationship between molecular formula and empirical formula of a substance ?
Answer:

Question 47.
Which effect involves the displacement of electron pair under the infulence of an attacking reagent ?
Answer:
Electromeric effect.

Question 48.
What is an electromeric effect ?
Answer:
The shift of π electron pair of a multiple bond to one of the bonded atoms during the attack of electrophile or nucleophile.

Question 49.
Which type of E effect Operates during the attack of proton on ethane molecule ?
Answer:
+E effect.

1st PUC Chemistry Organic Chemistry: Some Basic Principles and Techniques Two Marks Questions and Answers

Question 1.
What is Electrophile ? Give example.
Answer:
The electron deficient molecules or positively charged ions which are capable of accepting on electron from substrate molecule are called electrophiles.
Positive electrophiles : H⁺, Cl⁺, Br⁺, NO₂, N⁺ = O, R⁺ (carbocations) etc.
Neutral electrophiles : SO₃, BF₃, AICl₃, Cl

Question 2.
What are Nucleophiles ?
Answer:
The molecules or negatively charged ions which are capable of donating an electron pair to electron deficient centre of the substrate are called nucleophiles.
Negative nucleophiles:

Question 3.
What is the difference between organic and inorganic compounds ?
Answer:

Property	Organic Compounds	Inorganic Compounds
Chemical nature	Compounds of carbon	Compounds of elements other than carbon
Bonding	Covalent	Ionic
Melting . and boiling points	Low, generally Volatile	High, generally non-­volatile
Solubility	Soluble in organic solvents, insoluble in water.	Soluble in water, insoluble in organic solvents.
Electrical conduction	Non – conductors ; solutions and liquids – non – electrolytes	Conductors ; solutions and liquids – conductors

Question 4.
What is the difference between Electrophilic Reagents and Nucleophilic Reagents.
Answer:

Electrophilic Reagents	Nucleophilic Reagents
1. These are electron loving species.	1. These are nucleus loving species
2. These are electron deficient species.	2. These are electron rich species.
3. They attack the site of high electron density in the substrate.	3. They attack the site of low electron density in the substarte.
4. They may be +vely charged ions (cations) or neutral molecules.	4. They may be negatively charged ions (anions) or neutral molecules.
5. They possess an atom with incomplete octet.	5. They possess an atom withlone pair of electrons.
6. They are Lewis acids.	6. They are Lewis bases.
7. They accept an electron pair from the substrate to form a covalent bond.	7. They done an electron pair to the substrate to form a covalent bond.

Question 5.
What is Homolytic fission (Homolysis) ? Give reason.
Answer:
Definition: The fission of a covalent bond, in which each of the two species produced, retains one electron of shared electron pair, is called hemolytic fission or homolysis,
Eg: \(\mathrm{Cl}-\mathrm{Cl} \stackrel{\text { Homolysis }}{\longrightarrow} 2 \mathrm{Cl}^{-}\) (Chloroine free radicals)

Question 6.
What is Heterolytic Fission (Heterolysis)?
Answer:
The fission of a covalent bond, in which ionic species are produced due to unequal disrtribution of bonded electron pair, is called heterolytic fission or heterolysis.

Question 7.
What is Homolytic Fission and Heterolytic Fission?
Answer:

Homolytic Reagent	Heterolytic Fission
1. In this case, the covalent bond breaks symmetrically.	1. In this case, the covalent bond breaks unsymmetrically.
2. Each species, obtained, retains one electron from shared electron pair.	2. The more electronegative otom retains the shred electron pair.
3. Electrically neutral free radicals are formed which carry an old certain.	3. Electrically charged ions (cations and anions) are formed.
4. It takes place in the presence of sunlight, U.V. light or by pyrolysis.	4. It takes place in the presence of polar solvent.

Question 8.
What are Free Radical ? Give example.
Answer:
A free radical can be defined as an atom or group of atoms having an odd or impaired electron. Putting a dot (•) against the symbol of atom or group of atoms.
Example :
(Chlorine free radicals)

Question 9.
What are the characteristics of Free Radicals.
Answer:
Characteristics of Free Radicals

• Free radicals are generally electrically neutral.
• They carry on odd (unpaired) electron.
• They are highly unstable.
• They are short-lived.
• They are highly reactive species due to the presence of odd electrons.
• They have a tendency to pair up with the odd electrons to form a covalent bond.
• They are generally formed either in presence of U.V. or visible light or in the presence of peroxides.

Question 10.
What is Alicylic compounds? Give Example.
Answer:
These are saturated hydrocarbons joined by covalent bond to form ring structure.

Question 11.
What are Aromatic Compounds ? Give example.
Answer:
These are the compounds containing atleast one benzene ring.

Question 12.
What are Heterocyclic compound? Give example.
Answer:
These are the compounds containing ring structure in which one or more carbon atoms are replaced by hetero atoms such as N, S, O etc.,

Question 13.
What is functional group? Give example.
Answer:
A functional group is defined as “an atom or group of atoms present in a molecule which determines most of the chemical properties of the particular class of organic compounds”.
Example : CH₃ – OH methyl alcohol.

Question 14.
What are carbanions ? Give example.
Answer:
A reaction intermediate formed by heterolysic fission of a covalent bond which contains one negatively charged carbon with eight electrons in its valence shell is called carbanion.
The heterolytic cleavage of a covalent bond as indicated in the following reactions gives carbanions.
Example : \(\mathrm{CH}_{3}-\mathrm{MgI} \longrightarrow \mathrm{CH}_{3}^{-}+\mathrm{M}^{+} \mathrm{gI}\)

Question 15.
What are carbocations ? Give Example.
Answer:
A reaction intermediate formed by heterolytic fission of a covalent bond which contains one positively charged carbon with three bond pair electrons (sextext of electrons) is called carbocation.
The heterolytic fission of bromomethane yields methyl carbocation and bromide ion as shown below.
Example :

Question 16.
What is the difference between Carbocation & Carbanion.
Answer:

Carbocation	Carbanion
1. The central carbon atom is +vely charged.	1. The central carbon atom is -vely charged.
2. It is an electron deficient species.	2. It is an electron rich species.
3. The central carbon atom possesses six electrons in its outermost shell.	3. The central carbon atom possesses eight electrons in its outermost shell.
4. The central carbon atom is in sp2 state of hybridisation.	4. The central carbon atom is in sp3 state of hybridisation and carries a lone pair of electrons.
5. Its shape is triangular planner.	5. Its shape is pyramidal.
6. It can accept an electron pair from a nucleophile to form a covalent bond.	6. It can donate an electron pair to an electrophile to form a covalent bond.

Question 17.
What is positive inductive effect (+1 effect) ? Give example.
Answer:
In this effect the substituent (Y) releases electron pair away from itself. In other words a bond pair of electrons are displaced away from the substituent.
Eg : All alkyl groups.

Question 18.
What is negative inductive effect (-1 effect) ? Give example.
Answer:
In this effect, the sigma bond pair of electrons are displaced towards electron withdrawing substituent (X).
The order of electron withdrawing ability (intensity of -1 effect) of a few substituent is given below.

Question 19.
What is electromeric effect ? Give example.
Answer:
It is the complete transfer of shared pair of electrons of a multiple bond to one of the atom in the presence of attacking reagent.
Eg.: H+, -CN^–, etc.,

Question 20.
What is +E effect ? Give example.
Answer:
When the transfer of electrons takes place towards the attacking reagent, the effect is called +E effect.
For example, the addition of an acid to alkenes.

Question 21.
What is -E Effect ? Give example.
Answer:
When the transfer of electron takes place way from the attacking reagent, the effect is called -E effect.
For example, the addition of cyanide ion (CN-) to carbonyl group (>C = 0)

Question 22.
What is mesomeric effect ? Give example.
Answer:
The polarity developed in a molecule, as a result of interaction between two π-bond or a π-bond and a lone pair of electrons is referred to as mesomeric effect.
Groups with +M or +R effect.
—Cl, —Br, —I, -NH₂, -NHR, -NR₂, -OH, -OR, -SH, -OCH₃ etc.,
Groups with -M or -R effect.
-NO₂, -C ≡ N, -C-, -CHO, -COOH, -COOR etc.,

Question 23.
What is the difference between Inductive effect & Mesomeric effect?
Answer:

Inductive Effect	Mesomeric Effect
1. It operates in saturated compounds.	1. It operates in unsaturated compounds especially having conjugated systems.
2. It involves electrons of a – bonds.	2. It involves electrons of π – bonds or lone pair of electrons.
3. The electron pair is slightly displace from its position and hence partial charges are developed.	3. The electron pair is completely transferred and hence unit positive and negative charges are developed.
4. It is transmitted over a short distance it becomes negligible after second carbon atom in the chain.	4. It is transmitted through the entire chain provided conjugation is present.

Question 24.
What is the difference between Inductive Effect and Electromeric Effect.
Answer:

Inductive Effect	Electromeric Effect
1. It is permanent in nature.	1. It is temporary in nature.
2. It is due to electronegative atom present in the molecule itself.	2. It is due to approach of the attacking reagent.
3. It is the mobility of electrons along C-C single bond.	3. It is the mobility of electrons in a multiple bond (double or triple bond).

Question 25.
What is resonance energy ? Mention the resonance energy of Benzene.
Answer:
The phonomenon in which two or more structures can be written for a compound but none of them represents it correctly is called resonance. The actual structure of the compound is said to be a resonance hybrid. 36 kcal mol^-1 is the resonance energy of benzene.

Question 26.
Explain hyperconjucgation effect.
Answer:
The electron release of alkyl group bonded to unsaturated system in which delocalization of electrons takes place through overlap between C – H sigma (σ) orbital and pi (π) bond orbited or vacant p-orbital is known as hyperconjugation.

Question 27.
What is substitution reaction ? Give example.
Answer:
The reaction in which an atom of group atoms attached to carbon atom in a substrate molecule, is replaced another atom is called substitution reaction.
Ex: \(\mathrm{CH}_{4}+\mathrm{Cl}_{2} \stackrel{\mathrm{UV}}{\longrightarrow} \mathrm{CH}_{2} \mathrm{Cl}+\mathrm{HCl}\)

Question 28.
What is addition reaction ? Give example.
Answer:
The reaction in which the attacking reagent adds up to the substrate molecule without elimination of any molecule are called addition reaction.
Ex :
\(\mathrm{CH} \equiv \mathrm{CH}+\mathrm{H}_{2} \frac{\mathrm{Ni}}{14: \mathrm{C}} \cdot \mathrm{CH}_{2}=\mathrm{CH}_{2}\)

Question 29.
What is the test for sulphur ?
Answer:
To a small amount of sodium extract, freshly prepared solution of sodium nitro prusside is added, a deep violet colour indicates the presence of sulphur.
Ex:

1st PUC Chemistry Organic Chemistry: Some Basic Principles and Techniques Three/Four Marks Questions and Answers

Question 1.
How is the detection of carbon and hydrogen by copper oxide test ?
Answer:
Organic compounds undergo oxidation in the presence of a suitable oxidizing agent. In this process, carbon is oxidized to CO₂ and hydrogen is oxidized to water.

Procedure : The compound is initially lime water mixed with dry cupric oxide. The mixture is strongly heated in a hard glass test, tube fitted with a cork and a delivery tube. The liberated gases are passed into lime water. Carbon present in compound is oxidised by cupic oxide to carbon
dioxide, which turns lime water milky. The hydrogen present in the compound is converted into water which turns anhydrous copper sulphate to blue hydrated salt.

Question 2.
How is the prepartion on of Lassaigne’s is filtrate ?
Answer:
Procedure : A piece of dry sodium is introduced into a fusion tube and heated till it melts. A drop of few crystals of the organic compound is added to the fusion tube. The mixture is fused gently on a Bunsen flame initially. The tube is then heated until red hot and plunged into in a mortar containing distilled water. The contents are ground throughly and filtered. The filtrate is known as sodium fusin extract, stock solution or Lassaigne’s extract. The filtrate is divided into three parts, which are used for the detection of nitrogen, sulphur and halogen in organic compound.

Question 3.
How is detection of nitrogen by Lassaigne’s filtrate ?
Answer:
A few crystal of ferrous sulphate are added to the first part of the filtrate. The mixture is boiled and cooled. It is acidified with hydrochloric acid and a few drops of ferric chloride solution are added. Sodium cyanide in the filtrte reacts with ferrous sulphate to give sodium ferrocyanide. It further reacts with ferric chloride to give a blue coloured solution of ferric ferrocyanide.

Question 4.
How is the detection of sulphur by Lassaigne’s is filtrate ?
Answer:
Lead acetate test: second part of the filtrate is treated with excess of acetic acid and lead acetate solution. A black precipitate of lead sulphide is formed.

Question 5.
Explain the test for detection of halogens by Lassaigne’s is filtrate
Answer:
Silver nitrate test : A portion of the stock solution is boiled with dil. HN03, cooled and silver nitrate is added. A white precipitate soluble in ammonium hydroxide shows the presence of chlorine. A pale yellow precipitate slightly in ammonium hydroxide shows the presence of bromine. A yellow precipitate insoluble in ammonium hydroxide ” shows the presence of iodine.

Question 6.
Explain the test for detection of phs phosphorus in an organic compound.
Answer:
Organic compound containing phosphorous is fused with sodium peroxide. The
phosphorus of the compound is oxidised to phosphate. The fused mass is extracted with water and filtered. The filtrate containing sodium phosphate is boiled with nitric acid and then treated with ammonium molybdate. A yellow solution of precipitate indicates the presence of phosphorus.

Question 7.
Explain the estimation of phosphorus in organic compound by carius method.
Answer:
It is also estimated by carius method the known mass of organic compound containing phosphorus is heated with fuming HNO₃ when phosphorus is oxidised to phosphoric acid (H₃PO₄). To this, magnesia mixture (MgSO₄ + NH₄OH + NH₃CI) is added when phosphoric acid precipitates as magnesium ammonium phosphate (MgNH₄PO₄). This precipitate is filtered, washed, dried and ignited when it is converted to magnesium pyrophosphate (Mg₂P₂O₃).
\(2 \mathrm{MgNH}_{4} \mathrm{PO}_{4} \stackrel{\Delta}{\longrightarrow} \mathrm{Mg}_{2} \mathrm{P}_{2} \mathrm{O}_{7}+2 \mathrm{NH}_{3}+\mathrm{H}_{2} \mathrm{O}\)
The weight of Mg₂P₂CO₇ is determied from which the percentage of phosphorus is the compound can be calculated.
Observations and Calculations:

1. Mass of organic compound taken = w₁, g.
2. Mass of Mg₂P₂O₇ obtained = W₂g.

We have \(\underset{222 \mathrm{g}}{\mathrm{Mg}_{2} \mathrm{P}_{2} \mathrm{O}_{7}} \equiv \underset{62 \mathrm{g}}{2 \mathrm{P}} \text { Now, } 222 \mathrm{g} \mathrm{Mg}_{2} \mathrm{P}_{2} \mathrm{O}_{7}\)contains 62g of phosphorus.
W₂g of Mg₂p₂O₇ Will contain \(\frac{62 \times w_{2}}{222} g\) of phosphorus
This amount of phosphorus was present in wig of the compound
\(\therefore \% \mathrm{P}=\frac{62 \times \mathrm{w}_{2}}{222} \times \frac{100}{\mathrm{w}_{1}}\)

Question 8.
0.189g of an organic substance containing chlorine gave carius method
0. 287g of silver chloride. Calculate the percentage of chlorine in the substance.
Answer:

1. Mass of organic compound taken (W1) = 0.189 g
2. Mass of AgCli ppt (W2) = 0.287 g

Now , %\(\mathrm{Cl} 2=\frac{35.5 \times \mathrm{w}_{2}}{143.5} \times \frac{100}{\mathrm{w}_{1}}=\frac{35.5 \times 0.287 \times 100}{143.5 \times 0.189}=37.57\)

Question 9.
0.2632g of silver bromide is obtained from 0.2562g of an organic compound. Find the percentage of bromine in the compound.
Answer:

1. Mass of organic compound (W1) = 0.2562g
2. Mass of AgBr obtained (W2) = 0.2632g.

\(\text { Now } \% \mathrm{Br}_{2}=\frac{80 \times \mathrm{w}_{2}}{188} \times \frac{100}{\mathrm{w}_{1}}=\frac{80 \times 0.2632 \times 100}{188 \times 0.2562}=43.71\)

Question 10.
In Leibig’s method. 0.24 g of organic compound on combustion with dry oxygen produced of 0.62 g of CO2 and 0.11 g of II2O. Determine the percentage composition of the compound.
Answer:
Mass of organic compound = m = 0.24 g .
Mass of carbon dioxide formed = 0.62 g
Mass of water formed = 0.11 g
Percentage of carbon = \(\frac{12}{4} \times \frac{0.62}{0.24} \times 100=70.45\)
Percentage of hydrogen = \(\frac{2}{4} \times \frac{0.11}{0.24} \times 100=5.09\)
Percentage of oxygen = [100 – (70.5 + 5.0)] = 24.46

Question 11.
In Carius method of estimation of halogen, 0.20 g of organic compound gave 0.15 g of silver bromide. Calculate the percentage of bromine in the compound.
Answer:
Mass of organic compound (m1) = 0.20 g
Mass of silver bromide formed (m2) = 0.15 g
188 (108 + 80) g of AgBr contains 80 g of bromine
∴ 0.20 g of AgBr contains = \(\frac{80 \times 0.15}{188} \mathrm{g}=0.0638 \mathrm{g} \text { of } \mathrm{Br}\)
Percentage of bromine = \(\frac{80 \times 15 \times 100}{188 \times 20}=31.92\)
The percentage of bromine in the given compound = 31.92

1st PUC Chemistry Organic Chemistry: Some Basic Principles and Techniques Five Marks Questions and Answers

Question 1.
Describe with a neat diagram the estimation of carbon and hydrogen by Leibig’s method.
Answer:
Principle : A known mass of an organic compound is strongly heated with dry cupric oxide (CuO), when carbon and hydrogen are quantitatively oxidized to CO₂ and H₂O respectively. The masses of CO₂ and H₂O thus formed are determined. From this, the percentages of carbon and hydrogen can be calculated.
Procedure : Pure and dry oxygen is passed through the entire assembly of the apparatus (Fig) till the CO₂ and moisture is completely removed.

A boat containing weighed organic substances is introduced inside from one end of the combustion tube by opening it for a while. The tube is now strongly heated till the whole of the organic compound is burnt up. The flow of oxygen is continued to drive CO₂ and water vapours completely to the U-tubes. The apparatus is cooled and the U-tubes are weighed separately.
Observed and Calculations.

1. Mass of organic compound taken = w.g.
2. Mass of water produced = x g (Increase in mass of CaCk tube)
3. Mass of carbon dioxide produced = y g. (Increase in mass of KOH tube)

To determine % of carbon
Molar mass of CO₂ = 44g mol^-1
Now, 44g of CO₂ = contains 12 g of C.
∴ y g of CO₂ will contain of \(\frac { 12y }{ 44 }\) g of C.
This amount of carbon was present in w. g. of the substance
\(\therefore \% \mathrm{C}=\frac{12 \mathrm{y}}{44} \times \frac{100}{\mathrm{w}}\)
To determine % of Hydrogen
Molar mass of water = 18 g mol^-1
Now 18g of H₂O contains 2 g of H₂
∴ x g of H₂O will contain \(\frac { 2x }{ 18 }\) g of H₂
This amount of hydrogen was present in weight of substance.
\(\therefore \% \mathrm{H}_{2}=\frac{2 \mathrm{x}}{18} \times \frac{100}{\mathrm{w}}\)

Question 2.
How is the estimation of Nitrogen in ogranic compound by Dumas method.
Answer:
Principle : The organic compound containing nitrogen when heated with excess of copper oxide in the atmosphere of carbon dioxide, yields nitrogen in addition to carbon dioxide and water.

Traces of nitrogen oxides formed during combustion of organic compound are reduced to nitrogen by passing the gaseous mixture over a heated copper gauze. The percentage of nitrogen present in a given organic compound is calculated from the volume of nitrogen collected over potassium hydroxide solution from a known mass of organic compound.

Procedure : The apparatus used for the estimation of nitrogen by this method is shown in the figure.

A known mass of organic compound is mixed with copper oxide and placed in the combustion tube. The carbon dioxide gas is passed through the combustion tube to displace air present in the tube. The combustion tube is now heated in the furnace, the nitrogen evolved collects in the nitrometer. The volume of the nitrogen collected is recorded after adjusting the levels of potassium hydroxide solution in the two limbs are equal. Room temperature and atmosphere pressure are recorded.
Calculation:
Mass of organic compound = mg
Volume of nitrogen in nitrometer = V cm³
Room temperature = t° C = (273 + t) K
Atmosphere pressure = P1 mm
Aqueous tension at room temperature = P’ mm
Pressure of dry nitrogen gas formed = P = (P – P’) mm
Volume of nitrogen at STP (V0) = \(\frac{\mathrm{PV} \times 273}{760 \times(273+\mathrm{t})} \mathrm{cm}^{3}\)
22,400 cm³ of nitrogen of STP = 28 g of nitrogen
Mass of V0 cm³ of nitrogen = \(\frac{28 \times V}{22,400} g\)
Percentage of nitrogen = \(\frac{28 \times V_{0} \times 100}{22,400 \times m}\)

Question 3.
Describe an experiment to determine the percentage of nitrogen in an organic compound by Kjeldahl’s method.
Answer:
Principle : When a nitrogenous organic compound is heated with cone. H₂SO₄ using (CUSO₄K₂SO₄) as a catalyst, the nitrogen from the compound is quantitatively converted to ammonium sulphate.

This ammonium sulphate is decomposed by heating with excess of alkali and the ammonia evolved is absorbed in known excess of a standard solution of H₂SO₄. Part of acid is neutralized by ammonia. The excess of acid left behind after neutralization with ammonia is estimated by back titration with standard alkali. From this, the amount of acid actually consumed by ammonia can be obtained which can be used to determine the percentage of nitrogen in the compound.

