1st PUC Biology Question Bank Chapter 14 Respiration in Plants

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Karnataka 1st PUC Biology Question Bank Chapter 14 Respiration in Plants

1st PUC Biology Respiration in Plants NCERT Text Book Questions and Answers

Question 1.
Differentiate between
(a) Respiration and Combustion
Answer:

Respiration	Combustion
(1) It is a biochemical process	It is a physicochemical process
(2) It occurs in living cells	It does not occur in living cells
(3) ATP is generated	ATP is not generated
(4) Enzymes are required	Enzymes are not required
(5) It is a biologically controlled process	It is an uncontrolled process

(b) Glycolysis and Krebs’ cycle
Answer:

Glycolysis	Krebs’ cycle
(1) It is a linear pathway	It is a cyclic pathway
(2) It occurs in cell cytoplasm	It occurs in mitochondrial matrix
(3) It occurs in both aerobic and anaerobic respiration	It occurs in aerobic respiration
(4) It generates 2 NADH2 and 2 ATP molecules on break down of one glucose molecules	It produces 6 NADH2, 2FADH2 and 2 ATP molecules on break down of two acetyl-CoA molecules.

(c) Aerobic respiration and Fermentation
Answer:

Aerobic respiration	Fermentation
(1) Oxygen is used for deriving energy	Fermentation occurs in the absence of oxygen but presence of microbes
(2) Occurs in the cytoplasm and mitochondria	Occurs in the cytoplasm
(3) End products are carbon dioxide and water	End products are ethyl alcohol and carbon dioxide
(4) Complete oxidation the respiratory substrate takes place	Incomplete oxidation of the respiratory substrate takes place
(5) About 36 ATP are produced	Only 2 ATP molecules are produced

Question 2.
What are respiratory substrates? Name the most common respiratory substrate.
Answer:
The compounds that are oxidised during the process of respiration process are known as respiratory substrates. Usually carbohydrates are oxidised to release energy, but proteins, fats and even organic acids can be used as respiratory substrates in some plants, under certain conditions.

Question 3.
Give the schematic representation of glycolysis?
Answer:

Question 4.
What are the main steps in aerobic respiration? Where does it take place?
Answer:
The major steps in aerobic respiration and the sites where they occur are listed in the given table.

Step	Site of Occurrence
(1) Glycolysis	cytoplasm
(2) Krebs cycle	matrix of mitochondria
(3) electron transport system	Inner mitochondrial membrane
(4) oxidative phosphorylation	F0-F1 particles in the inner mitochondrial membrane.

Question 5.
Give the schematic representation of an overall view of Krebs’ cycle.
Answer:

Question 6.
Explain ETS
Answer:

Electron Transport System (ETS)

• ETS occurs in the electron transport particles (ETP) on the inner surface of the inner membrane of mitochondria.
• It is a metabolic pathway through which electron passes from one carrier to another.
• Electrons from NADH produced in the mitochondrial matrix during citric acid cycle are oxidised by an NADH dehydrogenase (complex I), and electrons are then transferred to ubiquinone located within the inner membrane.
• Ubiquinone also receives reducing equivalents via FADH₂ generated during the oxidation of succinate by succinate dehydrogenase (complex II).
• The reduced ubiquinone, called ubiquinol, is then oxidised by transfer of electrons to cytochrome c, cytochrome bc₁ – complex (complex III).
• Cytochrome c acts as a mobile carrier between complex III and complex IV.
• Complex IV refers to cytochrome c oxidase complex containing cytochromes a and a, and two copper centres.
• When the electrons are pass from one carrier to another carrier via complex I to IV in the electron transport chain, they are coupled to ATP synthase (complex V) for the formation of ATP from ADP and iP.
• Oxygen functions as the terminal acceptor of electrons and is reduced to water along with the hydrogen atoms. It drives whole process by removing hydrogen from system.
• In respiration, energy of oxidation-reduction utilised for the production of proton gradient. So the process is called as oxidative phosphorylation.
• Higher proton concentration in the outer chamber causes the protons to pass inwardly into matrix or inner chamber causes the protons to pass inwardly into matrix or inner chamber through the inner membrane.
• The energy of the proton gradient is used in attaching a phosphate radicle to ADP by high energy bond.
• Oxidation of one molecule of NADH₂ produces 3 ATP molecules while similar oxidation of FADH₂ forms 2 ATP molecules.
• ATP synthase (complex V) helps in ATP synthesis. It consists of two major components F₁ andF_o.
• F₁ (headpiece) is a peripheral membrane protein complex and contains the site for ATP synthesis while F_o is an integral membrane protein complex that forms a channel through which protons across the inner membrane.
• For each ATP produced, 2H⁺ passes through F_o from the intermembrane space to the matrix down the electrochemical proton gradient.