Procedure : A known exact mass of organic compound (about 0.5g) ix mixed with lOg K₂SO₄, Ig CuSO₄ and 25 ml of cone. H₂SO₄. The mixture is heated strongly in a Kjeldahl’s flask. Till the contents become clear. This step is known as digestion.

The Kjeldahl’s flask is now cooled and the liquid is heated in a round-bottomed flask with excess of caustic soda solution The ammonia evolved is absorbed in a known volume of a standard acid.
The amount of unreacted acid is determined by titrating it against a standard alkali.
(NH₄ )2S0₄ + 2NaOH → 2NH₃ ↑+ Na₂S0₄ + 2H₂0
Observation :

1. Mass of organic compound taken = Weight
2. Normality of standard acid = N
3. Volume of standard acid taken = V1 ml
4. Volume of alkali (Normality = N) required for back titration = V2 ml

Calculation: Volume of acid used up by ammonia = Volume of ammonia produced
= (V2 – V1) = V ml of normality N.
Now,
1000 ml of 1 normal NH₃ = 17g NH₃ = 14g N₂
∴ Vml of N- normal ammonia will contain \(\frac{14 \times \mathrm{N} \times \mathrm{V}}{1000} \mathrm{gN}_{2}\)
This amount of nitrogen was present in w g of the compound
\(\therefore \% \mathrm{N}_{2}=\frac{14 \times \mathrm{N} \times \mathrm{V}}{1000} \times \frac{100}{\mathrm{w}} \text { or } \% \mathrm{N}_{2}=\frac{1.4 \mathrm{NV}}{\mathrm{w}}\)
Where, N and V are the normality and volume respectively of the acid used up by ammonia.

Question 4.
How is the estimation of halogens by Carius method ?
Answer:
When an organic compound containing halogen (Cl, Br or 1) is heated in a sealed tube with fuming nitric acid and excess of silver chloride, silver halide is formed from the mass of silver halide obtained, the percentage of the halogen can be calculated.
Procedure : In a hard glass tube (Carius tube), 5ml of fuming HNO₃ and 2 to 2.5 g AgNO₃ are taken. A small narrow weighing tube, containing a small amount (nearly 0.15-0.2g) of accurately weighed organic compound, is introduced in the Carius tube in – such a way that nitric acid does not enter the weighing tube. The Carius tube is now sealed and heated in a furnace at 300°C for about six hours.

The tube is then cooled and its narrow end is cut off and the contents are completely transferred to a beaker by washing with water. The precipitate of silver halide formed is filtered through a weighed sintered glass crucible. It is washed, dried and weighed. Observation and calculation :

1. Mass of organic compound taken = W1g
2. Mass of silver halide obtained = W2 g

(a) For chlorine :
\(\underset{143.5 \mathrm{g}}{\mathrm{AgCl}} \equiv \underset{35.5 \mathrm{g}}{\mathrm{Cl}}\)
143.5g of AgCl contains 35.5 g of chlorine
w2g of Agcl Will contain \(\frac{35.5 \times w_{2}}{143.5} g\) of chlorine
This amount of chlorine was present in wig of the compound.
\(\therefore \quad \% \mathrm{Cl}_{2}=\frac{35.5 \times \mathrm{w}_{2}}{143.5} \times \frac{100}{\mathrm{w}_{1}}\)

(b) For bromine :
\(\underset{188 \mathrm{g}}{\mathrm{AgBr}} \equiv \underset{80 \mathrm{g}}{\mathrm{Br}}\)
188g of AgBr contains 80g of bromine
W2 g of AgBr will contain \(\frac{980 \times w_{2}}{188} g\) of bromine.
\(\therefore \% \mathrm{Br}_{2}=\frac{80 \times \mathrm{w}_{2}}{188} \times \frac{100}{\mathrm{w}_{1}}\)

(c) For Iodine :
\(\underset{235 \mathrm{g}}{\mathrm{Agl}} \equiv \underset{127 \mathrm{g}}{\mathrm{I}}\)
235g of Agl contains 127g of iodine
W2 g of Agl will contain \(\frac{127 \times w_{2}}{235} g\) of iodine
\(\therefore \quad \% \mathrm{I}_{2}=\frac{127 \times \mathrm{w}_{2}}{235} \times \frac{100}{\mathrm{w}_{1}}\)

You can Download Chapter 22 Chemical Coordination and Integration Questions and Answers, 1st PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 1st PUC Biology Question Bank Chapter 22 Chemical Coordination and Integration

1st PUC Biology Chemical Coordination and Integration NCERT Text Book Questions and Answers

Question 1.
Define the following
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone
Answer:
(a) Exocrine glands: These glands have ducts. The secretions of these glands are carried by ducts to a particular organ to regulate some metabolic activities.
(b) Endocrine glands: They lack ducts and their secretions (hormones) released directly into the blood for transport to the target tissues.
(c) Hormones: Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.

Question 2.
Diagrammatically Indicate the location of the various endocrine a lands In our body.
Answer:

Question 3.
List the hormones secreted by the following:
(a) Hypothalamus
(b) Pituitary
(c) Thyroid
(d) Parathyroid
(e) Adrenal
(f) Pictures
(g) Testis
(h) Ovary
(I) Thymus
(j) Atrium
(k) Kidney
(l) G-i Tract
Answer:
(a) Hypothalamus:

• Growth hormone-releasing hormone
• Growth hormone inhibiting hormone (Somatostatin)
• Gonadotrophin releasing hormone (GnRH)

(b) Pituitary:

• Growth hormone
• Prolactin
• Thyroid-stimulating hormone
• Adrenocorticotrophic hormone
• Luteinizing hormone
• Follicle-stimulating hormone
• Melanocyte stimulating hormone
• Oxytocin
• Vasopressin

(c) Thyroid:

• Tetraiodo thyronine or thyroxine
• Triiodothyronine
• Thyrocalcitonin (TCT)

(d) Parathyroid:

• Parathyroid hormone (PTH)

(e) Adrenal:

• Adrenaline/epinephrine
• Noradrenaline/Norepinephrine
• Corticoids
• Cortisol
• Aldosterone

(f) Pancreas:

• Glucagon
• Insulin

(g) Testis:

• Testosterone

(h) Ovary:

• Estrogen
• Progesterone (I) Thymus:
• Thymosin 0 Atrium:
• Atrial Natriuretic Factor (ANF)

(k) Kidney:

• Erythropoietin

(I) G.l. tract:

• Gastrin
• Secretin
• Cholecystokinin (CCK)
• Gastric inhibitory peptide (GP)

Question 4.

Fill in the blanks:

Hormones Target gland
(a) Hypothalamic hormones ………..
(b) Thyrotrophln (TSH) ………..
(c) Corticotrophln (ACTH) ………..
(d) Gonadotrophins (LH, FSH) ………..
(e) Meianotrophin (MSH) ………..
Answer:
(a) Pituitary
(b) Thyroid
(c) Adrenal Cortex
(d) Testis and Ovaries
(e) Pineal gland

Question 5.
Write short notes on the functions Of the following hormones:
(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(c) Thymosins
(d) Androgens
(e) Estrogens
(f) Insulin and Glucagon
Answer:
(a) Parathyroid hormone (PTH)
• When the level of calcium ions in the plasma decreases, PTH is secreted.
• It increases the level of Ca²⁺ ions in the blood/plasma by
(i) bone reabsorption (demineralization/ dissolution of bones).
(ii) stimulating reabsorption of Ca²⁺ ions by the renal tubules.
(iii) stimulating the absorption of Ca²⁺ from the alimentary canal.
(iv) since it increases the level of Ca²⁺ ions in the blood, it is called hypercalcemic hormone..
• Along with TCT, PTH plays an important role in the calcium balance of the body.

(b) Thyroid hormones: Two types of thyroid hormones –
(i) Tetraiodothyronine(TT₄)
(ii) Triiodothyronine (TT₃)
Thyroid hormones perform the following functions:
(i) They regulate the basal metabolic rate.
(ii) They control the metabolism of
carbohydrates, fats, and protein.
(iii) They influence the maintenance of water and electrolyte balance.
(iv) They support the process of red blood cell formation.

(c) Thymosin: Thymosin is secreted by the thymus and plays a major role in the differentiation of T-lymphocytes, which provided cell-mediated immunity.
Thymosins also promote the production of antibodies to provide humoral immunity.

(d) Androgens: Androgens are secreted
from the Leydig cells of the testis.
Functions:
(i) Androgens regulate the development, maturation and functioning of the male secondary sex organs.
(ii) They stimulate spermatogenesis.
(iii) They act on the CNS and the influence on male sexual behaviour.
(iv) They produce anabolic effects on proteins and carbohydrate metabolism.

(e) Estrogens: Ovarian hormone.
Functions: Stimulates the growth and
the functioning of female sex organs.
• It stimulates the development of female sex characteristics.
• It regulates female sexual behaviour.

(f) Insulin and Glucagon: Secreted by the pancreas.
• Insulin is a peptide hormone which plays a major role in the regulation of glucose homeostasis. Insulin mainly acts on hepatocytes and adipocytes (cells of adipose tissue) and enhancing cellular glucose uptake and utilisation.
• Glucagon is also a peptide hormone and plays an important role in maintaining normal blood glucose levels.
• Glucagon acts mainly on the liver cells (hepatocytes) and stimulates glycogenolysis resulting in increased blood sugar (hyperglycemia).
• This hormone also stimulates the
process of gluconeogenesis which also contributes to hyperglycemia.
• Glucagon reduces cellular glucose uptake and utilisation. Thus glucagon is a hyperglycemic hormone.

Question 6.
Give example(s) of:
(a) Hyperglycemic hormone and hypoglycemic hormone
(b) Hypercalcemlc hormone
(c) Gonadotrophic hormones
(d) Progestational hormone
(e) Blood pressure lowering hormone
(f) Androgens and estrogens
Answer:
(a) Hyperglycemic hormone: Glucagon. Hypoglycemic hormone: Insulin.
(b) Hypercalcemic hormone: Parathyroid hormone.
(c) Gonadotrophic hormone: Follicle-stimulating hormone(FSH) or luteinizing hormone (LH).
(d Progestational hormone: Progesterone.
(e) Blood pressure lowering hormone: Atrial Natriuretic Factor (ANF)
(f) Androgen : Testosterone. Estrogen : Estrogens, estrone, estradiole.

Question 7.
Which hormonal deficiency is responsible for the following:
(a) Diabetes mellitus
(b) Goitre
(c) Cretinism
Answer:
(a) Insulin
(b) Thyroxine
(c) Thyroxine

Question 8.
Briefly mention the mechanism of action of FSH.
Answer:
Mechanism of FSH:

• FSH is a protein hormone.
• It binds to membrane-bound receptors and stimulates the production of the second messenger, cyclic AMP or Ca”1-1″.
• The second messenger brings about biochemical responses, which results in the production of physiological response, e.g.- the growth of the ovarian follicles and secretion of estrogens from the follicle cells.

Question 9.
Match the following:
Column I – Column II

(a) T4 – (i) Hypothalamus
(b) PTh – (ii) Thyroid
(c) GnRH – (iii) Pituitary
(d) LH – (iv) Parathyrold
Answer:
(a) – (ii)
(b) – (iv)
(c) – (i)
(d) – (iii)

1st PUC Biology Chemical Coordination and Integration  Additional Questions and Answers

1st PUC Biology Chemical Coordination and Integration One Mark Questions

Question 1.
Mention the hormone produced by pars intermedia of the Pituitary. (April 86)
Answer:
The Melanocyte – stimulating hormone (or M.S.H.)

Question 2.
Where are pituicytes found? (Oct. 90)
Answer:
The ‘Neurohypophysis’.

Question 3.
Which secretes LTH? (April 92)
Answer:
The Adenohypophysis.

Question 4.
Which Endocrine gland produces ACTH? (April 93)
Answer:
The pituitary gland.

Question 5.
Which hormone is called as pregnancy hormone? (April 99, July 2007)
Answer:
Progesterone.

Question 6.
Mention any one function of oxytocin. (Oct. 99)
Answer:
Contraction of smooth muscles of the uterus during parturition.

Question 7.
Name the hormone secreted by Corpus luteum. (April 2000)
Answer:
Progesterone

Question 8.
Expand TSH. (Oct. 2004)
Answer:
Thyroid Stimulating Hormone.

Question 9.
Which disorder is caused due to hypersecretion of somatotropin in children? (Apr. 2007)
Answer:
Gigantism.

Question 10.
Name the gametokinetic factor. (July 2008)
Answer:
FSH.

Question 11.
Give reason (March 2009)
FSH is a gametokinetic factor.
Answer:
FSH stimulates the production of gametes, hence called gametokinetic factor.

Question 12.
What are endocrine glands?
Answer:
Glands which do not have ducts and pour their secretions (hormones) directly into the blood for transport to target tissues are called endocrine glands.

Question 13.
What are the two types of hormones produced by the hypothalamus?
Answer:
Releasing hormones and inhibiting hormones.

Question 14.
Name the bony cavity in which the pituitary gland is present.
Answer:
Sella turcica.

Question 15.
Name the two divisions (regions) of the pituitary gland.
Answer:
Adenohypophysis and neurohypophysis.

Question 16.
Name the two portions of the adenohypophysis.
Answer:
Pars distalis and pars inter media

Question 17.
What is the other name of neurohypophysis?
Answer:
Pars nervosa.

Question 18.
Which hormone regulates the growth of the mammary glands and the formation of milk in them?
Answer:
Prolactin (PRL)

Question 19.
Expand ACTH.
Answer:
Adrenocorticotrophic hormone.

Question 20.
What are glucocorticoids?
Answer:
‘Glucocorticoids are steroid hormones synthesized and secreted by the adrenal cortex which is stimulated by ACTH.

Question 21.
What stimulates the growth and development of the ovarian follicles in females?
Answer:
Follicle-stimulating hormone (FSH)

Question 22.
Why vasopressin is called the Anti-diuretic hormone?
Answer:
Vasopressin acts on the kidney and stimulates reabsorption of water and reduces the loss of water through urine. Hence it is called Anti-diuretic hormone.

Question 23.
Name the hormone of the pineal gland.
Answer:
Melatonin.

Question 24.
What is the thyroid gland composed of?
Answer:
The thyroid gland is composed of follicles and stromal tissues.

Question 25.
Why is oxytocin called birth hormone? (Delhi 2002 C, Delhi 1999)
Answer:
Oxytocin stimulates a vigorous contraction of the uterus and facilitates childbirth.

Question 26.
If for any reason the release of ADH Is Inhibited, how will this affect the volume of urine produced?
Answer:
The volume of urine decreases.

Question 27.
Name the neurohormone which Inhibits the secretion of growth hormone from the anterior pituitary.
Answer:
Somatostatin.

Question 28.
What is a goiter?
Answer:
Deficiency of iodine results in enlargement of the thyroid gland, a condition known as goiter.

Question 29.
Name the protein hormone secreted by the thyroid gland.
Answer:
Thyrocalcitonin (TCT)

Question 30.
What stimulates the secretion of parathormone?
Answer:
Low calcium ion level in the blood.

Question 31.
Where Is the thymus gland located?
Answer:
The thymus gland is located on the dorsal side of the heart and aorta.

Question 32.
What makes Immunity weak in old Individuals?
Answer:
Thyrnus is degenerated in old individuals resulting in decreased production of thymosins, which makes immune responses of old persons weak.

Question 33.
Name the two types of tissues in adrenal gland.
Answer:
Adrenal medulla and adrenal cortex.

Question 34.
What are catecholamines?
Answer:
Hormones of the adrenal gland, adrenaline and noradrenaline are collectively called as catecholamines.

Question 35.
What happens to the glycogen concentration in the liver cells, when the concentration of adrenaline in the bloodstream increases?
Answer:
Glycogen concentration decreases.

Question 36.
What are corticoids?
Answer:
The hormones secreted by adrenal cortex are called as corticoids.

Question 37.
Name the main glucocorticoid In our body.
Answer:
Cortisol.

Question 38.
Name one mineralocortlcold. (Delhi 2002 C, Foreign 1999)
Answer:
Aldosterone.

Question 39.
Name the hormone secreted by B – cells of islet of Langerhans.
Answer:
Insulin.

Question 40.
Name the cells that produce androgens.
Answer:
Ley dig cells.

Question 41.
What is glycogenesis ?
Answer:
The process of conversion of glucose to glycogen in the liver is called glycogenesis.

Question 42.
Expand CCK
Answer:
Cholecystokinin

1st PUC Biology Chemical Coordination and Integration Two Marks Questions

Question 1.
Distinguish between endocrine and exocrine glands. (April 93)
Answer:
Endocrine glands are specialised invaginations of the surface epithelium which elaborate and secrete chemical substances called hormones into the blood to be carried to the target organ. These are ductless glands and their secretions are produced in minute quantities. Any increase or decrease of hormones leads to clinical conditions (disease or abnormalities).
Eg: Pituitary gland.

Exocrine glands are also produced by surface epithelium. These elaborate and secrete chemical substances called enzymes and transport them to the area of action through ducts (ducted glands)

Eg: Gastric glands: The amount of secretion of enzymes depends on the quantity of substrate they have to act upon.

Question 2.
Name the two hormones secreted the posterior lobe of the pituitary, giving one functions of calls. (Oct. 97)
Answer:

• Oxytocin (OT) – Its Chief function is in the contraction of smooth muscles during child birth or parturitions.
• Vasopressin: (or ADH – Antidiuretic hormone) – Its chief function is to maintain and control water balance in the body and to maintain kidney functions.

Question 3.
What are the functions of Vasopressin ? (April 2002)
Answer:
Functions of Vasopressin or ADH

(a) It controls the water balance of the body by increasing the reabsorption of water in kidney tubules and producing a hypertonic urine.

(b) It also causes the contraction of the smooth muscle fibres of blood vessels thereby raising blood pressure. Under secretion of ADH [Antidiuretic Hormone] causes diabetes insipidus.

Question 4.
Mention any two functions of oxytocin. (March 2008)
Answer:

• Contraction of smooth muscles during childbirth.
• Helps in lactation.

Question 5.
Explain how the hypothalamus controls pituitary gland.
Answer:
Hormones originating in the hypothalamic neurons, pass through axons and are released from their nerve endings. These hormones reach the pituitary gland through a portal circulatory system and regulate the functions of the anterior pituitary. The posterior pituitary is under the direct neural regulation of the hypothalamus.

Question 6.
Name the two partitions of the pituitary gland and two hormones secreted by each.
Answer:
Two portions of pituitary gland are:

• Adeno hypophysis:
  Hormones secreted are Prolactin (PRL) Thyroid stimulating hormone (TSH) etc.
• Neurohypophysis:
  Hormones secreted are oxytocin and vasopressin.

Question 7.
What are the functions of oxytocin ?
Answer:

• Oxytocin acts on the smooth muscles of our body and stimulates their contraction.
• In females, it stimulates a vigorous contraction of uterus at the time of child birth, and milk ejection from the mammary gland.

Question 8.
Name the gland that functions as a biological clock in our body. Where is this gland located ? Name Its one secretion.
Answer:
Pineal gland functions as a biological clock in our body. It is located on the dorsal side of forebrain. Pineal secretes a hormone called melatonin.

Question 9.
Name the two hormones secreted from the follicles of thyroid. Mention one symptom of hypothyroidism and name the disorder. (All India 2003)
Answer:
Two hormones secreted are

• Thyroxine
• Tri iodothyronine.

Hypothyroidism in children results in stunted growth, mental retardation, low intelligence quotient and abnormal skin. The disorder is known as cretinism.

Question 10.
What are the functions of thyroid hormones?
Answer:

• Thyroid hormones play an important role in regulation of the basal metabolic rate.
• They support the process of RBC formation
• They control metabolism of carbohydrates, fats and proteins.
• Maintenance of water and electrolyte balance.

Question 11.
A person is suffering from calcium deficiency in spite of taking a calcium rich diet. Explain how this condition may have occurred ? (Delhi 2005 C)
Answer:
It may be due to the hyposecretion of parathyroid hormone. Damage in parathyroid gland may have lead to this condition. PTH plays an important role in absorption of calcium from the digested food and reabsorption of calcium by the renal tubules. Hence, hyposecretion of PTH results in calcium deficiency in spite of taking calcium rich diet.

Question 12.
Where is thymus gland located in the human body ? (All India 2005 C)
Answer:
Thymus gland is located on the dorsal side of the heart and aorta. Thymus gland secretes hormone thymosins which play a major role in the development of the immune system.Thymosins play a major role in the differentiation of T- lymphocytes, which provide cell-mediated immunity and also promote production of antibodies to provide humoral immunity.

Question 13.
Name the two hormones secreted by adrenal medulla and their function.
Answer:
The two hormones secreted by adrenal medulla are

• Adrenaline {Epinephrine)
• Noradrenaline (norepinephrine)

Functions:

• They are secreted in response to stress and any emergency situation. ,
• These hormones increase alertness, pupillary dilation, piloerection, sweating etc.
• They stimulate breakdown of glycogen, lipids and proteins.

Question 14.
What is diabetes mellitus ? How is it treated?
Answer:
Prolonged hyper glycemia leads to the disorder diabetes mellitus which is associated with loss of glucose through urine and formation of harmful compounds known as ketone bodies. Diabetes patients are treated with insulin therapy.

Question 15.
Name the hormones produced by Ley dig cells. Give any two functions of it.
Answer:
Ley dig cells produces hormones called androgens mainly testosterone.
Functions:

• Androgens regulate the development, maturation and functions of male accessory sex organs.
• They play a major stimulatory role in the process of spermatogenesis.

Question 16.
Name two steroid hormones from ovary with one function of each.
Answer:

• Estrogen: They regulate female sexual behaviours and stimulate the growth and activities of female secondary sex organs.
• Progesterone: They support pregnancy and acts on mammary gland and help in milk secretion.

Question 17.
Name four major peptide hormones.
Answer:

• Gastrin
• Secretin
• Cholecystokinin
• Gastric inhibitory peptide.

1st PUC Biology Chemical Coordination and Integration Three Marks Questions

Question 1.
Name three hormones produced by adenohypophysis with function for each.
Answer:

• Prolactin (PRL): Regulates the growth of mammary gland and formation of milk in them
• Thyroid stimulating hormone (TSH): It stimulates the synthesis of secretion of thyraid hormones from the thyroid gland.
• Follicle stimulating hormone (FSH): It regulates growth and development of the ovarian follicles in females.

Question 2.
Name the three layers of adrenal cortex. Name two hormones secreted by adrenal cortex.
Answer:
The three layers are:-

• Zona reticularis (inner layer)
• Zona fasciculata (middle layer)
  Zona glomerulosa (outer layer). The adrenal cortex secretes many hormones called as corticoids. The two main hormones are cortisol and aldosterone.

Question 3.
Name the divisions of hormones on basis of their chemical nature with one example for each.
Answer:
Hormones can be divided into four groups on basis of their chemical nature.

• Peptide, polypeptide, protein hormones Eg: insulin, glucagon
• Steroids Eg: cortisol, testosterone
• Lodothyronines Eg: thyroid hormones
• Amino – acid derivatives Eg: epinephrine

Question 4.
Briefly explain the mechanism of hormone action.
Answer:
Hormones produce their effects on target tissues by binding to specific proteins called hormone receptors located in the target tissues only. Hormone receptors present on the cell membrane of the target cells are called membrane boird receptors and the receptors present inside the target cell are called intracellular receptors, mostly nuclear receptors. Binding of a hormone to its receptor leads to the formation of a hormone-receptor complex. Each receptor is specific to one hormone. Hormone Receptor complex formation leads to certain biochemical changes in the target tissue. Target tissue metabolism and hence physiological functions are regulated by hormones.

1st PUC Biology Chemical Coordination and Integration Five Marks Questions

Question 1.
Name the pituitary hormones and state one function each.
(April 83, 98, 99, 2006, March 2011)
OR
List any five hormones of the adenohy-pophysis (anterior lobe) and mention one function each of them. (July 2008,2009)
Answer:
The pituitary gland produces a totally 9 hormones; 6 of them from the anterior lobe, 1 from the intermediate lobe and 2 from the posterior lobe. The list with one function each is given below.

(1) Growth hormone (GH) or Somototrophin: The basic function of this hormone is to stimulate body weight and rate of growth of the body in terms of muscle, bone structure, cartilage etc.

(2) Thyroid stimulating hormone (STH): regulates the growth of the thyroid gland and increase in thyroid activity.

(3) Adrenocortlcotrophic hormone (ACTH): Regulates the hormonal secretions of the Adrenal cortex (Steroid hormones) and Increase Adrenocortical activity.

(4) Gonadotrophic hormones: Stimulating the growth and activity of gonads

• Follicle stimulating hormone (FSH): stimulates ovarian follicular growth in female (Ovary) and stimulates the increased production of sperms in male (Testis – semiferous tubules)
• Luteinizing hormones (LH): Stimulates final maturation of graafian follicle in the ovary. Along with FSH it also stimulates production of progesterone in females. ICSH- in males, it stimulates the testis to produce androgens.

(5) Prolactin (PRL): Stimulates growth of mammary glands and production of milk in females.

(6) Melanocyte – stimulating hormone: Stimulates the increased production of Melanin pigment and its dispersal in mammalian skin.

(7) Vasopressin (or Antidiuretic hormone – ADH): Acts on kidney tubules and controls the water (metabplism) balance, i.e. increases reabsorption of water in kidney tubules (distal part) whenever the body faces a deficit in water.

Question 2.
What is neurohypophysis? Mention the hormones secreted by it with their target organs and functions? (April-85, Oct. 92)
Answer:
The neurohypophysis forms the posterior lobe of the pituitary. It is also called pars nervosa. It is made up of nervous tissue and terminations of neurosecretory fibres of neuro-secretory cells located in the perotic and paraventricular nuclei of the hypothalamus. It acts as a storage area for the hormones secreted by the neurosecretory cells. These hormones are also called neurohormones.

Neurohypophysis releases 2 types of hormones.

(1) Oxytocin (OT) – Its target organs are the uterus and mammary glands. In the uterus it helps in the contraction of smooth muscles during parturation or child birth. In the mammary glands it acts as a milk letting down hormone (Lactation)

(2) Vasopressin (ADH) – Target organ kidney, specifically the distal convoluted tubules of the nephrons Its function is stimulation of reabsorption of water, during deficit of water in the body.

Question 3.
What is endocrine gland? Name the hopiones secreted by the anterior lobe of pituitary gland and give one function each. (Oct. 85)
Answer:
Endocrine glands are ductless glands which are specialised invaginations of the surface epithelium elaborating and secreting chemical substances called hormones in small quantities into blood through which it is transported to respective target organs.

The pituitary gland produces a totally 9 hormones; 6 of them from the anterior lobe, 1 from the intermediate lobe and 2 from the posterior lobe. The list with one function each is given below.

(1) Growth hormone (GH) or Somototrophin: The basic function of this hormone is to stimulate body weight and rate of growth of the body in terms of muscle, bone structure, cartilage etc.

(2) Thyroid stimulating hormone (STH): regulates the growth of the thyroid gland and increase in thyroid activity.

(3) Adrenocortlcotrophic hormone (ACTH): Regulates the hormonal secretions of the Adrenal cortex (Steroid hormones) and Increase Adrenocortical activity.

(4) Gonadotrophic hormones: Stimulating the growth and activity of gonads

• Follicle stimulating hormone (FSH): stimulates ovarian follicular growth in female (Ovary) and stimulates the increased production of sperms in male (Testis – semiferous tubules)
• Luteinizing hormones (LH): Stimulates finai maturation of graafian follicle in the ovary. Along with FSH it also stimulates production of progesterone in females. ICSH- in males, it stimulates the testis to produce androgens.

(5) Prolactin (PRL): Stimulates growth of mammary glands and production of milk in females.

(6) Melanocyte – stimulating hormone: Stimulates the increased production of Melanin pigment and its dispersal in mammalian skin.

(7) Vasopressin (or Antidiuretic hormone – ADH): Acts on kidney tubules and controls the water (metabplism) balance, i.e. increases reabsorption of water in kidney tubules (distal part) whenever the body faces a deficit in water.

Question 4.
Why is the pituitary gland called as a master gland? What are the hormones secreted by it and their actions on the different organs of the body? (Mar. 89)
Answer:
The pituitary gland is called the ‘master gland’ due to the multiplicity of its functions and because its hormones control the growth and secretions of many other endocrine glands. [Note: For the second part of the question, refer answer Q. 1 in this section)

Question 5.
Mention any five hormones of Adenohypophysis with one function each? (April 91)
Answer:
The pituitary gland produces a totally 9 hormones; 6 of them from the anterior lobe, 1 from the intermediate lobe and 2 from the posterior lobe. The list with one function each is given below.

(1) Growth hormone (GH) or Somototrophin: The basic function of this hormone is to stimulate body weight and rate of growth of the body in terms of muscle, bone structure, cartilage etc.

(2) Thyroid stimulating hormone (STH): regulates the growth of the thyroid gland and increase in thyroid activity.

(3) Adrenocortlcotrophic hormone (ACTH): Regulates the hormonal secretions of the Adrenal cortex (Steroid hormones) and Increase Adrenocortical activity.

(4) Gonadotrophic hormones: Stimulating the growth and activity of gonads

• Follicle stimulating hormone (FSH): stimulates ovarian follicular growth in female (Ovary) and stimulates the increased production of sperms in male (Testis – semiferous tubules)
• Luteinizing hormones (LH): Stimulates finai maturation of graafian follicle in the ovary. Along with FSH it also stimulates production of progesterone in females. ICSH- in males, it stimulates the testis to produce androgens.

(5) Prolactin (PRL): Stimulates growth of mammary glands and production of milk in females.

(6) Melanocyte – stimulating hormone: Stimulates the increased production of Melanin pigment and its dispersal in mammalian skin.

(7) Vasopressin (or Antidiuretic hormone – ADH): Acts on kidney tubules and controls the water (metabplism) balance, i.e. increases reabsorption of water in kidney tubules (distal part) whenever the body faces a deficit in water.

Question 6.
Mention the hormones secreted by hypothalamus and stored in neurohypophysis Add a note on their function. (Oct. 85)
Answer:
The hormones secreted by hypothalamus and stored in the neurohypophysis are the Oxytocin and Vasopressin (or ADH)

Oxytocin: The main function of oxytocin is aiding in child birth or parturation by acting on the smooth muscles lining the uterus and bringing about the contraction of the uterus required for parturation. It also, brings about contraction of the smooth muscles in the body but to a negligible intensity. Oxytocin also acts as a milk letting down hormone by acting on the mammary glands after parturation by stimulating Lactation in these glands. Apart from this, it acts on the adenohypophysis to induce production of Luteotrophic hormone which intern causes milk secretion.

Vasopressin (or ADH):
Its primary or basic function is to increase the reabsorption of water in the kidney tubules (or more precisely the distal convoluted tubule) whenever the body faces a deficit in water. Since this exhibits antidiuretic properties its also called as the Antidiuretic hormone. Deficiency of this hormone causes unnecessary and excess

Question 7.
Match the following

(a) Pars distalls – (i) Peptid.
(b) Pars nervosa – (ii) Thyroid
(c) Thyrocalcitonin – (iii) Anterior pituitary
(d) Insulin – (iv) Steroids
(e) Cortisol – (v) Posterlon pituitary
Answer:
(a) – (iii)
(b) – (v)
(c) – (ii)
(d) – (i)
(e) – (iv)

Question 8.
Fill in the blanks:
(a) …….. hormone decreases blood pressure.
(b) …….. hormone stimulates RBC production
(c) Thymosins provide ……..and …….. immunity.
(d) Enlargement of thyroid gland is called as ……..
(e) Catecholamines are …….. and ……..
Answer:
(a) Atrial natriuretic factor (ANF)
(b) Cortisol
(c) Cell mediated, humoral
(d) Goitre
(e) Adrenaline, noradrenaline

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Vachanagalu Questions and Answers, Notes, Summary

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1st PUC Chemistry The P-Block Elements One Mark Questions and Answers

Question 1.
Why does carbon show maximum catenation among group 14 elements?
Answer:

1. Small size of carbon atoms.
2. C-C bond energy is comparable with the bond energy between carbon and other element
3. 4 valency electrons are present in four orbitals and the tetravalency of carbon is fully saturated.

Question 2.
Name different types of charcoal.
Answer:
Wood charcoal, Animal charcoal, Sugar charcoal.

Question 3.
Give one use of black diamond.
Answer:
Due to their hardness, black diamonds are used in various cutting tools.

Question 4.
What type of hybridization does carbon undergo in diamond and graphite?
Answer:
In diamond sp³, in graphite sp².

Question 5.
Silicon has become a vital element in the modern electronics industry. Why?
Answer:
It can function as semiconductors especially as n-type and p-type extrinsic semiconductors lubricants and insulators, Silicons are used for making water-proof papers by coating them with a thin layer of silicons.

Question 6.
What is catenation?
Answer:
Carbon atoms have a remarkable property of joining with one another in a large number to form a long chain and rings. This property is known as catenation or self linkage.

Question 7.
What is the technique used in preparing very pure silicon?
Answer:
Zone refining.

Question 8.
Give an example for intrinsic semiconductor other than silicon.
Answer:
Germanium in the pure state.

Question 9.
Who discovered fullerene 7
Answer:
Richard E. Smalley, Robert F. Curl Jr. and Harold W. Kroto.

Question 10.
What kind of semiconductor is obtained when a little of phosphorus is added to silicon?
Answer:
n- type semiconductor.

Question 11.
Name the oxidation states exhibited by Ge, Sn, and Pb.
Answer:
+2 and +4

Question 12.
What type of semiconductor is obtained by doping germanium with indium?
Answer:
p-type semiconductor

Questuon 13.
Mention the catenation capacity of Si.
Answer:
16.

Question 14.
Why is boron metalloid?
Answer:
Boron resembles both with metals and non-metals therefore, it is metalloid

Question 15.
Give two important ores of boron.
Answer:

1. Borax, Na₂B₄O₇10H₂O
2. Kemite, Na₂B₄O₇2H₂O

Question 16.
Name two isotopes of boron
Answer:
are isotopes of boron.

Question 17.
Name two allotropes of boron.
Answer:
Amorphous and crystalline.

Question 18.
Why does boron not form B3⁺ ion?
Answer:
Boron does not form B³⁺ ion due to smallest atomic size and highest ionization energy

Question 19.
Why is crystalline boron hard solid?
Answer:
It is due to strong covalent bonds.

Question 20.
Why is boron used in nuclear reactors?
Answer:
Bonor can absorb neutrons.

Question 21.
What is tincal ? Give its chemical formula.
Answer:
Tincal (or Borax) is an ore of boron. Its formula is NaB₄ Or 10H₂O

Question 22.
Why does boron resemble Si?
Answer:
Both have similar charge over radius ratio, i.e., similar polarizing power.

Question 23.
Why does boron form stable electron deficient compounds?
Answer:
Boron has three valence electrons, it will share three electrons with other elements to form electron deficient compounds which are stable.

Question 24.
Why is boric acid (H₃BO₃) monobasic acid?
Answer:
It accepts a pair of electrons from OH^– ion of H₂O therefore, it is monobasic acid.

Question 25.
What type of glass is obtained when borax is added ?
Answer:
Pyrex glass is a glass which is heat resistant. It can withstand high temperature.

Question 26.
What is use of diborane? Why BHs exists in form of diborane ?
Answer:
BH₃ exists in form of diborane (B₄H₆) because it is electron deficient. Diborane is used as reducing agent.

Question 27.
Complete the following
(i) B + O₂ →
(ii) B + N₂ →
(iii) B + Cl₂ →
(iv) BF3 + NH₂ →
(v) Na₂B₄O₇+H₂O →
(vi) Na₂B₄O₇ →
Answer:
(i) 4B + 3O₂ → 2B₂O₃

Question 28.
Why does \(\mathrm{BF}_{6}^{3-}\) not exist?
Answer:
It is because ‘B’ does not have vacant d-orbitals.

Question 29.
Which type of bonds are formed by boron and why?
Answer:
Boron forms covalent bonds because it cannot lose electrons or gain electron easily.

Question 30.
What is basic structural unit of orthoboric acid? Name type of bond present in them.
Answer:
\(\mathrm{BO}_{3}^{3-}\) is basic structural unit of boric acid. Covalent bonds are present.

Question 31.
Give structure of diborane.
Answer:

Question 32.
Why do boron halides form addition compounds with ammonia and amines?
Answer:
It is because they are electron deficient.

Question 33.
In which pure form does carbon exists in nature?
Answer:
Fullerene

Question 34.
Give structure of CO₂.
Answer:
O = C = O, It has linear structure.

Question 35.
What name is given to the compounds formed by more electropositive elements with carbon?
Answer:
Ionic compounds

Question 36.
Is carbon dioxide poisonous or not?
Answer:
No, it is not poisonous.

Question 37.
What is producer gas ?
Answer:
Producer gas is mixture of CO and N₂ in the ratio of 2 : 1

Question 38.
Buckminster fullerene is a crystalline allotrope of which element ?
Answer:
Carbon

Question 39.
What is state of hybridisation of C in \(\mathrm{co}_{3}^{3-}\) ?
Answer:
‘C’ in \(\mathrm{co}_{2}^{3-}\) has sp² hybridisation.

Question 40.
How does BF₃ act as catalyst in industrial process?
Answer:
BF₃ is electron deficient, therefore acts as catalyst in industrial processes.

Question 41.
Why is BF₃ weaker Lewise acid than BCl₃
Answer:
BF₃ is weaker Lewis acid than BCl₃ because of more effective bonding in case of F due to smaller size, than Cl.

Question 42.
Name the elements present in boranes.
Answer:
Boranes are made up of boron and hydrogen.

Question 43.
Write the state of hybridization in BF₃.
Answer:
‘B’ in BF₃ has sp² hybridisation

Question 44.
Why does boric acid act as Lewis acid ?
Answer:
It is because in boric acid, boron does not have its octet complete. It accepts OH- from
water in aqueous solution B(OH)₃ + H₂O → [B(OH)₄]^– + H⁺

Question 45.
Why does boron form electron deficient compounds ?
Answer:
It is because boron has three valence electrons. It shares three electrons and gets six electrons, i.e., its octet is not complete. Therefore, it forms electron deficient compounds.

Question 46.
Mention the chief reason for the anomalous behaviour of boron in group 13 of the periodic table.
Answer:
It is due to small size and higher ionization energy and high charge/size ratio of boron.

Question 47.
Mention the type of hybrid orbitals of silicon in \(\mathrm{SiF}_{6}^{2-}\) ion.
Answer:
sp³d²

Question 48.
Mention the state of hybridization of B in \(\mathrm{BH}_{4}^{-}\)
Answer:
sp³

Question 49.
How is that silicon atoms can have a co-ordination number more than four but carbon atoms cannot?
Answer:
Silicon has vacant d-orbitals, therefore, it can have coordination number more than four but carbon cannot have because it does not have vacant d-orbitals.

Question 50.
CO₂ is gas while SiO₄ is solid at room temperature. State a reason for this.
Answer:
CO₂ exists as decrete molecules, therefore, it has weak Van der Walls’ forces for attraction whereas SiO₂ is three dimensional covalent solid.

Question 51.
Between AIF₃ and AICl₃ which one will have a higher melting point.
Answer:
AIF₃ is more ionic, therefore, has higher melting point.

Question 52.
Why is that aluminium metal cannot be obtained by electrolysis of an aqueous solution of a salt of aluminium?
Answer:
It is because aluminium metal reacts with water at high temperature.

Question 53.
Which one of the following elements +1 oxidation state as well: Al, B, Ca, Tl, Be?
Answer:
TI shows +1 oxidation acid.

Question 54.
Carbon and Silicon are mainly tetravalent but Ge, Sn and Pb show divalency. Give reason.
Answer:
Ge, Sn, Pb are divalent due to inert pair effect which is not there in carbon and silicon.

Question 55.
What property of anhydrous AlCl₃ makes it a very good preparative reagent in organic chemistry?
Answer:
It acts as Lewis acid.

Question 56.
Although pure silicon is an insulator, then how does it behave as semiconductor on heating?
Answer:
Silicon becomes semiconductor on just heating because electrons becomes free to move.

Question 57.
What is name given to elements which are neither metals nor non-metals?
Answer:
Metalloids

Question 58.
What is general formula of silicones ?
Answer:
R₂SiO is general formula of silicones.

Question 59.
What is the oxidation state of Ni in [Ni(CO)₄]?
Answer:
Ni has oxidation state of zero in [Ni(CO)₄]

Question 60.
What is inert pair effect ?
Answer:
The pair of electrons in valence s-orbital is reluctant to take part in bond formation due to poor shielding effect of -d and f-electron in heavier elements. It is called inert pair effect due to which lower oxidation state becomes more stable than higher oxidation state in case of p-block elements.

Question 61.
How are linear silicones obtained ?
Answer:
Linear silicones are obtained by hydrolysis of R₂SiCl₂ (chlorosilanes)

Question 62.
In terms of atomic size, ionization energy and charge, explain why are ionic compounds containing B³⁺ not formed.
Answer:
Boron has smaller atomic size, therefore, it cannot lose three electrons because its third ionization energy is very high.

Question 63.
Why does C differ from rest of elements ?
Answer:
Carbon has smallest size, highest ionization energy and high electro negativity, therefore, it differs from rest of the elements.

Question 64.
What are silicates?
Answer:
Silicates are minerals which consist of \(\mathrm{SiO}_{4}^{4-}\) units arranged in different ways.

Question 65.
Write the formula of inorganic benzene.
Answer:
B₃N₃H₆

Question 66.
Explain the following statement with reason.
The fullerene is considered as purest allotrope of carbon.
Answer:
It is because it does not have edges, therefore, impurities cannot be absorbed on it.

Question 67.
Mention the nature of an aqueous solution of borax.
Answer:
Basic in nature.

Question 68.
Boric acid is polymeric. Why?
Answer:
The presence of hydrogen bonds makes it polymeric.

Question 69.
Mention the type of hybridization of boron in diborane.
Answer:
Sp³

Question 70.
Which is thermodynamically most stable form of carbon ?
Answer:
Graphite

Question 71.
State the trends observed in case of each of the following: Oxidation state of the elements of Group 14.
Answer:
Group 14 elements show +2 and +4 oxidation states. Tendency to show +2 oxidation state increases down the group due to inert pair effect.

Question 72.
How does the boric acid polymerise ?
Answer:
Through hydrogen bonding.

Question 73.
Does BH₃ exists?
Answer:
No.

Question 74.
How does boron interact with NaOH ?
Answer:
2B + 6NaOH → 2Na₃B0₃ +3H₂

Question 75.
What is the oxidation state of C in
(a) CO
(b) HCN
(c) H₂CO₃
(d) CaC₂.
Answer:
(a) +2, (b) +2, (c) +4, (d) -1

Questuon 76.
Give two examples of electron-deficient compounds.
Answer:
BF₃ and B₃H₆.

Question 77.
Arrange the following halides of boron in the increasing order of acidic character. BF₃, BCI₃, BBr₃, BI₃.
Answer:
BF₃ < BCI₃ < BBr₃ < BI₃.

Question 78.
Which form of carbon is used to decolourise sugar ?
Answer:
Bone charcoal.

Question 79.
What does we get when Cone. H₂SO₄ is dropped on sugar ?
Answer:
Sugar Charcoal.

Question 80.
What happens when a borax solution is acidified ? Write a balanced equation for the reaction.
Answer:
Boric acid is formed (Na₂B₃O₇ + 2HC1 + 5H₂)O →2Nacl + 4H₃BO₃

1st PUC Chemistry The P-Block Elements Two Marks Questions and Answers

Question 1.
Give the chemical reaction as an evidence for each of the following observation?