Question 7.
Distinguish between the following:
(a) Aerobic respiration and Anaerobic respiration
Answer:

Aerobic respiration	Anaerobic respiration
(1) It uses oxygen for deriving energy	it occurs in the absence of oxygen
(2) It occurs in the cytoplasm and mitochondria	It occurs in the cytoplasm
(3) The end products are carbon dioxide & water	The end products are ethyl alcohol and carbon dioxide
(4) Complete oxidation of the respiratory substrate takes place	Incomplete oxidation of the respiratory substrate takes place.
(5) 36-38 ATP molecules lire produced	only 2 ATP molecules are produced

(b) Glycolysis and Fermentation
Answer:

Glycolysis	Fermentation
(1) Glycolysis occurs during aerobic and anaerobic respiration	Fermentation is a type of anaerobic respiration
(2) Pyruvic acid is produced as its end product	Ethanol or lactic acid is produced as its end product.

(c) Glycolysis and Citric acid Cycle
Answer:

Glycolysis	Citric acid Cycle
(1) It is a linear pathway	It is a cyclic pathway
(2) It occurs in the cell cytoplasm	It occurs in the mitochondrial matrix
(3) It occurs in both aerobic & anaerobic respiration	It occurs in aerobic respiration
(4) one glucose molecule breaks down to generate 2 NADH2 & 2 ATP molecules	It produces 6 NADH, 2FADH2 and 2 ATP molecules on break­down of two acetyl- CoA molecules

Question 8.
What are the assumptions made during the calculation of net gain of ATP?
Answer:
The calculations of a net gain of ATP for every glucose molecule oxidised is made on certain assumptions that are as follows:

• There is a sequential, orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle, and ETS pathway following one after another.
• The NADH synthesized in glycolysis is transferred into the mitochondria and undergoes oxidative phosphorylation.

Question 9.
Discuss “The respiratory pathway is an amphibolic pathway.”
Answer:

1. Glucose is the favoured substrate for respiration. All carbohydrates are usually first converted into glucose before they are used for respiration.
2. Respiration involves breakdown as well as the synthesis of substrates, the respiratory process involves both catabolism and anabolism.
3. Glucose breakdown to release energy. This is called catabolism. Many compounds are also withdrawn from the respiratory pathway for the synthesis of new substrates (for example acetyl CoA is withdrawn from the pathway to synthesis fatty acids when needed).
4. This is called anabolism. Thus respiratory pathway involves both anabolism and catabolism So it is called an amphibolic pathway.

Question 10.
Define RQ. What Is Its value for fats?
Answer:
Respiratory quotient or respiratory ratio can be defined as the ratio of the volume of to of the volume of CO₂ liberated to the volume of the O₂ consumed, or; CO₂ evolved to the volume of O₂ consumed during respiration. The value of respiratory quotient depends on the type of respiratory substrate. Its value is one for carbohydrates. However, it is always less than one for fats as fats consume more oxygen for respiration than carbohydrates.