• Tin (II) is a reducing agent whereas lead (II) is not
• Gallium (I) undergoes disproportionation reaction.

Answer:

• It is because Pb²⁺ is more stable than Pb⁴⁺ due to inert pair effect whereas Sn⁴⁺ is more stable than Sn²⁺. Therefore Sn²⁺ is good reducing agent 3Ga⁺ —> 2Ga + Ga³⁺
• It is because Ga³⁺ is more stable than Ga⁺

Question 2.
Write the chemical equation for the reactions which occur when : R₂SiCl₂ is subjected to hydrolysis.
Answer:

Question 3.
Complete the following chemical reaction :
1. \(\mathrm{RCI}+\mathrm{Si} \frac{\text { Cupower }}{570 \mathrm{K}}\)
Answer:
2RC1 + Si → R₂SiCl₂

Questuon 4.
Describe two similarities and two dissimilarities between B and Al.
Answer:
Similarities :

1. Both have similar electronic configuration
2. Both have same number of valence electrons

Dissimilarities:

1. B is non-metal; Al is metal
2. B forms acidic oxide (B₂O₃) whereas Al form Al₂O₂ which is amphoteric

Question 5.
Draw a labelled diagram to show the dimeric structure of Al(III) chloride. State one use of anhydrous AICl₃.
Answer:
The structure of AICl₃ is shown below.

It issued in preparation of organic compounds in Friedal Crafts reaction.

Question 6.
Arrange the following compounds in decreasing order of property indicated against each. Give reason for your answer : BCI₃, AICl₃, GaGL₃, InCl₃, TiCl₃ (Stability of +3 oxidation state)
Answer:
BCl₃ > AICl₃> GaCl₃ > InCl₃ > TiCl₃ because of inert pair effect stability of +3 oxidation state decreases.

Question 7.
Discuss the diagonal relationship of Be and Al with regard to

• the action of alkali and
• the structure of the chlorides.

Answer:
Be and Al resemble with each other due to same charge over radius ratio.

• Both B and A1 amphoteric oxides
• Be and A1 form covalent compounds
• BeCl₂ exists as polymer whereas AICl₃ exists as dimmer
• Both Be and A1 react with NaOH to form similar compounds.

Question 8.
C and Si are always tetravalent but Ge, Sn, Pb show divalency.
Answer:
Ge, Sn, Pb show divalency due to inert pair effect, Pb²⁺ is more stable than Pb⁴⁺.

Question 9.
Which of the following is acidic and why: SiCO₂, AI₂O₃, PbCO₂, SiCO₂?
Answer:
SiCO₂ is acidic oxide because Si is non-metal.

Question 10.
As we move down in group 13 elements increase in atomic size is comparatively very less. Explain.
Answer:
It is due to poor shielding effect of d and f-electrons, as result of which effective nuclear charge increase.

Question 11.
Write the chemistry involved in etching of glass.
SiO₂ + 4HF → SiF₄ + 2H₂O
Answer:
SiF₄ +2HF → H₂SiF₆(Fluorosilicicacid)

Question 12.
Elemental silicon does not form graphite like structure as carbon does. Give reason.
Answer:
It is because ‘Si’ cannot form pπ-pπ bond like carbon in graphite due to larger atomic size.

Question 13.
What are silicones ?
Answer:
Silicones are rubber like polymers.

Question 14.
Give the shapes of
(a) SiF4,
(b) \(\mathrm{SiF}_{6}^{2-}\)
Answer:

Questuon 15.
Arrange the following in decreasing order of boiling point giving reason CH₄, GeH₄, SnH₄, SiH₄
Answer:
SnH₄ > GeH₄ > SiH₄ > CH₄
As we go down the group from C to Sn surface area of hydrides increases therefore, Van der Waals’ force increases hence boiling point increases.

Question 16.
Explain the following: (a) CaO reacts with SiCO₂ to form a slag.
Answer:
(a)

1st PUC Chemistry The P-Block Elements Threer / Four / Five Marks Questions and Answers

Question 1.
What are allotropy ? Mention allotropy of Pb, Sn, Ge, Si.
Answer:
Allotropy: The existence of same element in two or more forms in the same physical state but having different properties called allotropy. The different forms are called allotrope.
Pb : —> No allotrope exists.
Sn : —> Grey ( ) = White ( ) = ; Rhombic { Tin Cry : the sound when crystals of tin is Bent or deformed}
Ge : —> Two (Both are crystalline form.)
Si: —> Two ( Both are crystalline form.)

Question 2.
Explain the oxidation property of group 14 elements.
Answer:
Group 14 elements show commonly +2 and +4 oxidation state. The carbon family also shows both positive and negative oxidation state. It shows +2 oxidation state when np² electrons involved in the bond formation Ex-SnCl₂, PbSO₄. This show +4 oxidation state when ns²np² electrons involved in the bond formation. Ex-SnCl₄

Question 3.
Explain semiconductors with its types and uses.
Answer:
Semiconductors are the materials their conductance is lies between those of conductors and insulators. They allow only a certain portion of the current to pass through them. Materials used for semiconductors should be extremely pure and is obtained by zone refining.

Question 4.
Explain the types of semiconductors.
Answer:
1. Intrinsic Semiconductors: If Si of Ge is sufficiently heated the energy supplied breaks some of the covalent bonds and electrons become free to carry current. When the electrons are get free are released, positive holes are left behind in the lattice. In intrinsic semiconductors, the number of holes and electrons will be equal.

2. Extrinsic semiconductors: These are formed doping (addition of impurities of certain elements) to the insulators.

Question 5.
Explain the types Of Extrinsic Semiconductors
Answer:
I. n-type semiconductor: Doping of (Group 14 elements) Si, Ge, with pentavalent impurities (group 15 elements) like P. As, produces excess of electron and they are called n-type semiconductors. The symbol ‘n’ indicates the flow of negative charge in them.

Question 6.
How does metallic character vary among the group 14 elements? How is it related to ionisation energy?
Answer:
Carbon and silicon are non metals. Germanium is a metalloid and tin and lead are metals. Metallic character increases from carbon to lead. The change from non metallic to metallic character is due to the increase in atomic size from carbon to lead. Consequently the ionization potential decreases from carbon to lead.

Hence the electropositive character increases favouring ionic bonding especially with oxidation state +2. Whereas carbon and silicon show +4 oxidation state forming covalent bonding with electron sharing.

Question 7.
Distinguish between n- type and p – type semiconductors.
Answer:
n – type semiconductors are formed by doping pure Si or Ge with pentavalent elements like P, As, Sb, etc, Of the five valence electrons of the added elements, four of them form covalent bonds with Si (or Ge). The fifth electron, conducts the current.

In p – type conductor Si or Ge is doped with trivalent elements like Boron, aluminum or indium. The three valence electron of the added element form three covalent bonds with Si (or Ge) results as deficiency of one electron in the added element causes a positive hole. This type of extrinsic semiconductors are known as p – type semiconductors ( p – stands for positive hole).

Question 8.
How do you account for the tetravalency of carbon even though there are only 2 unpaired electrons ?
Answer:
Electronic configurations of carbon atom in the ground state is \(1 \mathrm{s}^{2} 2 \mathrm{s}^{2} 2 \mathrm{P}_{2}^{1} 2 \mathrm{P}_{2}^{1} 2 \mathrm{P}_{2}^{0}\) During the formation of a compound the activation energy of the reactants excites the electrons to give the configuration as \(1 \mathrm{s}^{2} 2 \mathrm{s}^{1} 2 \mathrm{p}_{\mathrm{x}}^{1} 2 \mathrm{p}_{\mathrm{y}}^{1} 2 \mathrm{p}_{\mathrm{z}}^{1}\) Then four orbitals each containing an impaired electron, mix together and form four hybridized sp³ orbitals directed from the carbon atom tetrahedrally. Hence carbon exhibits tetravalency.

Question 9.
How do the conductivity or semic conduction can be increased?
Answer:
As the temperature increases, the number of covalent bonds ruptured in an intrinsic semiconductor increases. This results in the increase of the electron hole pairs. As a result, the conductivity of the intrinsic semiconductor increases with rise in temperature. When electron field is applied across these materials electron migrate in one direction and the positive holes migrate is the opposite direction and thus the material conducts. At a given temperature the conductivity of an intrinsic semiconductor is constant.

Conductivity of a semiconductor can be increased by adding either pentavalent or trivalent elements. The elements added to intrinsic semiconductors to increase conductivity are called dopants, the process of addition of dopants (impurities) is called doping. The dopped semiconductors are called extrensic Semiconductors.

Question 10.
Write a note on structure of Fullerene. Mention any two of its application.

Answer:
Richard E. Smalley; Robert F. Curl Jr and Sir Harold W. Kroto the discoverers of this new form of pure carbon laked fullerene, they shared the 1996 Nobel Prize in chemistry for their discovery.

This third crystalline form of carbon discovered was named as buckminster fullerene which is commonly called fullerenes. They were named so because their structure resembles geodestic domes designed by the American scientist, engineer and philosopher R. Buckminster Fuller, They are also philosopher R. Buckminster Fuller. They are also nicknamed “Bucky ball” because their shape resembles a soccer ball.

Fullerenes are large spheroidal C_n molecules with n = 60 or more. When an electric arc is struck between graphite electrodes in an inert atmosphere a large quantity of soot is formed together with a significant quantity of C₆₀ and much smaller quantities of inter related fullerenes such as C₇₀ ; C₇₆ ; C₇₈.

When graphite is vapourised using a high power laser, fullerene C₆₀ is obtained. The fullerene C₆₀ bucky ball, has the same form as in soccer ball. In this each carbon atom is sp² hybridised. Each carbon atom has three neighbouring carbon atoms and forms two single and a double bond. C₆₀ has 32 faces. 20 of which are hexagons and 12 of which are pentagons. Each pentagon is surrounded by five hexagons and each hexagon is linked to three pentagons and each three hexagons. It has 60 vertices with a carbon atom at each vertex.

Question 11.
Write the characteristic uses of fullerene.
Answer:
C₆₀ dissolves in hydrocarbon solvents such as hexane, benzene, toluene etc giving magenta solutions. Fullerenes are the least stable of the carbon allotropes and graphite is the most stable. Fullerenes react with alkali metals to produce solids having composition such as K₃ C₆₀. This compound acts as a superconductor below 18K. Fullerene C₁₁₄ has more surface area and can withstand a very high temperature. Hence it can be used as a lubricant in satellites. Fullerenes are used as industrial catalyst and as lubricant in the treatment of cancer.

Question 12.
Explain the structure of graphite giving the reason for its softness as well as its electrical conductivity.
Answer:
Good conductor of electricity : In. graphite carbon atom is sp² hybridised. Out of four valiancy electrons in each carbon atom only three electrons, one from 2s and two from 2p are involved in hybridisation. One spare electron in its 2p_z orbital is left free. These 2p_z orbital overlap to form delocalised π system which extends above and below each layer. In this delocalised π electrons are free to move within the layer and hence graphite is a good conductor of electricity.

The conductivity of graphite perpendicular to the plane of the layers of hexagons is low and increases with increase in temperature, signifying that graphite is a semiconductor in that direction. The electrical conductivity is much higher parallel to the plane but decreases as the temperature is raised.

Soft, flaky and slippery substance : In graphite each layers of hexagon are held together by a weak Vander Waal’s force of attraction at a large distance of 3.40 Å. Even the slight pressure causes the layers to slide over one another. Hence graphite is soft, flaky and slippery. Graphite is used as a lubricant.

Question 13.
Explain the structure of diamond giving the reason for its hardness as well as non – conductivity of electricity.
Answer:
Non-conductor of electricity: All the four electrons present in the valence shell of carbon atoms are used up in sp³ hybridisation and form sigma bonds. No mobile electrons are left in the diamond crystals to allow the conduction of electricity. Hence diamond is a non-conductor of electricity.

Extremely hard: Due to high strength of covalent bonds holding all the carbon atoms in diamond together, diamond is very hard. Infact, diamond is the hardest substance known.

Question 14.
Give the difference in structure of the following pair of compounds : CO₂ and SiO₂.
Answer:
CO₂ linear molecule and exists as monomer. It is gas while SiO₂ is solid at room temperature due to three dimensional network in which each Si atom is covalently bonded to four oxygen atoms tetrahedrally. In CO₂, ‘C’ is sp-hybridised while in SiO₂, ‘Si’ is sp³ hybridised. CO₂ is discrete molecule where as SiO₂ is 3-dimensional solid.

Question 15.
Explain the formation of

(i) water gas
(ii) producer gas. Give their uses.
Answer:

Water gas and producer gas are used as fuel

Question 16.
What happens when CO₂ is passed through lime water
(i) for short duration
(ii) for a long duration ?
Answer:

Question 17.
The first element in every group of representative elements shows properties different from the characteristic properties of the group. Name three such elements and mention two abnormal properties of each one of them.
Answer:
Boron carbon Nitrogen
Boron

• W, forms acuhc. oxides -whereas owners item. am-phofork and.bask, oxide.
• It cannot form [BFe]^3′ whereas others can form such type of complexes.

Carbon:

• It shows property of catenation to maximum extent.

Nitrogen

• N₂ is gas others are solid
• NH₂ is liquid, other hydrides are gases.

Question 18.
Give equations for the following:

• Preparation of CO₂,
• Basic properties of Na₂CO₃,
• Formation of acetylene.

Answer:

• CaCO₃ + 2HC1 —> CaCl₂ + CO₂ + H₂O
• Na₂CO₃ + 2H₂0 —> 2Na0H + H₂CO₃
• CaC₂(calcium carbide) + 2H₂0 —>Ca(OH)₂ + C₂H₂(Acetylene)

Question 19.
What is dry ice ? Why is it called so? How will you prepare pure sample of CO (Carbon monoxide)?
Answer:
Solid CO₂ is called dry ice. It is called dry ice because it directly changes into gaseous state without becoming liquid.

Question 20.
What happens when ?

• Quick lime is heated with coke ?
• Carbon monoxide reacts with Cl₂?
• Plants absorb CO₂?

Answer:

• CaO + 3C —> CaC₂(CalciumCarbide) + CO,
• CO + Cl₂ —> COCl₂ (Phosgene)
• 6CO₂ + 6H₂O —> C₆H₁₂O₆(glucose) + 6O₂

Question 21.
Write balanced equations for the following reactions and name the main product formed in each case,

• NaBH₄ +I₂ —>
• B₂h₆ +NaH —>
• \(\mathrm{BF}_{3}+\mathrm{LiH} \stackrel{450 \mathrm{K}}{\longrightarrow}\)
• SiCl₄ + H₂O —>

Answer:

• 2NaBH₄ +I₂ —> 2Nal + +H₂ + B₂H₆ (Diborane)
• B₂H₆+2NaH —> 2NaBH₄ (sodium borohydride)
• 2BF₃ + 6LiH —> 6LiF + B₂H₆ (Diborane)
• SiCl₄ + 2H₂O —> 4HCl + Si(OH)₄ (Silicicacid)

Question 22.
Give a comparative account of the chemistry of carbon and silicon with regard to their

• property of catenation and
• stability of hybrids and oxides.

Answer:

• Carbon shows property of catenation to more extent than silicon due to small size and tendency to form pπ-pπ multiple bonds with itself
• Stability of hybrids : CH₄ is more stable than SiH4 due to small size of ‘C’.
• CO₄ is gas whereas SiO₂ is three dimensional covalent solid, therefore highly stable as compared to CO₂.

Question 23.
A certain salt X, gives the following results.
(i) Its aqueous solution shows alkaline to litmus paper
(ii) It swells up to a glassy material Y on strong heating
(iii) When cone H₂SO₄ is added to a hot solution of X, white crystal of an acid Z separates out-Write equations for all the above reactions and identify X, Y and Z.
Answer:

Question 24.
Write balanced equations for:

1. BF₃ + LiH →
2. B₂H₆ + H₂O →
3. NaH + B₂H₆ →
4. \(\mathrm{H}_{3} \mathrm{BO}_{3} \stackrel{\Delta}{\longrightarrow}\)
5. A1 + NaOH →
6. B₂H₆ + NH₃ →

Answer:

1. 2BF₃ +6LiH →B₂H₆ +6LiF

2. B₂H₆ + 6H₂O → 2B(OH)₃ + 6H₂

3. 2NaH + B₂H₆ → 2NaBH₄

4. \(\begin{array}{l}{\mathrm{H}_{3} \mathrm{BO}_{3} \stackrel{\Delta}{\longrightarrow} \mathrm{HBO}_{2}+\mathrm{H}_{2} \mathrm{O}} \\ {4 \mathrm{HBO}_{4} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{B}_{2} \mathrm{O}_{3}+2 \mathrm{H}_{2} \mathrm{O}}\end{array}\)

5. Al + 3NaOH → A1(0H)₃ +3Na

6. \(3 \mathrm{B}_{2} \mathrm{H}_{6}+6 \mathrm{NH}_{3} \stackrel{\text { heat }}{\longrightarrow} 2 \mathrm{B}_{3} \mathrm{N}_{3} \mathrm{H}_{6}+12 \mathrm{H}_{2}\)

Question 25.
Give one method for industrial preparation and one for laboratory preparation of CO and CO2 each.
Answer:

Question 26.
(a) Carbon dioxide is non-polar while water is polar. What conclusion do you draw about their structures from these.
(b) Classify the following compounds into acidic, basic and amphoteric oxides. Al₂O₃, Cl₂O₇
Answer:
is linear, bond moments are equal and opposite, net dipole moment is zero. Water is bent molecule, it has net dipole moment .

Al₂O₃ is amphoteric where Cl₂O₇ is acidic oxide.

Question 27.
A white crystalline solid ‘A’ dissolves in water to give an alkaline solution. On heating ‘A’ first loses water molecules and swells up. On further heating it turns into a transparent liquid which solidifies into a glassy bead.
Answer:
‘A’ is Borax i.e. Na₂[B₄O₅(OH)₄].8H₂O which is also written as.
The reactions are:

Question 28.
Boric acid is a weak acid. It acts as an acid only on first receiving OH- from the medium and then releasing H+ ions. From the following organic compounds; select the one in presence of which it acts as a strong acid. Glycerol, Ethylene, Ethylalcohol, Acetic Acid.
Answer:
It acts as a strong acid in presence of glyceol.
Reason: Acetic acid itself is an acid and cannot give OH^– ion, ethyl alcohol being a primary alcohol is alos acidic. Ethylene also can’t furnish OH^– ion. But glycerol that has 3-OH groups. One of which is a secondary -OH group can assist boric acid to release H+ ions.

Question 29.
A compound ‘X’ or reduction with LiAH4 gives a hydride ‘Y that contains 21.72% hydrogen along with other products. The compound ‘Y’ reacts with air explosively resulting in boron trioxide. Identify ‘X’ and ‘Y’. Give balanced reactions involved in the formation of ‘Y’ and its reactions with air. Draw the structure of Y.
Answer:
“X’ is BCl₃ Boron Trichloride Y is B₂H₆ as percentage of hydrogen given is 21.72%

Question 30.
Mention three important uses of borax.
Answer: It is used :

• as a flux soldering and welding industry
• in the manufacture of borosilicate glass (or pyrex glass)
• in making enamels and glazes
• in stiffening of candle wicks
• in softening of water
• in qualitative analysis for borax bead test in laboratory.

Question 31.
Mention some important properties of carbon monoxide.
Answer:
1. It is colourless, odourless gas, slightly soluble in water.

2. It is highly poisonous. It combines with haemoglobin in the red blood cells to form carboxy-haemoglobin which cannot absorb oxygen and thus supply of oxygen to the body is reduced.

3. It burns with a pale blue flame forming CO₂; i.e., 2CO + O₂ → 2CO₂

4. It is a reducing-agent. It reduced some metal oxides into metal,
Fe₂O₃ + 3CO → 2Fe + 3CO₂

5. It combines with transition metals like iron, cobalt, nickel to form their carbonyl compounds;

Question 32.
What are halides of carbon ? Give few examples.
Answer:
Carbon combines with halogens to form both simple and mixed tetrahalides. In case of simple halides all the four expected tetrahalides (e.g. CF₄, Cl₄, CBr₄ and Cl₄) are known to exist. The stability of the simple tetrahalides (CF₄ > CCl₄ > CBr₄ > Cl₄)
Amongst the mixed halides the better known compounds are
(CFCl₃,CF₂Cl₂ and CCl₃Br)

Question 33.
What is allotropy ? Give examples of allotropes.
Answer:
Two or more forms of the same elements in same physical state which differ in their physical properties but have same chemical properties are called allotropic forms or (allotropes) and the phenomenon is called allotropy.
Carbon, phosphorus and sulphur are some elements which exhibit allotropy.

• Diamond and graphite are allotropic forms of carbon
• Red phosphorus and white phosphorus are allotropes of phosphorus.
• Rhombic sulphur, monoclinic sulphur and plastic sulphur are allotropic forms of sulphur.

Question 34.
Draw the structure of
(a) anion cyclic silicates
(b) anion sheet silicates.
Answer:

Question 35.
Give three uses of different allotropic forms of carbon.
Answer:

Forms of carbon	Uses
Diamond	Gemstone, cutting, drilling, grinding, polishing, industry.
Graphite	Reducing agent, refractories, pencils, high temperature, crucibles, electrode making, moderator in nuclear reactors, high strength composite materials.
Activated carbon	Rubber industry, pigments in ink, paints and plastics
Coke	Fuel, strut manufacture
Charcoal	Fuel, reducing agent, Adsorption.

Question 36.
Write balanced equation for the following:
(i) BF₃ + LiH →
(ii) B₂H₆+H₂O →
(iii) NaH + B₂H₆ →
(iv) H₃BO₃ →
(v) A1 + NaOH + H₂O →
(vi) B₂H6 + NH₃ →
Answer:

Question 37.
Draw the structure of fullerene C₆₀
Answer:

Question 38.
Draw the structure of graphite.
Answer:

Question 39.
How does electron deficient compound BF₃ achieve electronic saturation i.e., the fully occupied outer electron shells ?
Answer:
1. By multiple bonding, e.g., BF3 in which a lone pair of electrons of each fluorine atom may be used in a B → F π-bond (back bonding) involving the vacant orbital on the boron atom.