Question 11.
What is oxidative phosphorylation?
Answer:

1. Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate (ATP).
2. During oxidative phosphorylation, electrons are transferred from electrons donors to electron acceptors such as oxygen, in redox reactions.
3. These redox reactions release energy, which is used to form ATP.
4. In eukaryotes, these redox reactions are carried out by a series of five protein complexes within mitochondria.
5. When the electrons pass from one carrier to another via complex I to IV in the electron transport chain, they are coupled to ATP synthase (complex V) for the production of ATP from ADP and inorganic phosphate.
6. The number of ATP molecules synthesised depends on the nature of the electron donor. Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while that of one molecule of FADH2 produces 2 molecules of ATP.
   Oxygen acts as the final hydrogen acceptor.
7. Unlike photophosphorylation where it is the light energy that is utilised for the production of proton gradient required for phosphorylation, in respiration, it is the energy of oxidation-reduction utilised for the same process.
8. It is for this reason that the process is called oxidative phosphorylation.

Question 12.
What is the significance of the step-wise release of energy in respiration?
Answer:
The process of breathing is very much connected to the process of release of energy from food. Let us try and understand how this happens. All the energy required for ‘life’ processes is obtained by oxidation of some macromolecules mat we call ‘food’. Only green plants and cyanobacteria can prepare their own food; by the process of photosynthesis, they trap light energy and convert it into chemical energy that is stored in the bonds of carbohydrates: like glucose, sugar, and starch. We must remember that in green plants too, not all cells, tissues, and organs photosynthesize; only cells containing chloroplasts, which are most often located in the superficial layers, carry out photosynthesis. Hence, even in green plants all other organs, tissues, and cells that are non-green need food for oxidation.

Hence, food has to be translocated to all non-green parts. Animals are heterotropic i.e. they obtain food from plants directly (herbivores) or indirectly (carnivores). Saprophytes like fungi are dependent on dead and decaying matter.
Photosynthesis of course takes place within the chloroplasts (in the eukaryotes), whereas the breakdown of complex molecules to yield energy takes place in the cytoplasm, and in the mitochondria (also only in eukaryotes).

The breaking of the C-C bonds of complex compounds through oxidation within the cells, leading to the release of a considerable amount of energy is called respiration. The compounds that are oxidized during this process are known as respiratory substrates. Usually, hydrates are oxidized to release energy, but proteins, fats, and even organic acids can be used as respiratory substances in some plants under certain conditions.

During oxidation within a cell, all the energy contained in respiratory substrates a not released free into the cell, in a single step. It is released in a series of slow stepwise reactions controlled by enzymes and it is trapped as chemical energy in the form of ATP. Hence it is important to understand that the energy released by oxidation in respiration is not (or rather cannot be) used directly but is used to synthesize ATP, which is broken down whenever (and wherever) energy needs to be utilized.

Hence ATP acts as the energy currency of the cell. This energy trapped in ATP is utilized in various energy-requiring processes of the organisms, and the carbon skeleton produced during respiration is used as precursors for the biosynthesis of other molecules in the cell.

1st PUC Biology Respiration in Plants Additional Questions and Answers

1st PUC Biology Respiration in Plants One Mark Questions

Question 1.
Which organic compound acts as a link between glycolysis and Kreb’s cycle?
Answer:
Acetyl Co-A acts as a link between glycolysis and the Krebs cycle.

Question 2.
Name the scientist who was awarded Nobel Prize for the work on respiration. (Oct. 84)
Answer:
Sir Hans Krebs.

Question 3.
What term is given to the reduced ubiquinone?
Answer:
Ubiquinol is a reduced form of ubiquinone.

Question 4.
What is Fermentation? (Apr. 87, July 2006)
Answer:
Anaerobic respiration carried out by microorganisms.

Question 5.
How many ATP is formed at the end of Kreb’s cycle? (Mar. 89)
Answer:
38.

Question 6.
Name the site of glycolysis in a ceil. (Oct. 90, 92, July 2006, March 2011)
Answer:
Cytoplasm

Question 7.
Name the products of anaerobic respiration. (Apr. 94)
Answer:
Ethyl alcohol and carbon dioxide

Question 8.
Name the coenzyme associated with dehydrogenation of Succinic acid during Krebs cycle. (Apr. 96)
Answer:
NAD.