2. By formation of complexes in which electrons are received from a donor molecule, e.g., F₃B → NH₃. Boron compounds, thus, behave as Lewis acids.

Question 40.
Compound X on reduction with LiAH4 gives a hydride Y containing 21.72% hydrogen along with other products. The compound Y reacts with air explosively resulting in boron trioxide. Identify X and Y. Give balanced equations involved in the formation of Y and its reaction with air. Draw the structure of Y.
Answer:
Step 1: To determine the molecular formula and structure of compound Y.
1. Since the hydride Y reacts with air forming boron trioxide, therefore, Y must be an hydride of boron.
2. %H = 21.72% (Given)

∴ Emperical formula of Y = BH₃
Since boron forms two types of hydrides, i.e., B_nH_n+4 (nidoboranes) and B_nH_n+6 (arachnoboranes), therefore, Y must be a nidoborane with n = 2. Thus, M.F of Y = B₂H₆ . If Y is B₂H₆ (diborane), then its structure must be as follows :

Bridges B…H = 134 pm Terminal B – H = 119 pm

Step 2: To determine the structure of the compound X.
Since compound Y i.e., B₂H₆ is formed by reduction of compound X with LiAH₄ ,
therefore, X must either BCl₃ or BF₃.

The equation representing the reaction of Y with O2 may be written as follows :
B₂H₆ + 3O₂ → 2B₂O₃ + 3H₂O
Diborane,Y
Thus X = BF₃ and Y = B₂H₆

Question 41.
How is boron obtained from boran? Give chemical equations with reaction conditions and its reaction with HCl₁
Answer:

Question 42.
Which one is more soluble in diethyl ether, anhydrous AlCl₃ or hydrous AICl₃ ? Explain in terms of bonding ?
Answer: An hydrous AICI₃ is an electron-deficient compound while hydrated AICI₃ is not. Therefore, anhyd. AICI₃ is more soluble in diethyl ether because the oxygen atom of either donates a pair or electrons to the vacant p-orbital on the A1 atom in AICI₃ forming a coordinate bond.

In case of hydrated AlCl₃. Al is not electron deficient since H₂O has already donated a pair of electrons to it.

Question 43.
Mention the structures of (CH₃)₃N and (Me₃Si)₃ N. Are they isostructural? Justify your answer.
Answer: (CH₃)₃ N is pyramidal involving sp³. hybridisation of N atom. Nitrogen in (Me₃Si)₃ is however, sp² -hybridized. The reason being that the p-orbit of N containing the lone pair of electrons overlaps with a vacant d-orbital of silicon. As a result of this pπ – dπ back bonding, (Me₃Si)₃ N is planar.

Question 44.
1. Describe with equation what happens when carbon is heated with cone. H₂SO₄ ?
2. State how will you separate C0₂ and S0₂ from the mixture?
Answer:
1. H₂S0₄ oxidies C to CO₂ and itself is reduced to SO₂

2. Since the O.N. of C is CO₂ is +4 which is the maximum for C, therefore, it cannot act as a reducing agent. In contrast the O.N. of S is SO₂ is also +4 but its maximum. O.N. +6, therefore, it can act as reducing agent. This reducing gas can be removed by passing the mixture of these gases through acidified K₂Cr₂O₇ solution when orange solution turns green due to reduction of \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\) ion to Cr³⁺ ions while CO₂ passes out unreacted.

Question 45.
What is inorganic benzene ? Why is it so called ? How will you get it from diborane?
Answer:
Borazine or borazole (B₃N₃H₆) is known as inorganic benzene. It is also called Because the structure of borazine is similar to that of benzene.
It is also isoelectronic and isosteric with benzene.

Like carbon is benzene, both N and B in borazine are sp² hybridized. Each N has a p-orbtal which is perpendicular to the a-bonding orbitals and contains a lone pair of electrons. In contrast, each B has an empty p-orbitals which is also perpendicular to the plane of the ring. Thus, the x-bonding in borazine is dative and it arises from the sideways overlap of fully filled orbitals of N and empty p-orbitals of B.

Preparation of borazine : At low temperature, diborane combines with ammonia to form an addition compound.
\(\mathrm{B}_{2} \mathrm{H}_{6}+2 \mathrm{NH}_{3} \stackrel{\text { Low Temp. }}{\longrightarrow} \mathrm{B}_{2} \mathrm{H}_{6} \cdot 2 \mathrm{NH}_{3}\)
When this addition compound is heated to 473 K, it decomposes to form a volatile compound called borazine.

Question 46.
State with equations what happens when borax is heated on a platinum wire loop and to the resulting transparent mass a minute amount of CuO is added and the mixture is again heated first in the oxidizing flame and then in the reducing flame of a Bunsen Burner ?
Answer:
When borax is heated on a platinum where loop, a transparent glassy bead is formed

When this transparent glassy bead is heated with CuO in the oxidizing flame, it imparts blue colour to the bead due to the formation of cupric metaborate
\(\mathrm{CuO}+\mathrm{B}_{2} \mathrm{O}_{3} \frac{\text { oxidising }}{\text { flame }} \mathrm{Cu}\left(\mathrm{BO}_{2}\right)_{2}\)(Cupric metaborate (blue)
However, when cupric metaborate is heated in the reducing flame of the Bunsen burner, the blue cupric metaborate is reduced by carbon present in the flame first to colourless cuprous metaborate and then to metal which produces red colour.

You can Download Chapter 21 Neural Control and Coordination Questions and Answers, 1st PUC Biology Question Bank with Answers, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka 1st PUC Biology Question Bank Chapter 21 Neural Control and Coordination

1st PUC Biology Neural Control and Coordination NCERT Text Book Questions and Answers

Question 1.
Briefly describe the structure of the following:
(a) Brain
(b) Eye
(c) Ear
Answer:
(a) Brain
The human brain is well protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of three layers namely outer durometer, middle layer called arachnoid and inner layer pia mater. The brain is divided into three major parts.

• Forebrain
• Mid brain
• Hindbrain.

Forebrain:
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum is divided longitudinally into two halves, left and right cerebral hemispheres. The hemispheres are connected by a tract of nerve fibres called corpus callosum. The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds. It is referred to as grey matter due to greyish appearance. The cerebral cortex contains motor areas, sensory areas and association areas which are responsible for complex functions like intersensory associations, memory and communication.

Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. This layer is white in colour, hence called white matter. The cerebrum wraps around a structure called thalamus, which is a major co-ordinating centre for sensory and motor signalling. Hypothalamus lies at the base of the thalamus and contains several group of neurosecretory cells, which secrete hormones called hypothalamic hormones. The inner parts of cerebral hemispheres and a group of associated deep structures like amygdala, hippocampus, etc. form a complex structure called the limbic lobe or limbic system.

(ii) Mid brain:
The midbrain is located between the thalamus / hypothalamus of the forebrain and pons of the hind brain. A canal called the cerebral aqueduct passes through the mid brain. The dorsal portion of the midbrain consists of four round swellings (lobes) called Corpora quadrigemina. Midbrain and hindbrain form the brain stem.

(iii) Hindbrain:
Hindbrain comprises pons, cerebellum and medulla. Pons consists of fibre tracts that interconnect different regions of the brain. Cerebellum has very convoluted surface in order to provide the additional space for many more neurons. The medulla of the brain is connected to the spinal cord.

(b) Eye:

The adult human eye ball is nearly a spherical structure. The wall of the eye ball is composed of three layers. The external layer called Sclera is composed of a dense connective tissue. The middle layer choroid contains many blood vessels and looks bluish in colour. The choroid layer is thin over the posterior two – thirds of the eyeball, but it becomes thick in the anterior part to form the ciliary body. The ciliary body continues to form a pigmented and opaque structure called the iris.

The eyeball contains a transparent crystalline lens which is held in place by ligaments attached to the ciliary body. The aperture surrounded by the iris is called the pupil. The diameter of the pupil is regulated by the muscle fibre of iris. The inner layer is the retina and it contains three layers of cells called ganglion cells, bipolar cells and photoreceptor cells. Rods and cones are two types of photoreceptor cells. The optic nerves leave the eye and the retinal blood vessels enter it at a point medial to and slightly above the posterior pole of the eye ball. Photoreceptor cells are not present in that region and hence it is called the blind spot.

At the posterior pole of the eye lateral to the blind spot, there is a yellowish pigmented spot called macula lutea with a central pit called the fovea. The fovea is a thinned out portion of the retina where only the cones are densely packed. It is the point where the visual activity is the greatest.

The space between the cornea and the lens is called the aqueous chamber and contains a thin watery fluid called aqueous humor. The space between the lens and the retina is called the vitreous chamber and is filled with a transparent gel called vitreous humor.

(c) Ear
Ear is divided into three major sections called the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and external auditory meatus. The external auditory meatus leads inwards and extends up to the tympanic membrane (ear drum). There are very fine hairs and wax- secreting sebaceous glands in the skin of the pinna and the meatus. The tympanic membrane is composed of connective tissues.

Covered with skin outside and with mucus membrane inside. The middle ear contains three ossicles called malleus, incus and stapes which are attached to one another in a chain-like fashion. The malleus is attached to the tympanic membrane and the stapes is attached to the oval window of the cochlea. An Eustachian tube connects the middle ear cavity with the pharynx.

The fluid filled inner ear called labyrinth consists of two parts, the bony and the membranous labyrinths. The bony labyrinth is a series of channels. Inside these channels lies the membranous labyrinth, which is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called cochlea.

The membranes consisting cochlea, the reissners and basilar, divide the surrounding perilymph filled bony labyrinth into an upper scala vestibuli and a lower scala tympani. The space within cochlea called scala media is filled with endolymph. At the base of the cochlea, the scala vestibuli ends at the oval window, while the scala tympani terminates at the round window which opens to the middle ear.

The organ of Corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors. The hair cells are present in rows on the internal side of the organ of Corti. The basal end of the hair ceil is in close contact with the afferent nerve fibres. A large number of processes called stereo cilia are projected from the apical part of each hair cell.

Above the rows of the hair cells is a thin elastic membrane called tectorial membrane. The inner ear also contains a complex system called vestibular apparatus, located above the cochlea. The vestibular apparatus is composed of three semicircular canals and the otolith organ consisting of the saccule and utricle. Each semi circular canal lies in a different plane at right angles to each other. The membranous canals are suspended in the perilyrrph of the bony canals. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris which has hair cells. The saccule and utricle contain a projecting ridge called macula.

Question 2.
Compare the following:
(a) Central neural system (CNS) and Peripheral neural system (PNS)
(b) Resting potential and action potential
(c) Choroid and retina
Answer:
(a) The central neural system (CNS) includes the brain and the spinal cord and is the – site of information processing and control. The PNS comprises of all the nerves of the body associated with the CNS (brain and spinal cord)

(b) Resting potential is the electrical potential difference across the resting plasma membrane. Here the outer surface of the axonal membrane is positively charged and inner surface is negatively charged and therefore is polarised.

The electrical potential difference across the plasma membrane, when the membrane is depolarised is called the action potential. Here the outer membrane is negatively charged and inner membrane is positively charged.

(c) Choroid layer is the middle layer of eye and is brownish black in colour. It is highly vascular and have pigments known as melanocytes which give colour to eye. Retina is the inner most and incomplete layer that extends up to ciliary body. The outer most layer of retina has two types of cells namely rods and cones.

Question 3.
Explain the following processes:
(a) Polarisation of the membrane of a nerve fibre
(b) Depolarisation of the membrane of a nerve fibre
(c) Conduction of a nerve impulse along a nerve fibre
(d) Transmission of a nerve impulse across a chemical synapse
Answer:
(a) Polarization of the membrane of a nerve fibre:

• When a neuron is not conducting any impulse, i.e., at rest the axon membrane is more permeable to potassium ions (K⁺).
• It is impermeable to sodium ions (Na⁺), negatively charged proteins and Cl^– ions.
• Consequently, the axoplasm inside the axon contains a high concentration of K⁺ and negatively charged proteins and low concentration of Na⁺.
• In contrast, the fluid outside the axon contains a low concentration of K⁺, a high concentration of Na⁺ and thus forms a concentration gradient. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na⁺ outwards for 2K⁺ into the cell.
• Asa result, the outer surface of the axonal ‘ membrane possesses a positive charge
  while its inner surface becomes negatively charged and therefore is polarised.
• The electrical potential difference across the resting plasma membrane is called resting potential.
• The electrical potential that occurs across the membrane of an axon, when stimulated by threshold stimulus is called depolarisation.

(b) Depolarisation of the membrane of a nerve fibre:

• When a stimulus is applied at a site on the polarised membrane, the membrane becomes more permeable to sodium ions (Na⁺) than to potassium ions (K⁺).
• The potential difference in the stimulated/ depolarised membrane is called an action potential.
• The action potential spreads like a wave along the membrane in the form of an impulse or spike.

(c)

Consider site A to be the site of excitation and hence depolarised. At sites immediately ahead, the axon (eg: site B) membrane has a .positive charge on the outer surface and a negative charge on its inner surface. As a result, a current flows on the inner surface from site A to site B. On the outer surface, current flows from site B to site A to complete the circuit of current flow. Hence, the polarity at the site is reversed, and an action potential is generated at site B. Thus, the impulse generated at site A arrives at site B. The sequence is repeated along the length of the axon and consequently, the impulse is conducted.

(d) A nerve impulse is transmitted from one neuron to another through junctions called synapses. At a chemical synapse, the membranes of the pre – and postsynaptic neurons are separated by a fluid-filled space called Synaptic cleft. Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses. When an impulse arrives at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane where they fuse with the plasma membrane and release their neurotransmitters in the synaptic cleft.

The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the post-synaptic neuron. The new potential developed may be either excitatory or inhibitory.

Question 4.
Draw labelled diagrams of the following:
(a) Neuron
(b) Brain
(c) Eye
(d) Ear
Answer:
(a) Neuron

(b) Brain
The human brain is well protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of three layers namely outer durometer, middle layer called arachnoid and inner layer pia mater. The brain is divided into three major parts.

• Forebrain
• Midbrain
• Hindbrain.

Forebrain:
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum is divided longitudinally into two halves, left and right cerebral hemispheres. The hemispheres are connected by a tract of nerve fibres called the corpus callosum. The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds. It is referred to as grey matter due to greyish appearance. The cerebral cortex contains motor areas, sensory areas and association areas which are responsible for complex functions like intersensory associations, memory and communication.

Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. This layer is white in colour, hence called white matter. The cerebrum wraps around a structure called thalamus, which is a major co-ordinating centre for sensory and motor signalling. Hypothalamus lies at the base of the thalamus and contains several group of neurosecretory cells, which secrete hormones called hypothalamic hormones. The inner parts of cerebral hemispheres and a group of associated deep structures like the amygdala, hippocampus, etc. form a complex structure called the limbic lobe or limbic system.

(ii) Midbrain:
The midbrain is located between the thalamus/hypothalamus of the forebrain and pons of the hindbrain. A canal called the cerebral aqueduct passes through the mid-brain. The dorsal portion of the midbrain consists of four round swellings (lobes) called Corpora quadrigemina. Midbrain and hindbrain form the brain stem.

(iii) Hindbrain:
Hindbrain comprises pons, cerebellum and medulla. Pons consists of fibre tracts that interconnect different regions of the brain. Cerebellum has very convoluted surface in order to provide additional space for many more neurons. The medulla of the brain is connected to the spinal cord.

(c) Eye:

The adult human eyeball is nearly a spherical structure. The wall of the eyeball is composed of three layers. The external layer called Sclera is composed of dense connective tissue. The middle layer choroid contains many blood vessels and looks bluish in colour. The choroid layer is thin over the posterior two-thirds of the eyeball, but it becomes thick in the anterior part to form the ciliary body. The ciliary body continues to form a pigmented and opaque structure called the iris.

The eyeball contains a transparent crystalline lens which is held in place by ligaments attached to the ciliary body. The aperture surrounded by the iris is called the pupil. The diameter of the pupil is regulated by the muscle fibre of iris. The inner layer is the retina and it contains three layers of cells called ganglion cells, bipolar cells and photoreceptor cells. Rods and cones are two types of photoreceptor cells. The optic nerves leave the eye and the retinal blood vessels enter it at a point medial to and slightly above the posterior pole of the eyeball. Photoreceptor cells are not present in that region and hence it is called the blind spot.

At the posterior pole of the eye lateral to the blind spot, there is a yellowish pigmented spot called macula lutea with a central pit called the fovea. The fovea is a thinned-out portion of the retina where only the cones are densely packed. It is the point where the visual activity is the greatest.

The space between the cornea and the lens is called the aqueous chamber and contains a thin watery fluid called aqueous humor. The space between the lens and the retina is called the vitreous chamber and is filled with a transparent gel called vitreous humor.

(d) Ear
Ear is divided into three major sections called the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and external auditory meatus. The external auditory meatus leads inwards and extends up to the tympanic membrane (eardrum). There are very fine hairs and wax- secreting sebaceous glands in the skin of the pinna and the meatus. The tympanic membrane is composed of connective tissues.

Covered with skin outside and with mucus membrane inside. The middle ear contains three ossicles called the malleus, incus and stapes which are attached to one another in a chain-like fashion. The malleus is attached to the tympanic membrane and the stapes are attached to the oval window of the cochlea. A Eustachian tube connects the middle ear cavity with the pharynx.

The fluid-filled inner ear called labyrinth consists of two parts, the bony and the membranous labyrinths. The bony labyrinth is a series of channels. Inside these channels lies the membranous labyrinth, which is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called the cochlea.

The membranes consisting cochlea, the reissners and basilar, divide the surrounding perilymph filled bony labyrinth into an upper scala vestibuli and a lower scala tympani. The space within cochlea called scala media is filled with endolymph. At the base of the cochlea, the scala vestibuli ends at the oval window, while the scala tympani terminates at the round window which opens to the middle ear.

The organ of Corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors. The hair cells are present in rows on the internal side of the organ of Corti. The basal end of the hair ceil is in close contact with the afferent nerve fibres. A large number of processes called stereocilia are projected from the apical part of each hair cell.

Above the rows of the hair cells is a thin elastic membrane called the tectorial membrane. The inner ear also contains a complex system called vestibular apparatus, located above the cochlea. The vestibular apparatus is composed of three semicircular canals and the otolith organ consisting of the saccule and utricle. Each semicircular canal lies in a different plane at right angles to each other. The membranous canals are suspended in the perilyrrph of the bony canals. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris which has hair cells. The saccule and utricle contain a projecting ridge called macula.

Question 5.
Write short notes on the following:
(a) Neural coordination
(b) Forebrain
(c) Midbrain
(d) Hindbrain
(d) Retina
(f) Ear ossicles
(g) Cochlea
(h) Organ of Cortl
(I) Synapse
Answer:
(a) Neural co-ordination: Co-ordination is the process through which two or more organs interact and complement the functions of one another. In our body the neural system and the endocrine system jointly coordinate and integrate all the activities of the organs so that they function in a synchronized fashion. The neural system provides an organised network of point-to-point connections for quick co-ordinations. Neural – co-ordination includes mechanisms like transmission of nerve impulse, impulse conduction across a synapse and reflex action.

(b) Forebrain:
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum is divided longitudinally into two halves, left and right cerebral hemispheres. The hemispheres are connected by a tract of nerve fibres called corpus callosum. The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds. It is referred to as grey matter due to greyish appearance. The cerebral cortex contains motor areas, sensory areas and association areas which are responsible for complex functions like intersensory associations, memory and communication.

Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. This layer is white in colour, hence called white matter. The cerebrum wraps around a structure called thalamus, which is a major co-ordinating centre for sensory and motor signalling. Hypothalamus lies at the base of the thalamus and contains several group of neurosecretory cells, which secrete hormones called hypothalamic hormones. The inner parts of cerebral hemispheres and a group of associated deep structures like amygdala, hippocampus, etc. form a complex structure called the limbic lobe or limbic system.

(c) Midbrain:
The midbrain is located between the thalamus/hypothalamus of the forebrain and pons of the hind brain. A canal called the cerebral aqueduct passes through the mid-brain. The dorsal portion of the midbrain consists of four round swellings (lobes) called Corpora quadrigemina. Midbrain and hindbrain form the brain stem

(d) Hindbrain:
Hindbrain comprises pons, cerebellum and medulla. Pons consists of fibre tracts that interconnect different regions of the brain. Cerebellum has very convoluted surface in order to provide additional space for many more neurons. The medulla of the brain is connected to the spinal cord.

(e) Retina: Retina is the inner layer of the eye and contains three layers of cells; ganglion cells, bipolar cells and photoreceptor cells, (from inside to outside respectively). There are two types of photoreceptor cells, namely rods and cones. These cells contain light-sensitive proteins called photopigments. Daylight vision and colour vision are functions of cones and the twilight vision is the function of the rods. The rods contain a purplish-red protein called the rhodopsin or visual purple, which contains a derivative of Vitamin A. There are three types of cones that respond to red, green and blue lights.

(f) Ear ossicles: The ear ossicles seen in the middle ear are malleus, incus and stapes. They are attached to one another in a chain-like fashion. Malleus is attached to the tympanic membrane and the stapes is attached to the oval window of the cochlea. The ear ossicles increase the efficiency of transmission of sound waves to the inner ear.

(g) Cochlear: The coiled portion of the labyrinth is called cochlea. The membranes constituting cochlea, the Meissner’s and basilar, divide the surrounding perilymph filled bony labyrinth into an upper scala vestibuli and a lower scala tympani. The space within cochlea called scala media is filled with endolymph. At the base of the cochlea, the scala vestibule ends at the oval window, while the scala tympani terminates at the round window which opens to the middle ear.