Question 9.
Name the cell organelle in which Racker’s particles are present. (Apr. 98,2005)
Answer:
Mitochondria

Question 10.
What happens to fatty acids before they form the respiratory substrates?
Answer:
Krebs’ cycle.

Question 11.
What is Pasteur effect ? (Apr. 99, 09, Oct. 02, June 2009)
Answer:
When the anaerobic yeast cells adapt to aerobic conditions in the presence of oxygen the outcome is termed Pasteur’s effect.

Question 12.
Define Respiratory quotient? (Oct. 99, 03, Apr. 2005, March 2010)
Answer:
The respiratory quotient is defined as the ratio of the volume of CO₂ liberated to the volume of the O₂ consumed, or;

Question 13.
Expand ATP. (Apr. 2000)
Answer:
Adenosine Tri Phosphate

Question 14.
Expand FAD. (Oct. 2000)
Answer:
Flavin Adenine Dinucleotide.

Question 15.
How many ATP molecules are obtained in the process of respiration?
Answer:
The two molecules obtained by the actions of aldolase from fructose -1,6-biphosphate are Glyceraldehyde 3-phosphate and Dihyroxy acetone-3-phosphate.

Question 16.
Give the chemical equation of aerobic respiration. (Apr. 2002)
Answer:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy.

Question 17.
How many NADH₂ molecules are resulted due to the degradation of one mole of pyruvic acid during Kreb’s Cycle? (Apr. 2003)
Answer:
4.

Question 18.
What are Aerobes?
Answer:
The organisms respire in the presence of O₂ are called aerobes.

Question 19.
Which is the site of Krebs cycle? (Apr. 07)
Answer:
Mitochondrial Matrix.

Question 20.
What are respiratory substrates?
Answer:
The substances present in cell protoplasm which undergo oxidation and generate energy are called respiratory substrates.

Question 21.
Name the three-carbon compound formed during glycolysis.
Answer:
Pyruvate

Question 22.
Name the site of the EMP pathway.
Answer:
Cytoplasm

Question 23.
What Is the RQ value for carbohydrates?
Answer:
One / unity (Apr. 2004)

Question 24.
Give reason: (July 2008)
RQ value of glucose is 1.
Answer:
It is because the volume of CO₂ evolved is equal to the volume of 02 absorbed.

Question 25.
Give reason: (March 2009)
RQ value of protein is generally less than one.
Answer:
Proteins are Compounds poor in oxygen and require more of external 02 for oxidation hence RQ is less than one.

1st PUC Biology Respiration in Plants Two Marks Questions

Question 1.
Draw a neat labelled diagram of mitochondria. (Oct. 97)
Answer:

Question 2.
Name any two respiratory substrates and their RQ values. (M.Q.P.)
Answer:
Respiratory substrates.
Carbohydrates with R.Q. = unity
Proteins with R.Q. = 0.7.

Question 3.
Define Aerobic Respiration. Write an equation. (April 99)
Answer:
Aerobic respiration is the complete oxidation of the respiratory substrate into carbon-di-oxide and water.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy

Question 4.
What is fermentation? Give 2 examples of products of fermentation. (Oct. 2000)
Answer:
Anaerobic respiration carried out by microorganisms is called fermentation. The products of fermentation are lactic acid, ethyl alcohol, and carbon dioxide.

Question 5.
List our any 2 difference between anaerobic respiration and fermentation. (April 2001)
Answer:
anaerobic respiration:
(1) It is a partial breakdown of the respiratory substrate into alcohol and

C₆H₁₂O₆ + 2C₂H₅OH+ 2C₂O + energy

(2) The end product of glycolysis is pyruvic acid which yields alcohol & CO₂

fermentation:
(1) It is anaerobic respiration carried out by microorganisms
(2) End product of glycolysis is pyruvic acid which can form lactic acid, butyric acid or
alcohol.

Question 6.
What is RQ? Name the apparatus used to measure RQ. (July 2006)
Answer:
The ratio of volumes of CO₂ liberated and O₂ used during respiration is called respiratory quotient. It is denoted by RQ. The RQ values of different substrates can be measured by Ganong’s respirometer.

Question 7.
Give an overall equation for alcoholic fermentation.
Answer:

Question 8.
Write any four differences between aerobic respiration and anaerobic respiration.
Answer:
Aerobic Respiration

• In this respiratory substrate is completely oxidized.
• It takes place in the presence of molecular O₂.
• End products of this process are CO₂ and H₂O.
• More amount of energy is liberated.

Anaerobic respiration.

• A respiratory substrate is incompletely oxidized.
• It takes place in the absence of molecular O₂.
• End products are ethyl alcohol and CO₂.
• Less amount of energy is liberated.

Question 9.
Write any two differences between alcoholic fermentation and Lactic acid fermentation.
Answer:
Alcoholic Fermentation

• End products of alcoholic fermentation are ethyl alcohol and CO₂.
• This process is carried out by yeast.

Lactic acid fermentation.

• The end product of lactic acid fermentation is lactic acid.
• This process is carried out by lactic acid bacteria present in milk.

Question 10.
What is fermentation? Give the equation for alcoholic fermentation. (Oct. 2004)
Answer:
Anaerobic respiration carried out by microorganisms is called fermentation.
C₆H₁₂O₆ → 2C₂H₅OH+ 2C₂O ↑+ energy

1st PUC Biology Respiration in Plants Five Marks Questions

Question 1.
Draw labelled diagram and describe the structure and function of a mitochondrion.
(Apr. 83, 87, Oct. 86)
Answer:
Diagram under Q.1 of two marks.
Mitochondria called the powerhouse of the cell are the organelles of cellular respiration. The mitochondria are bounded by a double unit membrane space. The outer membrane is smooth and the inner folded repeatedly into projections called cristae. The central portion of the mitochondrion encloses the matrix.

The matrix side of the inner membrane, including surfaces of cristae are bounded by lollipop like structures called Rackers particles or F0F1 complexes which help in ATP synthesis. Molecules necessary for electron transport are present. The matrix contains highly concentrated mixture of several enzymes Associated with Kreb’s cycle! The matrix has DNA, RNA, and 70s type of ribosomes.

Question 2.
Explain the conversion of hexose sugar into pyruvic acid during respiration.
OR
Write the schematic representation of glycolysis. (Oct. 84, 96, 97, 99, 03, Apr. 91, 95, 97, 01, 06, July 06, 07, 2010, M.Q.P.)
Answer:
Glycolysis is the breakdown of glucose into pyruvic acid also called EMP pathway after the scientists Embden, Meyerhof and Paranas and is seen in the Cytoplasm. It involves several steps, Glucose in the presence of ATP is converted to glucose 6 phosphate which by isomerisation forms fructose -6- phosphate and by second phosphorylation forms fructose 1-6 diphosphate.

This fructose 1 -6 diphosphate a 6 Carbon compound breaks up into 2 molecules of PGAL and DHAP both being 3 Carbon compounds. Each compound then by phosphorylation and dehydrogenation combine with IP and NAD to yield 1,3 di PGA and NADH2. The di PGA by dephosphorylation gives ATP and’3 PGA which by rearrangement produces 2PGA. Dehydration of 2PGA yields phosphoenol pyruvate which by dephosphorylation give pyruvic acid.

One molecule of glucose yields 2 molecules of pyruvic acid.
ATP calculion : ATP used – 2 ATP
ATP synthesised NADH₂ formed = 2×3 = 6 ATP
ATP formed = 4 ATP 10 ATP
Net gain = ATP synthesised – ATP used
10-2 = 8 ATP.