(h) Organ of Corti: The organ of Corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors. The hair cells are present in rows on the internal side of the organ of Corti. The basal end of the hair cell is in close contact with the afferent nerve fibres. A large number of processes called stereocilia are projected from the apical part of each hair cell. Above the rows of the hair cells is a thin elastic membrane called the tectorial membrane.

(i) Synapse: A nerve impulse is transmitted from one neuron to another through junctions called synapses. A synapse is formed by the membranes of a pre-synaptic neuron and a postsynaptic neuron, which may or may not be separated by a gap called the synaptic cleft. There are two types of synapses, namely, electrical synapses, the membranes of pre and post-synaptic neurons are in very close proximity. Electrical current can flow directly from one neuron into the other across these synapses.

The transmission of an impulse across electrical synapses is very similar to impulse conduction along a single axon. Impulse transmission across an electrical synapse is always faster than that across a chemical synapse. At a chemical synapse, the membranes of the pre and postsynaptic neurons are separated by a fluid-filled space called the synaptic cleft

Question 6.
Give a brief account of:
(a) Mechanism of synaptic transmission
(b) Mechanism of vision
(c) Mechanism of hearing
Answer:
(a) Mechanism of synaptic transmission: When an impulse reaches at the axon terminal, it stimulates the movement of the synaptic vesicles towards the synaptic cleft and releases their neurotransmitters. The neurotransmitter binds with the receptors found on the postsynaptic membrane. This binding opens ion channels allowing the entry of ions which can generate an action potential on the postsynaptic neuron.

(b) Mechanism of vision: The rays in visible wavelength focussed on the retina through the cornea and lens generate potentials (impulse) in rods and cones. The photo-sensitive compounds (photopigments) in the human eyes is composed of opsin and retinal. Light induces dissociation of the retinal from opsin resulting in changes in the structure of the opsin. This causes membrane permeability to change.

As a result, potential differences are generated in the photoreceptor cells. This produces a signal that generates action potentials in the ganglion cells through the bipolar cells. These action potentials are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analysed and the image formed on the retina is recognised based on earlier memory and experience.

(c) Mechanism of hearing: The external ear receives sound waves and directs them to the eardrum. The eardrum vibrates in response to the sound waves and these vibrations are transmitted through the ear ossicles to the oval window. The vibrations are passed through the oval window on to the fluid of the cochlea, where they generate waves in the lymph.

The waves in the lymphs induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair cells, pressing them against the tectorial membrane. As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognised.

Question 7.
Answer briefly:
(a) How do you perceive the colour of an object?
(b) Which part of our body helps us in maintaining the body balance?
(c) How does the eye regulate the amount of light that falls on the retina.
Answer:
(a) Cones are responsible for colour vision.
They require brighter light than rods. There are three types of cones, maximally sensitive to long wavelength, medium- wavelength, and short-wavelength light (often referred to as red, green, and blue, respectively, though the sensitivity peaks are not actually at these colours). The colour seen is the combined effect of stimuli to, and responses from, these three types of cone cells. When these cones are stimulated equally, a sensation of white light is produced.

(b) The inner ear has three semi-circular canals forming cochlea. The inner ear also contains a complex system called vestibular apparatus, located above the cochlea.
The vestibular apparatus is composed of three semi-circular canals and the otolith organ consisting of the saccule and utricle. The base of canals is swollen and is called ampulla, which contains a proj ecting ridge called crista ampullaris which has hair cells. The saccule and utricle contain a proj ecting ridge called macula. The crista and macula are the specific receptors of the vestibular apparatus responsible for maintenance of balance of the body and posture.

(c) The light rays in visible wavelength focussed on the retina through the cornea and lens generate potentials (impulses) in rods and cones.
Light induces dissociation of the retinal from opsin resulting in changes in the structure of the opsin.
This causes membrane permeability changes. As a result, potential differences are generated in the photoreceptor cells.
These action potentials are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analysed and the image formed on the retina is recognised based on earlier memory and experience.

Question 8.
Explain the following:
(a) Role of Na⁺ in the generation of action potential.
(b) Mechanism of generation of light-induced impulse in the retina.
(c) Mechanism through which a sound produces a nerve impulse in the inner ear.
Answer:
(a) Role of Na⁺ in action potential:

• At the point of stimulation, the membrane becomes freely permeable to . sodium ions (Na⁺).
• As sodium ions enter the axoplasm, the interior becomes positively charged and the exterior is negatively charged. 9.
• The positive ions travel from the depolarised region to the next polarised region through the axoplasm and create an action potential there.
• It results in forming wave of excitation along with the nerve fibre which is called nerve impulse.

(b) Mechanism of generation of light-induced impulse in the retina:

• Light induces the dissociation of retinal (an aldehyde of vitamin A) and opsin (a protein), this results in change in the structure of opsin.
• The permeability of the membrane changes as a result of the above dissociation.
• The potential differences generated in the photoreceptor cells produce a signal that generates action potential in the bipolar neurons.
• These impulses/action potentials are transmitted by the optic nerve to the visual cortex.
• The neural impulses are analysed and image formed is recognised based on the earlier memory and experience.

(c) Mechanism through which a sound produces a nerve impulse in the inner ear :

• The sound waves vibrate the eardrum.
• The vibrations produced in response to these waves are transmitted through the ear ossicles to the oval window from where they reach the fluid of the cochlea.
• The waves produced in the perilymph and endolymph induce a ripple in the basilar membrane.
• The movements of the basilar membrane bend the hair cells which press them against the tectorial membrane.
• Nerve impulses are generated in the associated afferent neurons.
• The afferent fibres transmit the impulses via auditory nerves to the auditory cortex of the brain where the impulses are analysed and the sound is recognised.

Question 9.
Differentiate between:
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Rods and cones
(d) Thalamus and Hypothalamus
(e) Cerebrum and Cerebellum
Answer:
(a) The myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. Myelinated nerve fibres are found in spinal and cranial nerves.

Unmyelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath around the axon, and is commonly found in autonomous and somatic nervous systems.

(b) Dendrites are short fibres which branch repeatedly and project out of the cell body. It also contains Nissl’s granules. These fibres transmit impulses towards the cell body. The axon is a long fibre, the distal and which is branched. Each branch terminates as a bulb like structure called synaptic knob which possesses synaptic vesicles containing chemicals called neurotransmitters. The axon transmit nerve impulses away from the cell body to a synapse orto a neuromuscular junction.

(c)

Rods	Cones
(i) Responsible for twilight vision.	(i) Responsible for daylight and colour vision.
(ii) More in number	(ii) Less in number
(iii) Respond to lower light intensity.	(iii) Sensitive to bright light
(iv) Absent in fovea centralis	(iv) Present in the fovea
(v) Contain pigment Rhodopsin	(v) Contain pigment iodopsin
(v) Contain pigment	(v) Contain pigment

(d) The cerebrum wraps around a structure called the thalamus, which is major coordinating centre for sensory and motor signaling. It functions as a relay station. Hypothalamus lies at the base of the thalamus. This portion contains a number of centres which control body temperature, urge for eating and drinking. It also contains several groups of neurosecretory cells, which secrete hormones called hypothalamic hormones.

(e)

Cerebrum	Cerebellum
(i)  Portion of fore brain. (ii) Seat of highest mental faculties, governs reasoning, learning, memory, intelligence (iii) Responds to heat, cold, pain, touch, light and pressure.	(i)  Portion of hind brain (ii) Regulates and coordinates the contraction of skeletal muscles. (iii) Maintains equili­brium and controls posture.

Question 10.
Answer the following:
(a) Which part of the ear determines the pitch of a sound?
(b) Which part of the human brain is the most developed?
(c) Which part of our central neural system acts as a master clock?
Answer:
(a) Organ of Corti
(b) Cerebrum
(c) Pineal gland

Question 11.
The region of the vertebrate eye, where the optic nerve passes out of the retina, is called the ………………….
(a) fovea
(b) Iris
(c) blind spot
(d) optic chiasma
Answer:
(c) blind spot

Question 12.
Distinguish between:
(a) afferent neurons and efferent neurons
(b) impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre
(c) aqueous humor and vitreous humor
(d) blind spot and yellow spot
(f) cranial nerves and spinal nerves.
Answer:
(a) The neuron which connects sense organs aw’ brain is called afferent neuron. The neuron which connects brain and effector organs or the concerned peripheral tissues  organs is called efferent neuron.

(b) In a myelinated neuron, impulse is transmitted by chemical method. It allows fast, saltatory movement of action potentials from node to node. In an unmyelinated neuron, impulse is transmitted by clerical mechanism. The conduction velocity of myelinated neurons vary linearly with axon diameter, whereas the speed of unmyelinated neurons vary roughly as the square root of the diameter of axons. Myelinated axon conduction is fast and energy efficient.

(c) The space between the cornea and the lens is called the aqueous chamber and contains a thin watery fluid called aqueous humor. The space between the lens and the retina is called the vitreous chamber and is filled with a transparent gel called vitreous humor.

(d) The optic nerves leave the eye and the retinal blood vessels enter it at a point medial to and slightly above the posterior pole of the eyeball called the blind spot. It doesn’t contain any photoreceptor cells (rods and cones). At the posterior pole of the eye lateral to the blind spot, is a yellowish pigmented spot called macula lutea (yellow spot). It contains cones only and the point where the visual acuity is the greatest

(e) Cranial nerves are the nerves that emerge directly from the brain stem in contrast to spinal nerves which emerge from segments of the spinal cord.

1st PUC Biology Neural Control and Coordination Additional Questions and Answers

1st PUC Biology Neural Control and Coordination One Mark Questions

Question 1.
What are meninges? (July 2011)
Answer:
The connective tissue membranes around brain are called meninges.

Question 2.
What is CNS?
Answer:
CNS or central nervous system is that includes brain and spinal cord.

Question 3.
What is Durometer?
Answer:
The outermost layer of meninges of CNS is Durometer.

Question 4.
What is corpus callosum?
Answer:
A transverse band of myelinated nerve fibers that connects cerebral hemispheres is called corpus callosum.

Question 5.
What is reflex arc? (June 2009)
Answer:
The path through which the electrochemical impulses are generated in response to a stimulus is called reflex arc.

Question 6.
What is reflex action?
Answer:
The quick, spontaneous and involuntary action induced by the nervous system in
response to a stimulus is called reflex action.

Question 7.
Which part of brain maintains body equilibrium? (Oct. 2000)
Answer:
Cerebellum is the centre for muscular coordination and equilibrium.

Question 8.
Name the protective covering of the brain. (April 2001)
Answer:
Meninges

Question 9.
Name the deep bridge of rieVve fibres which Joins cerebral hemispheres*. (Oct. 2003)
Answer:
Corpus callosum.

Question 10.
Name the structural and functional unit of nervous system. (July 2006)
Answer:
neuron

Question 11.
What is meant by co-ordination in our body?
Answer:
Co-ordination is the process through which two or more organs interact and complement the functions of one another.

Question 12.
What are afferent nerve fibers?
Answer:
The nerve fibres that transmit impulses from tissues / organs to the CNS are called afferent nerve fibres.

Question 13.
What are efferent fibres ?
Answer:
The nerve fibres that transmit regulatory impulses from the CNS to the concerned peripheral tissues / organs are called efferent nerve fibres.

Question 14.
Name the classification of autonomic neural system.
Answer:

• Sympathetic neural system
• Parasympathetic neural system

Question 15.
What are the major parts of a neuron ?
Answer:
Neuron is composed of cell body, dendrites and axon.

Question 16.
What are Nisei’s granules?
Answer:
Mr.’Nissl’s granules are certain granular bod¬ies present in the cytoplasm of the cell body of a neuron.

Question 17.
What are dendrites?
Answer:
Short fibres that branch repeatedly and project out of the cell body and also contain Nissl’s granules are called dendrites.

Question 18.
Where are neuro transmitters found ?
Answer:
Neurotransmitters are chemicals found in synaptic vesicles present in synaptic knob.

Question 19.
Name the three types of neurons.
Answer:
Multipolar, bipolar and unipolar neurons.

Question 20.
Where are multipolar neurons found in human body?
Answer:
Cerebral cortex …

Question 21.
What are nodes of Ranvier ?
Answer:
The gaps between two adjacent myelin sheaths of axon are called nodes of Ranvier.

Question 22.
Where exactly are synaptic vesicles located? What is their role ? (Foreign 2006)
Answer:
Synaptic vesicles are found in synaptic knob. They contain chemicals called neurotransmitters which are involved in transmission of impulses.

Question 23.
What are the charges on outer surface and Inner surface of axonal membrane during rest?
Answer:
Outer surface is positively charged and inner surface is negatively charged.

Question 24.
What are the functions of association areas?
Answer:
Association areas are responsible for complex functions like inter sensory associations memory and communication.

Question 25.
Write one function of limbic system in human brain. (Foreign 2006)
Answer:
Sexual behaviour, excitement, pleasure, rage, fear and motivation.

Question 26.
What is the canal passing through mid brain called?
Answer:
Cerebral aqueduct.

Question 27.
What is corpora quadrlgemina ?
Answer:
Corpora quadrigemina are four round swellings (lobes) found in the dorsal portion of midbrain.

Question 28.
Name the three regions of hindbrain.
Answer:
Pons, cerebellum and medulla.

Question 29.
What is the function of medulla oblongata.
Answer:
It contains centres which control respiration, cardiovascular reflexes and gastric secretions.

Question 30.
Which is the visible coloured portion of the eye ?
Answer:
Iris.

Question 31.
Name the external layer of the eye.
Answer:
Sclera

Question 32.
Name the area of retina which contains only cones and no rods. (Delhi 1997)
Answer:
Fovea

Question 33.
Why is blind spot devoid of the ability for vision?
Answer:
Blind spot does not contain any photoreceptor cells (rods and cones), hence devoid of vision.

Question 34.
Name the photosensitive compounds in human eye.
Answer:
Mropsin and retinal.

Question 35.
Name the fluid in which the membranous labyrinth of the inner ear floats. (Delhi 1997)
Answer:
Perilymph

Question 36.
Give the technical names of the auditory ossicles in their natural sequence. (All India 1997)
Answer:
Malleus, incus and stapes.

Question 37.
What connects the middle ear cavity with the pharynx?
Answer:
Eustachian tube.

Question 38.
Name the space within cochlea filled with endolymph.
Answer:
Scala media.

Question 39.
What does vestibular apparatus composed of?
Answer:
Three semicircular canals and otolith organ.

Question 40.
What is macula?
Answer:
The saccule and utricle contain a projecting ridge called macula.

Question 41.
Name the receptors responsible for body balance and posture.
Answer:
Crista and macula.

Question 42.
What is the function of Eustachian tube?
Answer:
It helps in equalising the pressures on either sides of the ear drum.

1st PUC Biology Neural Control and Coordination Two Marks Questions

Question 1.
What is reflex arc and reflex action.
Answer:
The path through which the electro-chemical impulses are generated in response to a stimulus is called reflex arc. It is the simplest functional unit of the nervous system by which an impulse produces a reflex action.The quick, spontaneous and involuntary action induced by the nervous system in response to a stimulus is called reflex action.

Question 2.
What are the functions of CSF.
Answer:

• It acts as a buffer, protecting the brain and spinal cord.
• It conveys nourishment to the tissues of the brain and spinal cord.
• It protects both brain and spinal cord from shocks and maintains constant pressure with in cranium.

Question 3.
Write the functions of hypothalamus.
Answer:

• Thermo regulation
• Biological clock system
• Autonomic nervous system control
• Sleep
• Controlling body temperature, appetite, secretion of pituitary.

Question 4.
What are Meninges? Mention different layers of Meninges.
Answer:
The connective tissue membranes around brain are called meninges. They protect the delicate nerve structure, carry the blood vessels to it and by the secretion of a fluid
(C S F) minimize any blow or concussion. There are three layers of Meninges;

• Durometer
• The arachnoid
• Piamater

Question 5.
What happens if the cerebellum is damaged. (Oct. 97)
Answer:
As the cerebellum is concerned with the maintenance of equilibrium of the body and coordination of contractions and relaxations of muscles, a damage to the, cerebellum leads to loss of the ability in muscular co-ordination and equilibrium in a person.

Question 6.
List any four functions of hind brain. (July 06)
Answer:
The functions of the hind brain are

• It regulates posture and postural activities.
• It plays an important part in muscular co ordination and maintenance of balance
• Cerebellar hemisphere controls muscle tone and posture on its side
• It regulates smooth and precise goal oriented movements.

Question 7.
Briefly give an account of somatic and autonomic nervous system.
Answer:
The PNS is divided into two divisions:

• Somatic neural system
• Autonomic neural system (ANS)

Somatic neural system relays impulses from the CNS to skeletal muscles while the autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body. The ANS is further classified into sympathetic neural system and parasympathetic neural system.

Question 8.
What are the functions of hypothalamus?
Answer:

• It controls body temperature, urge for eating and drinking.
• It contains cells that secrete hormones called hypothalamic hormones.
• It is involved in the regulation of sexual behaviour, expression, emotional reactions and motivation.

Question 9.
Write the difference between cerebrum and cerebellum
Answer:

Cerebrum	Cerebellum
(a) It is a part of forebrain (b)  It is meant for memory, intelli­gence and control of voluntary move­ments	(a)  It is a part of hindbrain (b)  It controls the move­ments and help in maintaining body posture.

Question 10.
Why are gray matter and white matter contained In human nervous system name so? (Delhi 2006)
Answer:
Grey matter:
It contains neural cell bodies (spindle, pyramidal and stellate neurons) which give them greyish appearance.

White matter:
This region contains millions of axons with myelin sheath which gives them an opaque white appearance.

Question 11.
Name and differentiate between two types of synapses. (Foreign 2004)
Answer:
The two types of synapses present are:

• Electrical synapse
• Chemical synapse

Electical synapse	Chemical synapse
(a)  Electrical current flows directly from one neuron to other. (b) Synaptic cleft is very narrow (c) Impulse transmis­sion is faster (d) These are less com­mon	(a)  Signal transmissions involve chemical called neurotransmit­ters. (b) Synaptic cleft is wider. (c)  Impulse transmission is slower. (d) These are more com­mon.

Question 12.
Name the ear ossicles in the order of arrangement in humans. What role do they play in hearing?
Answer:
Malleus, Incus, and Stapes are the ear ossicles. The vibrations due to sound waves are transmitted through the ear ossicles to the oval window which are further transmitted to endolymph.

Question 13.
What is blind spot? Why is it so named? (Foreign 2003)
Answer:
The point where optic nerves leave the eye and the retinal blood vessels enter which is slightly above posterior pole of the eye ball is called blind spot. It lacks photoreceptor cells (rods and cones) and is devoid of vision. Hence called blind spot.

Question 14.
What happens when the membrane of a nerve cell carries out a sodium pump? (Delhi 2001)
Answer:
When the membrane of a nerve cell carries out a sodium pump, it transports 3 Na⁺ ions outwards for 2 K⁺ ions into the cell. As a result, the outer surface of the axonal membrane posses a positive charge while its inner surface is negatively charged and therefore polarised.

Question 15.
What are the events that take place at the point of simulation of an axon? (Delhi 1997)
Answer:
When a stimulus is applied at a site on the polarised membrane, it becomes freely permeable to Na⁺. This leads to a rapid influx of Na⁺ which causes the outer surface of the membrane to be negatively charged and the inner side becomes positively charged i.e., depolarisation takes place.

Question 16.
What constitutes the outer ear. Mention one function of each.
Answer:
The outer ear consists of the pinna and external auditory meatus.

• Pinna collects the vibrations in the air which produce sound.
• There are very fine hairs and wax secreting sebaceous glands in the skin of pinna and the meatus.

1st PUC Biology Neural Control and Coordination Three Marks Questions

Question 1.
Draw a diagram to show the path followed by the nerve impulse from the receptor to the effector in a spinal reflex arc. Label any six parts. (All India 2004 )
Answer:

Question 2.
Where are synaptic vesicles found? Name their chemical contents. What Is the function of these contents?
Answer:
Synaptic vesicles are found in a bulb like structure called synaptic knob. Synaptic vesicles contain chemicals called neurotransmitters. Neurotransmitters are involved in the transmission of impulses at the synapses. They bind to the receptors present on the post – synaptic membrane and generate new potential.

Question 3.
Explain briefly the structure and function of human middle ear. (All India 1997 C)
Answer:
The middle ear contains three ossicles called malleus, incus and stapes which are attached to one another in a chain like fashion. The malleus is attached to the tympanic membrane and the stapes is attached to the oval window of the cochlea. An Eustachian tube connects the middle ear cavity with the pharynx.

Functions:

• The ear ossicles increase the efficiency of transmission of sound waves to the inner ear.
• Eustrachian tube helps in equalising the pressures on either sides of the ear drum.

Question 4.
Name the three types of neurons based on the number of axon and dendrites and give the location of their presence.
Answer:
(i) Unipolar neurons:

• Cell body with one axon.
• found in embryonic stage

(ii) Bipolar neurons:

• Cell body with one axon and one dendrite
• found in retina of the eye

(iii) Multipolar neurons:

• Cell body with one axon and two or more dendrites
• Found in cerebral cortex

Question 5.
Draw a diagram showing axon terminal and synapse and label any six parts
Answer:

Question 6.
Draw a neat labelled diagram of sectional view of cochlea.
Answer:

1st PUC Biology Neural Control and Coordination Five Marks Questions

Question 1.
List out the functions of different parts of the human brain. (April 97)
Answer:
The human brain has 3 main divisions namely Forebrain, Midbrain and Hindbrain. The Forebrain is composed (or subdivided into) of the cerebrum and diencephalon, the Midbrain is also called the mesencephalon with only one subdivision and the hind brain is composed of two subdivisions namely the cerebellem and medulla oblongata.
The functions of all these parts forming the brain are listed below:

(1) Forebrain (prosencephalon)

• Cerebrum – Is a functional center for intelligence, consciousness, voluntary control, memory.
•  Diencephalon- (Thalamus & hypothalamus) – While the thalamus acts as a main relay centre for conducting information, the hypothalamus controls the temperature of the body, appetite, fat metabolism, secretions of pituitary, sleep and the emotional states namely fear and anger.

(2) Midbrain (Mesencephalon) is the control centre for visual and auditory reflexes like adjustment of the ear to sound, pupil reflex, blinking etc.
(3) Hindbrain (Rhombencephalon)

• Cerebellum is the control centre for muscular coordination and equilibrium.
• Pons connects various parts of the brain with one another and contains the respiratory centres
• Medulla oblongata: contains the centres that control the heart beat, blood pressure, respiration and also centres that control swallowing, coughing and vomiting.

Question 2.
(i) A person unconsciously withdraws his hand suddenly with a jerk after touching hot plata- Draw a schematic diagram of the nervous pathway involved in the response.
(ii) What is such a response called?
Answer:
(i)

(ii) Such a response is called ‘reflex action’

Question 3.
Match the following:
I – II
(a) Depolarisation (i) Mid brain
(b) Polarisation (ii) Hind brain
(c) Corpus callosum (iii) Fore brain
(d) Corpora quadrigemina (iv) Action potential
(e) Pons (v) Resting potential
Answer:
(a) → (iv)
(b) → (v)
(c) → (iii)
(d) → (i)
(e) → (ii)

Question 4.
Fill In the blanks.
(a) The………….. fibres transmit impulses from tissues to the CNS and …………..fibres transmit Impulses from CNS to organs.
(b) The gaps between two adjacent myelin sheaths is called …………….
(c) …………….. are responsible for functions like memory and communication.
(d) The coiled portion of the labyrinth is called …………..
(e) ………….. contains hair cells that act as auditory receptors.
Answer:
(a) Afferent, Efferent
(b) Nodes of Ranvier
(c) Association areas
(d) Cochlea
(e) Organ of Corti

Question 5.
State whether the following statements are true / false. Correct the statements If false.
(a) Impulse transmission across electrical synapse is faster than that of chemical
synapse.
(b) During polarisation of axonal membrane, outer surface is negatively charged and inner surface is positively charged.
(c) Middle layer of cranial meninges is called pla mater.
(d) Cerebellum is responsible for controlling respiration and gastric secretions.
(e) Visible coloured portion of the eye Is Iris.
Answer:
(a) True.
(b) False; outer surface is positively charged and inner surface is negatively charged.
(c) False; middle layer is called arachnoid
(d) False; Medulla is responsible for controlling respiration and gastric secretions.
(e) True.

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Karnataka 1st PUC Biology Question Bank Chapter 20 Locomotion and Movement

1st PUC Biology Locomotion and Movement NCERT Text Book Questions and Answers

Question 1.
Draw the diagram of a sarcomere of skeletal muscle showing different regions.
Answer:

Question 2.
Define the sliding filament theory of muscle contraction.
Answer:
Sliding filament theory states that contraction of a muscle fibre takes place by the sliding of the thin filaments over thick filaments.

Question 3.
Describe the important steps in muscle contraction.
Answer:
Steps in muscle contraction:
A nerve impulse arriving at the neuromuscular junctions initiates the contractile response.

• A neurotransmitter released at the neuromuscular junction enters the sarcomere through its membrane channel.
• The opening of the channel also results in the inflow of Na+ ions inside the sarcomere and generates an action potential that travels along the entire length of the muscle fibres.
• The sarcomere reticulum releases Ca++ ions, which bind with the specific sites present on the troponin component of the thin filament.
• Asa result of conformational changes in the troponin, the active sites on the F-actin are exposed.
• These are the active sites specific to the myosin head, which exhibits myosin-dependent ATPase activity.
• The myosin heads act as hooks and attach to F-actin to form cross-bridges.
• When the muscle is stimulated to contract, the cross-bridges move, pulling the two filaments past each other.
• When thousands of actin and myosin filaments interact this way the entire muscle cell shortens.

This concept is the sliding filament theory.

Question 4.
Write true or false. If false change the statement so that it is true.

1. Actin is present in the thin filament
2. H-zone of striated muscle fiber represents both thick and thin filaments.
3. The human skeleton has 206 bones.
4. There are 11 pairs of ribs in man.
5. The sternum is present on the ventral side of the body.

Answer:

1. True
2. False; H – zone represents thick filaments.
3. True
4. False; There are 12 pairs of ribs.
5. True.

Question 5.
Write the difference between:
(a) Actin and Myosin
(b) Red and White muscles
(c) Pectoral and Pelvic girdle
Answer:
(a) Actin filaments are thinner as compared to the myosin filaments. Actin filament exists in two forms namely globular actin or G actin and fibrous actin of F- actin. It also contains two proteins namely tropomyosin and troponin. Myosin filament or myofibril consists of two portions, head, and tail. The head is formed of heavy meromyosin (HMM) and the tail is formed of light meromyosin (LMM). The myosin head possesses contractile property as well as ATPase activity.

(b) Red and White muscles
Answer:

Red Muscle	White Muscle
(a) Red in colour due to the presence of large amount of myoglobin (b) Thin (c) Slow and sustained contraction (d) Depend on aerobic metabolism for energy (e) Presence of large amount  of mitochondria (f) Perform sustained work for a long time. (g) Blood capillaries more, eg: Extensor muscle on the back of the human body.	(a) Lesser amount of myoglobin, hence white in colour (b) Thick (c) Contraction rate is fast (d) Depend  on anaerobic metabolism for energy (e) Presence of small amount of mitochondria (f) Perform strenuous work for a short time. (g) Blood capillaries less, eg: Muscles of the eyeball.

(c) Pectoral and Pelvic girdle
Answer:

Pectoral girdle	Pelvic girdle
(i) Connects forelimb with axial skeleton	(i) Connects leg with the axial skeleton
(ii) Each half is formed of two bones, clavide and scapula	(ii) Each half is formed  of three bones ilium, ischium and pubis
(iii) Two halves are not fused	(iii) Two halves are fused
(iv) Found in backside of thorax	(iv) Found in hip region
(v) Cavity is known as glenoid cavity.	(v) A cavity is known as acetabulum

Question 6.
Match Column I with Column II:

Column I – Column – II

(a) Smooth muscle – (I) Myoglobln
(b) Tropomyosin – (II) Thin filament
(c) Red muscle – (III) Sutures
(d) Skull – (lV) Involuntary
Answer:
(a) (iv)
(b) (ii)
(c) (i)
(d) (iii)

Question 7.
What are the different types of movements exhibited by the cells of the human body?
Answer:
Cells of the human body exhibit three main types of movements, namely, amoeboid, ciliary and muscular. Some specialized cells in our body like macrophages and leucocytes in blood exhibit amoeboid movement. It is affected by pseudopodia formed by the streaming of protoplasm (as in Amoeba). Cytoskeletal elements like microfilaments are also involved in the amoeboid movement.

Ciliary movement occurs in most of our internal tubular organs which are lined by ciliated epithelium. The coordinated movements of cilia in the trachea help us in removing dust particles and some of the foreign substances inhaled along with the atmospheric air. Passage of ova through the female reproductive tract is also facilitated by the ciliary movement. Movement of our limbs, jaws, tongue, etc, requires muscular movement. The contractile property of muscles is effectively used for locomotion and other movements by human beings and the majority of multicellular organisms. Locomotion requires a perfect coordinated activity of muscular, skeletal, and neural systems.

Question 8.
How do you distinguish between a skeletal muscle and a cardiac muscle?
Answer:
Skeletal muscle: Skeletal muscles are closely associated with skeletal components of the body. They have a striped appearance under the microscope and hence are called striated muscles. As their activities are under the voluntary control of the nervous system, they are known as voluntary muscles too. They are primarily involved in locomotory actions and changes in body postures.

Cardiac muscles: Cardiac muscles are the muscles of the heart. Many cardiac muscle cells assemble in a branching pattern to form a cardiac muscle. Based on appearance, cardiac muscles are striated. They are involuntary in nature as the nervous system does not control their activities directly.

Question 9.
Name the type of Joint between the following:

1. Atlas/axis
2. Carpal/metacarpal of the thumb
3. Between phalanges
4. Femur/acetabulum
5. Between cranial bones
6. Between pubic bones in the pelvic girdle

Answer:

1. Pivot joint
2. Saddle joint
3. Gliding joint
4. Ball and socket joint
5. Fibrous joint
6. Cartilaginous joint

Question 10.
Fill in the blank spaces:

1. All mammals (except a few) have ……………… cervical vertebra.
2. The number of phalanges in each limb of humans………………
3. A thin filament of myofibril contains 2 ‘F’ actins and two other proteins namely ……………… and ………………
4. In a muscle fibre Ca++ is stored in ………………
5. ……………… and pairs of ribs are called floating ribs……………….
6. The human cranium Is made of ………………bones.

Answer:

1. 7
2. 14
3. Troponin and Tropomyosin
4. Sarcoplasmic reticulum
5. 11 and 12
6. 8

1st PUC Biology Locomotion and Movement Additional Questions and Answers

1st PUC Biology Locomotion and Movement One Mark Questions

Question 1.
Name two sites in our body where ciliary movement is seen.
Answer:
Fallopian tube and trachea.

Question 2.
Give two examples of movements that involve muscular movement.
Answer:
Movement of limbs, jaw, tongue etc.

Question 3.
Why are striated muscles called skeletal muscles?
Answer:
Striated muscles are attached to bones and so-called skeletal muscles.

Question 4.
Mention two sites on our body where striated muscles are present.
Answer:
Limbs and tongue.

Question 5.
Why are smooth muscles called visceral muscles?
Answer:
Smooth muscles are located in the inner walls of hollow visceral organs of the body like the alimentary canal, reproductive tract etc. So they are known as visceral muscles.

Question 6.
Name the connective tissue layer of muscle bundles.
Answer:
Fascia.

Question 7.
Where is ciliary movement mostly seen in our body?
Answer:
Ciliary movement occurs in most of our internal tubular organ which are lined by ciliated epithelium.

Question 8.
Name the three types of muscles in humans.
Answer:
Skeletal, visceral and cardiac.

Question 9.
Name the cells which exhibit amoeboid movement.
Answer:
Macrophages and leucocytes in blood.

Question 10.
What are myofibrils?
Answer:
Large number of parallelly arranged filaments in the sarcoplasm are called myofibrils.

Question 11.
What is the striated appearance of myofibrils due to?
Answer:
Striated appearance of myofibril is due to the distribution pattern of two proteins, actin and myosin.

Question 12.
Name the functional Unit of muscles.
Answer:
Sacromere.

Question 13.
How are action and myosin filaments arranged during the resting state of muscle?
Answer:
In a resting state, the edges of the thin filaments on either side of the thick filaments, partially overlap the free ends of the thick filaments.

Question 14.
What is a H – zone?
Answer:
Central part of the A- band not overlapped by the thin filaments is called H – zone.

Question 15.
Name the protein which is distributed at regular intervals on the tropomyosin.
Answer:
Troponin.

Question 16.
What is the function of troponin?
Answer:
In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments

Question 17.
Name the monomers of myosin filament.
Answer:
Meromyosins.

Question 18.
What are the two parts of meromyosins?
Answer:
Meromyosin contains two parts:

• Globular head with a short arm called heavy meromyosin (HMM)
• A tail called Light meromyosin (LMM)

Question 19.
What is a cross arm?
Answer:
The head of meromyosin projects outwards at regular distance and angle from each other from the surface of polymerised myosin filament which is known as cross arm.

Question 20.
What causes fatigue in muscles?
Answer:
Repeated activation of the muscles lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen causing fatigue.

Question 21.
What Is myoglobin?
Answer:
Myoglobin is a red coloured oxygen storing pigment present in muscles.

Question 22.
Name two specialised connective tissues.
Answer:
Bone and cartilage

Question 23.
How many bones does a human being contain ?
Answer:
206 bones.

Question 24.
What salts are present In cartilage?
Answer:
Chondroitin salts.

Question 25.
How many bones does axial skeleton comprise of?
Answer:
80 bones.

Question 26.
What constitute axial skeleton?
Answer:
Skull, vertebral column, sternum and ribs.

Question 27.
Name the two set of bones in the skull.
Answer:
Cranial bones and facial bones.

Question 28.
What are ear ossicles made of?
Answer:
Malleus, Incus and Stapes.

Question 29.
How does skull region articulate with the superior region of the vertebral column?
Answer:
With the help of occipital condyles.

Question 30.
What is vertebral column formed of?
Answer:
Vertebral column is formed by 26 serially arranged units called vertebrae.

Question 31.
What is sternum?
Answer:
Sternum is a flat bone on the ventral midline of thorax.

Question 32.
What is a hyoid?
Answer:
Hyoid is a U- shaped bone present at the base of the buccal cavity.

Question 33.
Why are ribs called bicephalic?
Answer:
Ribs contain two articulation surface on its dorsal end and hence called bicephalic.

Question 34.
Name the major components of appendicular skeleton.
Answer:
The bones of the limbs and their girdles.

Question 35.
Name the longest bone in human body. (All India 2005)
Answer:
Femur (thigh bone)

Question 36.
What is acromion?
Answer:
The dorsal, flat, triangular body of scapula has a spine which projects as a flat, expanded process called the acromion.

Question 37.
What bones help In the articulation of the upper and the lower limbs with the axial skeleton.
Answer:
Pectoral and Pelvic girdle respectively.

Question 38.
What is the technical term for collar bone?
Answer:
Clavicle.

Question 39.
Name the cavity in the pectoral girdle with which head of humerus articulates.
Answer:
Glenoid cavity.

Question 40.
What Is meant by coxal bones?
Answer:
The two halves of the pelvic girdle are called coxal bones.

Question 41.
What is acetabulum in the pelvic girdle?
Answer:
Acetabulum is a cavity at the point of fusion of coxal bones to which the thigh bone articulates.

Question 42.
Name the components of coxal bone.
Answer:
Illium, ischium and pubis.

Question 43.
What are the Joints?
Answer:
Joints are points of contact between bones, or between bones and cartilages.

Question 44.
Name the classification of joints.
Answer:
Fibrous, cartilaginous and synovial.

Question 45.
What are pubic symphysis?
Answer:
Public symphysis is the cartilaginous joint between the two halves of the pelvic girdle on the ventral side.

Question 46.
Which type of joint Is the knee joint?
Answer:
Hinge joint.

Question 47.
How are synovial joints characterised ?
Answer:
Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones.

Question 48.
What type of Joint is present between carpal and metacarpal of thumb ?
Answer:
Saddle joint.

Question 49.
What causes gouty arthritis In human ? (All India 2005)
Answer:
lnflammation of joints due to accumulation of uric acid crystals.

1st PUC Biology Locomotion and Movement Two Marks Questions

Question 1.
Mention four special properties of muscles.
Answer:

• Contractility
• Excitability
• Extensibility
• Elasticity

Question 2.
Give two examples of ciliary movement in our body.
Answer:

• The coordinated movements of cilia in the trachea help in removal of dust particles and foreign substances inhaled along with atmospheric air.
• Passage of ova through the female reproductive tract is also facilitated by the ciliary movement.

Question 3.
Differentiate between striated and smooth muscles.
Answer:

Striated	Smooth
(i) These are found attached to the skeletal elements	(i) They are found in the wall of visceral organs.
(ii) Striations are prominent	(ii) Striations are absent
(iii) They are voluntary in functions.	(iii) They are involuntary in function
(iv) Cells are multinucleate	(iv) Cells are uninucleate
(v) They are innervated by voluntary nervous system.	(v) They are innervated by autonomic nervous system

Question 4.
Bring out the differences between cardiac muscles and smooth muscles.
Answer:

Cardiac	Smooth
(i)  They are found only in the wall of the heart. (ii)   Striations are faintly seen (iii)  Cells are cyclindrical and branched (iv)  Intercalated discs are present	(i) They are found in the wall of visceral organs. (ii) Striations are absent (iii) Cells are spindle shaped (iv)  Intercalated discs are absent

Question 5.
What is sarcoplasmic reticulum? What is its function?
Answer:
The endoplasmic reticulum of striated muscle fibres is called sarcoplasmic reticulum. It is the storehouse of calcium ions.

Question 6.
What are A-band and I-band?
Answer:
Each myofibril has alternate dark and light bands on it. The striated appearance of myofibril is due to the distribution pattern of two important proteins – Actin and myosin. The light bands contain actin and is called I-band on isotropic band, whereas the dark band called ‘A1 band or Anisotropic band contains myosin.

Question 7.
Differentiate between bone and cartilage.
Answer:

Bone	Cartilage
(i) It is a hard or rigid connective tissue. (ii) The matrix is deposited with calcium salts. (iii) One osteocyte is found in a lacuna. (iv) Haversian system are present.	(i) It is a semi-rigid connective tissue (ii) The matrix contains chondroitin salts. (iii) 2 to 4 chondrocytes are present in lacuna. (iv) Haversian systems are absent.

Question 8.
What are the two principal divisions of human skeletal system ? How many bones are present in each of them and what do they constitute of ?
Answer:
(i) Axial skeleton

• 80 bones
• constitute of skull, vertebral column,
• sternum and ribs.

(ii) Appendicular skeleton

• 126 bones
• Constitute of bones of the limbs and their girdles.

Question 9.
What are the functions performed by vertebral column ?
Answer:

• It protects the spinal cord;
• It supports the head.
• It serves as the point of attachment for the ribs.
• Provides place for attachment of muscles of the back

Question 10.
Describe the vertebra chondral ribs.
Answer:
The 8th, 9th and 10th pairs of ribs are called vertebra – chondral ribs.
They remain attached dorsally to the respective thoracic vertebrae and ventrally to the sternum through the seventh rib.

Question 11.
Name the bones of palm. How many of them are present in each palm?
Answer:
Bones of palm are called metacarpals. There are five of them in each palm.

Question 12.
Explain a synovial joint Give two examples.
Answer:
Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones. Such an arrangement allows considerable movement. These joints help in locomotion and many other movements. Ex: Ball and socket joint, Pivot joint.

Question 13.
Why can red muscle fibres work for a prolonged period, while a white muscle fibre suffers from fatigue soon? (Delhi 2005 C)
Answer:
Red muscle fibres contain a pigment myoglobin which stores oxygen. These muscles also contain plenty of mitochondria which can utilise the large amount of oxygen stored in them for ATP production. Hence they can work for a prolonged period without getting fatigue.

Whereas, white muscle fibres possess very less quantity of myoglobin and very few mitochondria in them. Hence they depend on anaerobic process for energy and get fatigue soon.

Question 14.
What is the role of calcium ions In muscle contraction ? (All India 2004)
Answer:

• Calcium ions bind to specific sites on the troponin component of thin (actin) filaments.
• As a result, conformational change occurs in the troponin molecules and the active sites of F- actin are exposed. These are the sites Specific to myosin head that shows Mg dependent ATP- ase activity.
• When calcium ions are pumped back into the sarcoplasmic reticulum, the troponin component becomes free to mask the active sites for myosin head. This leads to breakage of cross bridges and the actin filaments slide out of A – band.

Question 15.
List any four functions of skeleton in higher animals. (Delhi 1999)
Answer:

• It plays a vital role in movement and locomotion.
• It provides protection to many vital organs.
• It series as reservoir of calcium and phosphates.
• The bone marrow of long bones produces blood cells.

1st PUC Biology Locomotion and Movement Three Marks Questions

Question 1.
Explain giving one example of each, the three types of joints In human skeletons based on the capacity of movement. (Delhi 2006)
Answer:
(i) Immovable / Fibrous joint
The articulating bones are very tightly held with the help of white fibrous connective tissue and there is no space between the bones. Eg: Surtures between skull bones.

(ii) Slightly movable / Cartilaginous joints: The bones involved are joined together with the help of cartilages and allows limited movement. Eg: Joint between adjacent vertebrae in the vertebral column

(iii) Freely movable/synovial joints:
These joints are characterised by the presence of fluid filled synovial cavity between the articulating surfaces of two bones which allows considerable movement. Eg: Ball and socket joint, pivot joint etc.

Question 2.
What are the three types of muscle tissue? Write two characteristic points about the structure of each of them?
Answer:
Three types of muscle tissue are:
(a) Striated muscles

• These are skeletal muscles and are closely associated with the skeletal components of the body.
• Their activities are under the voluntary control of the nervous system.
• They are involved in locomotory actions and changes of body postures.

(b) Visceral muscles:

• They are located in the inner walls of hollow visceral organs like alimentary canal, reproductive tract etc.
• They do not exhibit any striation and are smooth if appearance.
• Their activities are not under the voluntary control of the nervous system.

(c) Cardiac muscles:

• They are the muscles of the heart and are striated.
• Cardiac muscle cells assemble in a branching pattern to form a cardiac muscle.
• They are involuntary in nature.

Question 3.
How many vertebrae In all, do we have? Categorize them on the basis of their location giving the specific number in each category. (Foreign 2004)
Answer:
We have a total of 26 vertebrae in our body.

• Cervical vertebrae (7) in the neck region.
• Thoracic vertebrae (12) present in the thoracic region of the trunk.
• Lumbar vertebrae (5) present in the abdominal region.
• Sacrum (1) is the triangular bone at the end of vertebral column.
  Coccygeal (1) which is vestigial tail bone in human being.

Question 4.
Describe the structure of sarcomere.
Answer:
The portion of the myofibril between two successive ‘z’ lines is called as sarcomere. It is the functional unit of muscle contraction. A sarcomere consists of a dark band in the centre and light bands on either side. The dark band or Anisotropic band (A band) is made of myosin and the light band on Isotropic band (I- band) is made of actin filaments.

Along the centre of the I- band is an elastic fibre called z – line, that bisects the band. Their filaments are attached firmly to the z – line. The myosin filaments are also held together in the centre by a thin fibrous membrane called M – Line. The central part of A band, not over lapped by thin filaments (I- band) is called a H – zone.