Question 3.
Differentiate Respiration from Photosynthesis. (March 1990)
Answer:
(1) Respiration – (a) Photosynthesis

(1) Occurs in all living cells in the cytoplasm and mitochondria.
(a) occurs in cells with chloroplasts.

(2) no segregation into light and dark reactions
(b) Light reactions are totally dependent on light.

(3)Starting compounds are C₆H₁₂O₆ and O₂.
(c) Starting materials are CO₂ and H₂O.

(4)ATP is produced by oxidative phosphorylation.
(d) ATP produced by photophosphorylation.

Question 4.
Give an account of (Kreb’s cycle) Citric acid cycle. (April 1985, 1988, 1989, 1992, 2000, 2006, Oct. 1991, 1993, 2002, 2004, July 2008)
or
Write the schematic representation of the citric acid cycle with the preparatory phase. (July 2011)
Answer:
Kreb’s cycle or citric acid cycle is second step of respiration and takes place in the mitochondrial matrix. Pyruvic acid formed during glycolysis is first converted to acetyl CoA a 2 Carbon compound which in the mitochondrial matrix to initiate Kreb’s cycle.

Condensation: acetyl CoA combines with oxaloacetate in presence of water to give a tricarboxylic acid citric acid. CoA is released.

Dehydration and Hydration:

• The citric acid then loses a molecule of water to form cis-aconitate which takes up a molecule of water and forms isocitrate.
• Dehydrogenation: Isocitrate undergoes dehydrogenation and forms oxalosuccinate. This yields 2 molecules of NADH2.
• Decarboxylation: By giving out CO₂ – oxalosuccinate is converted to α- ketoglutarate.
• Dehydrogenation & decarboxylation: The a- ketoglutarate simultaneously shows dehydrogenation decarboxylation to form succinyl CoA, 2 molecules of CO_2, NADH₂ are released and CoA is added.
• Hydration & Phosphorylation: Succinyl CoA in presence of water forms succinate, CoA is released and 2 GTP’s are synthesised which are converted to ATP.
• Dehydrogenation: Dehydrogenation of succinate yields Fumarate and 2 molecules of FADHO₂ are formed.
• Hydration: Fumarate in presence of water yields Malate.
• Dehydrogenation: Malateby dehydrogenation gives 2 molecules of NADH₂ and is converted to oxaloacetate.

ATP Calculation.
8 NADH2 = 8 × 3 = 24 ATP
2 FADH, = 2 × 2 = 4 ATP
2 GTP =2- = 2ATP
Total =30 ATP

Question 5.
Describe the mechanism of anaerobic respiration. (Oct. 85, 94)
Answer:
Anaerobic Respiration is the respiration carried out in the absence of oxygen and the fuel molecules are partially broken down.
I Step – glycolysis same as 4,
II step – Anaerobic breakdown of glucose.
Glucose produced during glycolysis is converted to substances like ethyl alchohol and

The pyruvate by decarboxylation from acetaldehyde and by hydrogenation gives ethyl alcohol. The overall equation is

C₆H₁₂O₆ → 2C₂H₅OH+ 2C₂O + energy

ATP calculation:
Net gain during glycolysis = 8 ATP
ATP used for (2NADH2) 2×3 =6 ATP
Balance = 2ATP

Question 6.
Define fermentation. Explain the fate of pyruvic acid in Saccharomyces and Lactobacillus (April 2007, March 2010)
Answer:
Anaerobic breakdown of organic food substances into CO₂ ethyl alcohol or lactic acid by the enzymes of some microorganisms is called fermentation. The fate of pyruvic acid in saccharomyces.

In saccharomyces, pyruvate is further oxidized into ethyl alcohol and CO₂ yeast converts pyruvate into ethyl alcohol and CO₂ in the absence of O₂. It is called alcohol or ethanol fermentation.

The fate of pyruvate in lactobacillus The lactobacilli of milk convert pyruvate into lactic acid. It is called lactic acid or lactate fermentation.

CH₃COCOOH+2NADH → C₃H₆O₃ +2NAD⁺