Question 5.
Draw a labelled diagram of vertebral column showing different regions.
Answer:

Question 6.
Name the different bones of forelimb and their number in human beings.
Answer:

• Humerus (1)
• Ulna (1)
• Radius (1)
• Carpals (8)
• Metacarpals (5)
• Phalanges (14)

Question 7.
Draw a neat labelled diagram of forelimb indicating all the bones.
Answer:

Question 8.
Name the A different bones of hind limb and their number in human beings.
Answer:

• Femur (1)
• Tibia (1)
• Fibula (1)
• PateNa (1)
• Tarsals (7)
• Metatarsals (5)
• Phalanges (14)

Question 9.
Draw a neat labelled diagram of hind limb indicating ail the bones.
Answer:

1st PUC Biology Locomotion and Movement Five Marks Questions

Question 1.
Explain the sliding filament theory of the mechanism of muscle contraction.
Answer:

Mechanism of muscle contraction is best explained by the sliding filament theory which states that contraction of a muscle fiber takes place by the sliding of the thin filaments over the thick filaments.

‘Muscle Contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. A motor neuron along with the muscle fibres connected to it constitute a motor unit. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor – end plate. A neural signal reaching this junction releases a neurotransmitter which generates an action potential in the sacrolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.

Increase in Ca⁺⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin filaments towards the centre of ‘A’ band. The Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e contraction. During contraction the T bands get reduced, whereas the ‘A’ bands retain the length.

The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic Cisternae resulting in the masking of actin filaments. This causes the return of Z lines back to their original position, i.e. relaxation.

Question 2.
Briefly give an account of any five disorders of muscular and skeletal system.
Answer:

• Myasthenia gravis: Auto immune disorder affecting neuro muscular junction leading to fatigue, weakening and paralysis of skeletal muscles.
• Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.
• Tetany : Rapid spasms in muscle due to low calcium ions in body fluid.
• Gouty arthritis: Inflammation of joints due to accumulation of uric acid crystals.
• Osteo porosis: Age related disorder characterised by decreasedbdhMfiass and increased chances of fractures. Decreased levels of estrogen is a common cause.

Question 3.
Represent diagrammatically the stages in cross bridge formation, rotation of head and its
Answer:

Question 4.
Draw a neat diagram of human skull labelling any 10 parts.
Answer:

Question 5.
Name different type of synovial Joint giving one example of each type.
Answer:

• Ball and Socket joint. Eg: between humerus and pectoral girdle.
• Hinge joint. Eg: Knee joint and Elbow joint.
• Pivot joint. Eg: between atlas and axis
• Gliding joint. Eg: between the carpals
• Saddle joint Eg: between carpal and metacarpal of thumb.

Question 6.
Draw a neat labelled diagram of
(a) An actin filament
(b) Myosin
Answer:

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Karnataka 1st PUC Chemistry Question Bank Chapter 13 Hydrocarbons

1st PUC Chemistry Hydrocarbons One Mark Questions and Answers

Question 1.
What are hydrocarbons ?
Answer:
Organic compounds containing only carbon and hydrogen are called hydrocarbons.

Question 2.
What are alkanes ?
Answer:
Alkanes are saturated aliphatic hydrocarbons containing carbon to carbon single bonds.

Question 3.
Give the general formula of alkanes.
Answer:
The general formula of alkanes is C_nH_2n+2

Question 4.
What are saturated hydrocarbons ?
Answer:
The hydrocarbons containing only carbon – carbon single bonds saturated hydrocarbons.

Question 5.
What is the order of reactivity of halogens towards alkanes.
Answer:
The reactivity of halogens towards alkanes varies as Flourine > Chlorine > Bromine > Iodine i.e., F > Cl > Br > I.

Question 6.
Why alkanes are called parafins ?
Answer:
Because of low reactivity.

Question 7.
What is the nature ofC-C bond in alkanes?
Answer:
These are sigma (σ) bonds.

Question 8.
What type of structural isomerism is shown by alkanes?
Answer:
Chain Isomerism.

Question 9.
What is Photochemical reaction ?
Answer:
Reaction carried in the presence of light.

Question 10.
Which class of organic compounds are potential carcinogen?
Answer:
Polynuclear aromatic hydrocarbons.

Question 11.
What is huckel Rule ?
Answer:
It states that a compound is said to be aromatic. If it has (4n +2) p electrons which are de-localised where n = 0,1, 2, 3, ………

Question 12.
Name the scientist who first isolated benzene.
Answer:
Faraday isolated benzene in 1825.

Question 14.
What is decarboxylation ?
Answer:
The process of removing carbon dioxide from sodium salts of acid with the help of soda lime.

Question 15.
What is electrophilic subsitution reaction ?
Answer:
Those reaction in which weaker electrophile is replaced by stronger electrophile are called electrophilic substitution reaction.

Question 16.
Why is addition reaction of bromine to benzene difficult?
Answer:
Due to delocalisation of π electrons. It does not have pure double bond.

Question 17.
What are arenas? Give general formula of Monocyclic arenas.
Answer:
Arenes are aromatic hydrocarbons. General formula of arenas is C_nH_2n-6

Question 18.
What are unsaturated hydrocarbons?
Answer:
The hydrocarbons which contain atleast one carbon to carbon double bond or triple bond are called unsaturated hydrocarbons.

Question 19.
What type of isomerism is shown by alkenes ?
Answer:
Chain isomerism.

Question 20.
What are alkenes ?
Answer:
Alkenes are unsaturated aliphatic hydrocarbons containing one carbon to carbon double bond.

Question 21.
Give the general formula of alkenes.
Answer:
The general formula of alkenes is C_nH_2n.

Question 21.
Why are alkenes and alkenes called unsaturated hydrocarbons?
Answer:
Due to presence of C = C & C ≡ C bonds respectively.

Question 22.
What is the state of hybridisation of carbon atoms in alkenes ?
Answer:
Sp²

Question 23.
A compound decolourise yellow colour of bromine. What does it show ?
Answer:
It is unsaturated in nature.

Question 24.
What is Lindlar’s catalyst ?
Answer:
Palladium supported over calcium carbonate and deactivated with quinoline is called Lindlar’s Catalyst.

Question 25.
Name the hydrocarbon which contains acidic hydrogen.
Answer:
Ethylene (HC ≡ CH).

Question 26.
Give one hydrocarbon which delcolourises alk KMnO₄.
Answer:
Ethene (CH₂ = CH₂)

Question 27.
Name the reagent which brings about dehydrohalogination.
Answer:
Alcoholic potash.

Question 28.
What is the major product formed when propene reacts with hydrogen bromide ?
Answer:
2 – bromopropane.

Question 29.
Name the product formed when HBr reacts with 2 – methyl propene.
Answer:

Question 30.
What are alkynes?
Answer:
Alkynes are unsaturated aliphatic hydrocarbons containing one carbon to carbon triple bond.

Question 31.
Give the general formula of alkynes.
Answer:
The general formula of alkynes is C_nH_2n-2

Question 32.
What is the hybridisation of carbon atoms in acetylene ?
Answer:
sp

Question 33.
What is a vicinal dihalide ?
Answer:
A compound with halogen atoms on adjacent carbon atom.

Question 34. Give the example of vicinal dihalide.
Answer:

Question 35.
Give an example of geminal dihalide.
Answer:
CH₃ – CHCl₂ (1,1 – dichlorethane)

Question 36.
Give an example of alkyne.
Answer:
Acetylene CH ≡ CH

Question 37.
Why are alkenes called olefins ?
Answer:
Because they are oily forming compounds i.e., most of the oils are unsaturated.

Question 38.
Give an addition reaction of alkynes.
Answer:
CH ≡ CH + HBr → CH₂ ≡ CH – Br (Vinyl Bromide)

Question 39.
Give the resonance structures of benzene.
Answer:

Question 40.
Name the electrophiles in the following reactions

1. Chlorination
2. Nitration
3. Sulphonation
4. Friedel Craft’s methylation

Answer:

1. Chlorination – Cl⁺
2. Nitration – \(\mathrm{NO}_{2}^{+}\)
3. Sulphonation – SO₃ .
4. Friedel Crafts methylation – \(\mathrm{CH}_{3}^{+}\)

Question 41.
Write the Geometrical isomers of CHBr = CHBr
Answer:

Question 42.
Which catalyst is most effective even in the polymerization of ethane to polythene ?
Answer:
Ziegler – Nata Catalyst

Question 43.
What is the compostion of Zeigler Natta Catalyst?
Answer:
Triethylaluminium and titanium tetracholride inert solvent.

Question 44.
Name one Carcinogenic compound.
Answer:
Anthracene of Benzanthracene.

Question 45.
What is the number of a and n bonds in N ≡ C-CH = CH- C ≡ N?
Answer:
There are 7 σ bonds and 5 π bonds.

Question 46.
Name the compound formed when heptane is subjected to aromatisation.
Answer:
Toulene.

Question 47.
What is the cause of Geometrical Isomerism ?
Answer:
The restricted rotation around carbon to carbon double bond

Question 48.
What is cracking of hydrocarbon ?
Answer:
Cracking is a process of breaking higher hydrocarbons by heating.

Question 49.
What is the trade name of Benzene Hexacarbon ?
Answer:
Gammaxane.

1st PUC Chemistry Hydrocarbons Two Marks Questions and Answers

Question 1.
What is the action of ethane with bromine in carbon tetra chloride?
Answer:
Ethene reacts with bromine in carbon tetrachloride to give 1, 2 – dibromethane. Orange colour of bromine is discharged.

Question 2.
What is the action of hydrogen halide on alkene?
Answer:
Alkene reacts with hydrogen halide to form alkyl halide. The addition is governed by Markownikoff’s rule.

Question 3.
How do you obtain an alkene from alkyne ?
Answer:
Alkynes react with hydrogen in the presence of (Palladium supported over calcium carbonate and deactivated with quinoline) Lindlar’s catalyst, to give alkene.

Question 4.
How do you convert ethene to ethane?
Answer:
When a mixture of ethene and hydrogen is passed over heated nickel catalyst at 200°C, ethane is obtained.
\(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}_{2}+\mathrm{H}_{2} \frac{\mathrm{Ni}}{200^{\circ} \mathrm{C}} \mathrm{CH}_{3}-\mathrm{CH}_{3}\)

Question 5.
How is propene obtained from propyl chloride ?
Answer:
When propyl chloride is heated with alcoholic potash propene is obtained.
\(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2} \mathrm{Cl}+\mathrm{KOH}_{(\mathrm{alc})} \stackrel{\Delta}{\longrightarrow} \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}_{2}+\mathrm{KCl}+\mathrm{H}_{2} \mathrm{O}\).

Question 6.
What is Wurtz reaction ? Give example.
Answer:
When alkyl halides are heated with sodium metal in ether medium higher alkanes are formed. This reaction is known as Wurtz reaction and employed for the synthesis of higher alkanes containing even number of carbon atoms.

Question 7.
How is Methane prepared from sodium acetate ?
Answer:
Decarboxylation : When sodium salt of carboxylic acid is heated with soda lime (mixture of sodium hydroxide and calcium oxide), an alkane containing one carbon atom less than parent carboxylic acid is formed. This reaction is called decarboxylation.

Question 8.
How is alkane prepared from Kolbe’s electrolytic method ?
Answer:
A concentrated sodium salt of a carboxylic acid is electrolysed. The alkane is formed at the anode as one of the products. This process is called Kolb’e electrolysis.

Question 9.
What is Pyrolysis ? Give example.
Answer:
The decomposition of higher alkane into a mixture of lower alkanes, alkenes, etc by the application of heat is called pyrolysis or cracking.

Question 10.
What is Aromatisation ? Give example.
Answer:
Hexane or higher akanes when heated in presence of vanadium pentoxide (V₂O₅), molybdenium oxide (MO₂O₃) or chromium oxide (Cr₂O₃) supported on alumina (Al₂O₃) at 800 K and 10-20 atm pressure give benzene or its alkyl derivatives with the liberation of hydrogen. This dehydrogenation process which involves cyclis^ion of alkanes is known as aromatization.

Question 11.
What is isomerisation ? Give example.
Answer:
When unbrached alkanes are heated with anhydrous aluminium chloride and hydrogen chloride, isomeric branched alkanes are formed. This process is called isomerisation.

Question 12.
What is Geometrical isomerism ?
Answer:
Compounds having same molecular formula and structural formula but differ in the spatial arrangement of atoms or group of atoms due to restricted rotation of carbon carbon double bond.

Question 13.
What are the conditions for Geometrical isomerism ?
Answer:

• The molecule should contain double bond.
• Each carbon atom joined by the double bond, must be attached to two different groups.

Question 14.
What is Ozonalysis ? Give example.
Answer:
The ozonolysis of alkenes involves addition of ozone molecule to carbon-carbon double bond of alkenes to form ozonide. This follows hydrolysis of the ozonoide by H₂O/Zn to yield corresponding aldehydes and / or ketones. The addition of ozone to alkene followed by hydrolysis is known as ozonolysis.

Question 15.
How is ethene prepared ?
Answer:
When 1, 2 – dihaloalkanes (vicinal dihalides) are heated with zinc metal in presence of methanol corresponding alkenes are formed. This reaction is called dehalogenation.
\(\mathrm{Br}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{Br}+\mathrm{Zn} \frac{\mathrm{CH}_{3} \mathrm{OH}}{\text { heat }} \mathrm{CH}_{2}=\mathrm{CH}_{2}+\mathrm{ZnBr}_{2}\)

Question 16.
What are the uses of LDPE and HDPE ?
Answer:
LDPE is used for

• making transparent films for packaging garments and food,
• as an insultor.

HDPE is used for

• making crates and large boxes
• production of carry bags, containers, house hold articles and toys.

Question 17.
What happens when Ammonical solution of silver Nitrate treated with Acetylene ?
Answer:
Acetylene when passed through an ammonical solution of silver nitrate (Toallen’s reagent) white solid of silver acetylide is separated.

Question 18.
Give four examples for isomerism in Arenes.
Answer:

Question 19.
Give three examples for fused polycyclic arene
Answer:

Question 20.
State Markownkoff s rule.
Answer: When an unsymmetrical molecule adds to an unsymmetrical alkene, the negative part of the adding molecule adds to the carbon atom involved in the double bond, containing the least number of hydrogen atoms. Thus according to Markonwkoff’s rule the addition takes place as follows :

1st PUC Chemistry Hydrocarbons Four/Five Mark Questions and Answers

Question 1.
Explain the action of chlorine on methane in the presence of sunlight.
Answer:
Methane reacts with chlorine in the presence of diffused sunlight to give methyl chloride, methylene chloride, chloroform and carbon tetrachloride.

Question 2.
Explain the mechanism of chlorination of methane, according to Free Radical.
Answer:
Mechanism of chlorination of methane involves three types.
1. Initiation : Chlorine absorbs energy and undergoes homolysis to give chlorine free radicals.
\(\mathrm{Cl}-\mathrm{Cl} \stackrel{\mathrm{hy}}{\longrightarrow} 2 \mathrm{Cl}^{\bullet}\)

Step 2 : Propagation : Chlorine free radical reacts with methane to give methyl free radical.
\(\mathrm{Cl}^{\bullet}+\mathrm{CH}_{4} \longrightarrow \mathrm{CH}_{3}^{\bullet}+\mathrm{HCl}\)
The methyl free radical reacts with chlorine to form methyl chloride and chlorine free radical.

Step 3 : Termination : Free radials combine to form stable products.

Question 3.
Explain the mechanism of addition of hydrogen bromide to propene.
Answer:
The mechanism of addition of hydrogen bromide to propene takes place in three steps. Step 1: Hydrogen bromide dissociates into H⁺ and Br-
H-Br → H⁺+Br^–

Step 2 : The electrophile H+ attacks propene to form carbocation.

of the two carbocations (I) and (II), carbocations (I) is more stable and is formed more readily.

Step 3 : The nucleophile Br attacks the carbocation (I) to give 2 – bromopropane.

Question 4.
How is the manufacture of LDPE & HDPE ?
Answer:
Low density polythene is manufactured by compressing ethane under very high pressure (1500-2000 atmospheres) at about 475 K in the presence of a small amount of oxygen as catalyst.

High density polythene is obtained by passing ethene under pressure of 6 atmospheres at about 340 K into heptane, an inert solvent containing Zielgler-Natta catalyst (triethyl) aluminium and titanium tetrachloride)

Question 5.
Give four uses of aceylene.
Answer:

1. Oxyacetylene flame is used for cutting and welding of metals.
2. Acetylene and its derivatives are widely used in synthetic organic chemistry for synthesis of cis and trans-alkenes, methyl ketones, etc.
3. Acetylene is used as illuminant in hawker’s lamp and in light houses.
4. Acetylene is used for ripening of fruits and vegetables.
5. Acetylene is used for manufacture of ethyl alcohol, acetaldehyde, acetic acid, vinyl plastics, synthetic rubbers such as Buna-N and synthetic fibres such as Orlan.

Question 6.
Give 4 uses of ethene.
Answer:

1. Lower members of the family are used as fuels and illuminants.
2. Alkenes and substituted alkenes upon polymerization form a number of useful polymers such as polythene, PVC, Teflon, orlon, etc.,
3. Ethene is employed for preparation of ethyl alcohol and ethylene glycol (anti-freeze).
4. Ethylene is used for artificial ripening of green fruits.
5. Ethylene also used in oxygen-ethylene flame for cutting and welding of metals.

Question 7.
Give four uses of methane.
Answer:

1. Methane in the form of natural gas (CNG) is used for running scooters, cars, buses, etc., LPG (Mixture of butane and isobutene) is used as a fuel in homes as well as in industry.
2. Methane is used to make carbon black which is used in the manufacture of printing inks, paints and automobile tyres.
3. Cataltic oxidation of alkanes gives alcohols, aldehydes an carboxylic acids.
4. Higher alkanes in form of gasoline, kerosene oil, diesel, lubricating oils and paraffin wax are widely used.
5. Methane is used for manufacture halogen containing compounds such as CH₂Cl₂ , CHCl₃ , CCl₄ etc. which are used as solvents both in laboratory and industry.

Question 8.
Give the structural elucidation of benzene.
Answer:
1. From elemental analysis and molecular mass determination, the molecular formula of benzene is found to be C₆H₆.

2. On the basis of molecular formula benzene is highly unsaturated compound.

3. Benzene does not show alkene properties. Benzene is quite stable. It does not decolourise cold aqueous solution of potassium paramanganate.

4. Benzene shows cyclic structure,
(a) Benzene contains three double bonds. Benzene adds three moles of hydrogen in presence of nickel catalyst to form cyclohexane.

\(\mathrm{C}_{6} \mathrm{H}_{6}+3 \mathrm{H}_{2} \frac{180^{\circ} \mathrm{C}}{\mathrm{Ni}} \mathrm{C}_{6} \mathrm{H}_{12}\)

(b) All the six hydrogen atoms in benzene are identical – benzene reacts with bromine in presence of FeBr3 catalyst to form monobromobenzene.

\(\mathrm{C}_{6} \mathrm{H}_{6}+\mathrm{Br}_{2} \stackrel{\mathrm{FeBr}_{3}}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Br}+\mathrm{HBr}\)

5. Kekule proposed benzene is a planar ring structure with alternate single and double bonds.

6. To overcome this drawback, Kekule suggested that benzene is a mixture of two forms, which are in rapid oscillation.

7. It is found that the bond length in benzene is same for all C-C bonds (0.139 nm). This lies between C-C single bond (0.154 nm) and C-C double bond length (0.134 nm).

8. Resonance structure: Resonance hybrid is more stable than structure 1 and 2. The stability of benzene due to resonance is so great that n bonds of the molecule will normally resist breaking. This explain the stability of benzene.

Question 9.
Explain the mechanism of halogenation or chlorination of benzene.
Answer:
Halogenation: Benzene reacts with chlorine in the presence of FeCl₃ or AlCl₃ to form chlorobenzene.

Machanism : This involves the following steps.

Step 1: Generation of eiectrohile Cl – Cl + FeCl₃ → Cl⁺ + \(\mathrm{FeCl}_{4}^{-}\)
Step 2 : The electrophile Cl⁺ attacks benzene ring to form a carbon cation which is resonance stabilised.

Step 3 : Loss of a proton to give chlorobenzene. The proton is removed by FeCU.

Question 10.
Explain the mechanism of nitration of benzene.
Answer:
Nitration benzene reacts with a mixture of concentrated nitric acid and concentrated sulphuric acid at 50°C to form nitrobenzene.

Mechanism : This involves the following steps.
Step 1: Generation of electrophile nitronium ion \(\mathrm{NO}_{2}^{+}\)
\(\mathrm{HNO}_{3}+2 \mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{NO}_{2}^{+}+\mathrm{H}_{3} \mathrm{O}^{+}+2 \mathrm{HSO}_{4}^{-}\)

Step 2 : The electrophile NO₂ attacks the benzene ring to form a carbocation which is resonance stabilized.

Step 3 : Loss of a proton to give nitrobenzene. The proton is removed by \(\mathrm{HSO}_{4}^{-}\)

Question 11.
Explain the mechanism of sulphonation of benzene?
Answer:
Sulphonation : Benzene reacts with concentrated sulphuric acid at 80°C to form benzene sulphoric acid.

Mechanism : This involves the following steps.

Step 1: Generation of electrophile SO₃.
\(2 \mathrm{H}_{2} \mathrm{SO}_{4} \rightleftharpoons \mathrm{SO}_{3}+\mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{HSO}_{4}^{-}\)

Step 2 : The electrophile SO₃ attacks the benzene ring to form a carbocation

Step 3: Loss of a proton to from a sulphonate ion. The proton is removed by \(\mathrm{HSO}_{4}^{-}\)

Step 4 : Addition of proton to give benzene sulphonic acid.

Question 12.
Explain the mechanism of Friedel craft alkylation of benzene.
Answer:
Friedel – Craft alkylation reaction Benzene reacts with methyl chloride in presence of anhydrous aluminium chloride to form toluene. This is called Friedel-Crafts alkylation reaction.

The mechanism of Friedel Craft’s alkylation reaction involves the following steps: