1st PUC Biology Question Bank Chapter 8 Cell: The Unit of Life

   

You can Download Chapter 8 Cell: The Unit of Life 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 8 Cell: The Unit of Life

1st PUC Biology Cell: The Unit of Life NCERT Text Book Questions and Answer:

Question 1.
Which of the following is not correct?
(a) Robert Brown discovered the cell.
(b) Schleiden and Schwann formulated the cell theory.
(c) Virchow explained that cells are formed from preexisting cells.
(d) A unicellular organism carries out Its life activities within a single cell.
Answer:
(a) Robert Brown discovered the cell.

Question 2.
New cells generate from
(a) bacterial fermentation
(b) regeneration of old cells
(c) prefix if ting cells
(d) abiotic materials
Answer:
(c) preexisting cells

Question 3.
Match the following
(a) Cristae – (i) Flat membranous sacs in stroma
(b) Cisternae – (ii) Infolding in mitochondria
(c) Thylakolds – (iii) Disc-shaped sacs in Golgi apparatus
Ans:
(a) – (ii)
(b) – (iii)
(c) – (i)

Question 4.
Which of the following is correct:
(a) Cells of all living organisms have a nucleus.
(b) Both animal and plant cells have a well-defined cell wall.
(c) In prokaryotes, there are no membrane-bound organelles.
(d) Cells are formed denovo from abiotic materials.
Answer:
(c) In prokaryotes, there are no membrane-bound organelles.

Question 5.
What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
Answer:
Mesosome is infolded of the plasma membrane of a Gram-positive bacterium. It increases the surface area of the respiratory membrane and also helps in the replication of DNA and their separation.

KSEEB Solutions

Question 6.
How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it In the same way? If not, then how are these transported across the membrane?
Answer:

  1. Neutral solutes move across the plasma membrane by simple diffusion along a concentration gradient (from higher concentration to the lower).
  2. Water moves like this way. Osmosis is the movement of water by diffusion.
  3. The polar molecules may not pass through the non-polar bilipid layer, they require a carrier protein of membrane for transport across it. Few ions are transported by Na+/K+ pump by active transport.
  4. Such transport is an energy-dependent process, in which ATP is utilized and is called active transport.

Question 7.
Name two cell-organelles that are double membrane-bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
Answer:
Cell organelles that are double membrane-bound are

  • Mitochondria
  • Chloroplasts

1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 1
Its a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments i.e. outer compartment and inner compartment. The inner compartment is called a ‘matrix’. The inner membrane forms a number of infoldings called the cristae towards the matrix. Two membranes have their own specific enzymes associated with mitochondrial function.
Mitochondria are the sites of aerobic respiration.

They produce cellular energy in the form of ATP and called the ‘power houses’ of the cell. The matrix also possesses a single circular DNA molecule, a few RNA molecules, ribosomes (FOS), and the components required for the synthesis of proteins.
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 2
Chloroplasts are the plastids that contain chlorophyll pigments which are present in plant cells and euglenoids. The space limited by the inner membrane of the chloroplast is called the ‘stroma’. Stroma contains number of organised flattened membranous sacs called the thylakoids. Thylakoids are arranged in stacks called ‘grana’. Different grana are connected by flat membranous tubules called stroma lamellae. Space inside thylakoids is called lumen.

The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrates and proteins. Its the site of dark reaction. Chlorophyll pigments are present in the thylakoids which along with carotenoid pigments are responsible for trapping light energy essential for photosynthesis. Grana is the site of light reaction.

Question 8.
What are the characteristics of prokaryotic cells?
Answer:
Characteristic of prokaryotic cells:

  • These are represented by PPLO, Mycoplasma, BGA and bacteria.
  • These are smaller in size and multiply more rapidly.
  • Vary greatly in size and shape.
  • All prokaryotes have cell wall enclosing cell membrane, cytoplasm and circular DNA (plasmid/naked chromosome) that is not bounded by nuclear membrane.

Question 9.
Multicellular organisms have division of labour. Explain.
Answer:
In Multicellular organisms, different group of cells perform different tasks in sustaining an ‘organism- Each group of cells perform a well defined task which is different from others but interact and co-operate with other cells. For eg: conduction by nerve cells, secretion by gland cells, red blood and white blood cells found in the blood etc. Thus multicellular organisms exhibit division of labour.

KSEEB Solutions

Question 10.
Cell is the basic unit of life. Discuss in brief.
Answer:
The cells are not only the building blocks of the body but also the functional units of life. In fact, the activities of an organism are the sum total of coordinated activities of its constituent cells. All new cells of an organism arise from the pre-existing ones and hence each cell has the same genetic information and is capable of giving rise to a complete individual. This potential of the cell is termed as totipotency. Each cell has several organelles and the cell performs all functions through these organelles present in the cytoplasm. Since most of the activities of an organism are present in miniature form in each and every cell, the cell can be called a functional unit of life.

Question 11.
What are nuclear pores? State their function.
Answer:
Nuclear pores: Electron microscopy has revealed that the nuclear envelope contains two parallel membranes and space (10 nm-50 nm) between them. The outer membrane has small pores called the nuclear pores formed by the fusion of two membranes.
Function: Nuclear pores are the passages through which the movement of RNA and protein molecules occurs in both the directions between the nucleus and cytoplasm.

Question 12.
Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
Answer:
Lysosomes are membrane-bound vesicular structures formed by the process of packaging in the Golgi apparatus. The isolated lysosomal vesicles have been found to be very rich in almost all types of hydrolytic enzymes (called hydrolases lipases, proteases, carbohydrases) optimally active at the acidic pH. These enzymes are capable of digesting carbohydrates, proteins, lipids, and nucleic acids.

The vacuole is the membrane-bound space found in the cytoplasm. It contains water, sap, excretory product and other materials not useful for the cell. The vacuole is bound by a single membrane called a tonoplast. In-plant cells the vacuoles can occupy up to 90 percent of the volume of the cell. In plants, the tonoplast facilitates the transport of a number of ions and other materials against concentration gradients into the vacuole, hence their concentration is significantly higher in the vacuole than in the cytoplasm

In amoeba, the contractile vacuole is important for excretion. In many cells, as in protists, food vacuoles are formed by engulfing the food particles.

Question 13.
Describe the structure of the following with the help of labelled diagrams.
(i) Nucleus
(ii) Centrosome
Answer:
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 3
Nucleus contains nucleoprotein fibres called chromatin, nuclear matrix and one or more spherical bodies called nucleoli. It consists of two parallel membranes with space between them called the perinuclear space which forms the barrier between the materials present inside the nucleus and that of the cytoplasm. The outer membrane is continued with the endoplasmic reticulum and bears ribosomes on it. Nuclear pores which are formed by the fusion of its two membranes are the passages through which movement of RNA and protein molecule takes

place in both directions. The content of nucleolus is continuous with rest of the nucleoplasm and it is a site for active ribosomal RNA synthesis. Chromatin contains DNA and some basic proteins called histones, some nonhistone proteins and also RNA.

(ii) Centrosome
Centrosome is an organelle usually containing two cylindrical structures called centrioles. They are surrounded by amorphous pericentriolar materials. Both the centrioles in a centrosome lie perpendicular to each other. They areV ma.de up of nine evenly spaced peripheral fibrils of tubular protein. Each of the peripheral fibril is a triplet. The adjacent triplets are also linked. The central part of the proximal region of the centriole is also proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spates made of protein.

Question 14.
What is a centromere? How does the position of the centromere form the basis of the classification of chromosomes? Support your answer with a diagram showing the position of the centromere on different types of chromosomes.
Answer:
Each chromosome bears genes the units of hereditary information and shows a constricted part called the centromere. Every chromosome essentially has a primary constriction of the centromere on the sides of which disc-shaped structures called kinetochores are present. Based on the position of the centromere the chromosomes can be classified into four types: The metacentric chromosome has a middle centromere forming two equal arms of the chromosome.

The sub-meta centric chromosome has a centromere nearer to one end of the chromosome resulting in one shorter aim and one long arm. In the case of the acrocentric chromosome, the centromere is situated close to its end forming one extremely short and one very long arm, whereas the telocentric chromosome has a terminal centromere. Sometimes a few chromosomes have non-staining secondary constrictions at a constant location. This gives the appearance of a small fragment called the satellite.

1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 4

1st PUC Biology Cell: The Unit of Life Additional Questions and Answers

1st PUC Biology Cell: The Unit of Life One Mark Questions

Question 1.
Who proposed the cell theory?
Answer:
Schleiden and Schwann.

Question 2.
What is nucleoplasm?
Answer:
Fluid present inside the nucleus is called nucleoplasm.

Question 3.
How many layers are in the nucleus?
Answer:
Two

Question 4
Who discovered Nucleus?
Answer:
Robert Brown

Question 5.
Which is the largest known cell?
Answer:
Egg of birds (Ostrich)

KSEEB Solutions

Question 6.
What are the chemical components of middle lamella?
Answer:
Calcium and Magnesium pectate.

Question 7.
Which is the smallest known cell?
Answer:
Mycoplasma gallisapticum.

Question 8
Who first used the term plastids?
Answer:
A.F.W. Schimper.

Question 9.
Who proposed the fluid Mosaic model of Plasma membrane. (Bijapur. 04)
Answer:
S.J. Singer and G.Nicolson.

Question 10.
What are plasmodesmata?
Answer:
The cytoplasmic connection between the cells is called Plasmodesmata

Question 11.
What is Rough/ smooth endoplasmic reticulum?
Answer:
The endoplasmic reticulum with ribosomes is called the Rough endoplasmic reticulum. The endoplasmic reticulum without ribosomes is called the smooth endoplasmic reticulum.

Question 12.
Name the membrane around Vacuole,
Answer:
Tonoplast. (B’lore South. 04)

Question 13.
Which is the site of dark reaction In Chloroplast?
Answer:
Stroma

Question 14.
What are Frets?
Answer:
Membranous links interconnecting the grana of the chloroplast are called frets.

Question 15.
Which is the site of light reaction in chloroplast?
Answer:
Grana (membranes of Thylakoids of grana)

Question 16.
What is granum?
Answer:
Membrane-bound flattened sacs appear like a pile of coins present in the stroma of chloroplast is called Granum.

Question 17.
Write two subunits of 70S ribosome / 80S ribosome.
Answer:
Subunits of 70s ribosomes are 50s and 30s. Subunits of the 80s ribosomes are 60s and 40s.

Question 18.
What is the Svedberg unit?
Answer:
A measure of the size of a particle as determined by centrifugation and it is designated as ‘S’

Question 19.
What are Thylakoids?
Answer:
Membrane-bound flattened sacs of granum are called thylakoids.

Question 20.
Expand RER. (Gulbarga. 04)
Answer:
Rough endoplasmic reticulum.

Question 21.
Name the hard secondary cell wall material of conducting cells of the plant body.
Answer:
Lignin.

Question 22.
Name the matrix of the chloroplast.
Answer:
Stroma

Question 23.
Expand ATP.
Answer:
Adenosine Triphosphate.

Question 24.
Which cytoplasmic organelles are suicide bags called?
OR
Which cell organelle Is also called the “Suicide bag” of cells? (Gulbarga. 2004)
Answer:
Lysosomes.

Question 25.
What Is Chromatin?
Answer:
The darkly stainable thread-like structure found in the nucleus is called chromatin.

Question 26.
Name the powerhouse of the cell.
Answer:
Mitochondria. (Belgaum. 04)

KSEEB Solutions

Question 27.
What are cristae?
Answer:
Folds of the inner membrane of mitochondria are called Cristae.

Question 28.
Name any one function of animal cell vacuole.
Answer:
Osmoregulation (in protozoans).

Question 29.
What is Tonoplast? (B’lore South. 04)
Answer:
The membrane covering the vacuole is called a tonoplast.

Question 30.
Which is the controlling centre of the cell?
Answer:
Nucleus. (B’lore North. 04)

Question 31.
Which cell organelle in animals helps in the formation of aster fibres during cell division? (B’lore North. 2004)
Answer:
Centrosome with Centrioles.

Question 32.
Name the site of protein synthesis.
Answer:
Ribosomes. (Shimoga. 04)

Question 33.
Which is the Protein Factory of the cell?
Answer:
Ribosome (D.Kannada 2006)

Question 34.
What did Schwann propose in his hypothesis?
Answer:
Schwann proposed that the bodies of animals and plants are composed of cells and products of cells.

Question 35.
Give any two organelles present in a eukaryotic cell.
Answer:
Endoplasmic Reticulum, mitochondria.

Question 36.
What are the four basic shapes of bacteria?
Answer:
Bacillus (rod), coccus (spherical), vibrio (comma-shaped), and spirillum (spiral).

Question 37.
What are plasmids?
Answer:
In addition to the genomic DNA, many bacteria have small circular DNA outside the genomic DNA called plasmids.

Question 38.
What are gram-positive and gram-negative bacteria?
Answer:
When bacterias are stained, few take up the gram stain and are called gram-positive, others which do not are called gram-negative.

Question 39.
What is bacterial flagellum composed of?
Answer:
The bacterial flagellum is composed of filament, hook, and basal body.

Question 40.
What are inclusion bodies?
Answer:
Inclusion bodies are the reserve material in prokaryotic cells which are stored in the cytoplasm.

Question 41.
How are lipids arranged in the plasma membrane?
Answer:
Lipids are arranged in the plasma membrane with the polar head towards the outer sides and the hydrophobic tails towards the inner part.

Question 42.
What are peripheral and integral proteins?
Answer:
Peripheral proteins are the membrane proteins that lie on the surface of the membrane while the integral proteins are partially or totally buried in the membrane.

Question 43.
What does the fluid mosaic model state?
Answer:
According to the fluid mosaic model, the quasifluid nature of lipid enables the lateral movement of proteins within the overall bilayer.

Question 44.
What is passive transport?
Answer:
The movement of molecules across the plasma membrane without any requirement of energy is called passive transport.

Question 45.
What is active transport?
Answer:
A few ions or molecules are transported across the plasma membrane against their concentration gradient with the utilisation of ATP (energy). This transportation is called active transport.

Question 46.
What is the composition of the cell wall in plants?
Answer:
The cell wall is made of cellulose, hemicellulose, pectins, and proteins in plants.

Question 47.
What is the rough endoplasmic reticulum?
Answer:
The endoplasmic reticulum bearing ribosomes on their surface is called the rough endoplasmic reticulum.

Question 48.
Who discovered the Golgi apparatus?
Answer:
Camillo Golgi.

Question 49.
What are Lysosomes?
Answer:
Membrane-bound vesicular structures formed by the process of packaging in the Golgi apparatus are called lysosomes.

Question 50.
What does vacuole contain?
Answer:
The volume contains water, sap, excretory product, and other materials not useful for the cell.

Question 51.
Why mitochondria is called the powerhouse of the cell?
Answer:
Mitochondria is the site of aerobic respiration and produces cellular energy in the form of ATP. Hence, it is called as ‘power houses’ of the cell.

Question 52.
Name the three types of plastids?
Answer:
Chloroplasts, chromoplasts and leucoplasts.

Question 53.
Name the types of leucoplasts?
Answer:
Amyloplasts, elaioplasts and aleuroplasts.

Question 54.
What are leucoplasts?
Answer:
Leucoplasts are colourless plastids that store nutrients like carbohydrates, oils, fats and proteins.

Question 55.
What are ribosomes?
Answer:
Ribosomes are granular structures composed of ribonucleic acid (RNA) and proteins.

Question 56.
What is a hub?
Answer:
The central part of the proximal region of the centrio’s is called the hub.

Question 57.
What does chromatin contain?
Answer:
Chromatin contains DNA and some basic proteins called histones, some nonhistone proteins, and RNA.

Question 58.
What is a satellite?
Answer:
Non-staining secondary constrictions at a constant location of chromosomes which appear like a small fragment is called the satellite.

1st PUC Biology Cell: The Unit of Life Two Marks Questions

Question 1.
Write 4 differences between plant cell and animal cell. (Belgaum. 04)
Answer:

  • Plant cells have cell wall Animal cells lack cell wall
  • Plant cells contain Plastids Plastids are absent in Animal cells.
  • Centrioles are absent in Plant cell. Centrioles are present in Animal cell.
  • Vacuoles are large and well developed in plant cells. Vacuoles are small in animal cells.

Question 2.
Mention any two functions of Nucleus.
Answer:

  • DNA present in the chromosomes is the primary hereditary material.
  • Nucleolus of nucleus synthesize the necessary molecules required for the production of ribosome
  • Biosynthesis of DNA and its replication occurs in Nucleus.
  • RNA synthesis takes place in the nucleus.

Question 3.
Write two functions of Centrlole.
Answer:

  • Centriole plays important role in the initiation of cell division in animal cells.
  • Modified centrioles are involved in the formation of locomotory organelles like cilia and flagella.

KSEEB Solutions

Question 4.
Draw the fluid mosaic model of plasma membrane and explain. (B. North 04, Tumkur2008)
Answer:
It is outer most layer in the animals most layer in the animal cell and in plant cell plasma membrane is present below the cell wall. Plasma membrane is also known as plasmalemma or cell membrane. The term plasma membrane was coined by Nageli and Crammer. It is composed by of lipid and protein hence the name lipoprotein membrane. To explain the structure of plasma membrane, several structural models have been proposed viz.

1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 5

  • Sandwich model of Danielli and Davson.
  • Unit membrane model of Robertson.
  • Fluid-mosaic model of Singer and Nicholson.

Among these models the fluid mosaic model of Singer and Nicholson is widely accepted. According to this model lipid molecules are arranged in two layers with their hydrophilic ends facing the periphery and hydrophobic ends facing the center. Protein globules are dispersed in these lipid layers. The extrinsic proteins are found scattered on the inner and outer layers forming a mosaic. The intrinsic proteins are present within the lipid bilayer. Proteins show mobility and behave like icebergs floating in the sea.

Question 5.
State one function of
(a) Mitochondria
(b) Ribosome.
Answer:
(a) Mitochondria: It provides the energy needed for the activities of the cell.
(b) Ribosome: They help in protein synthesis.

Question 6.
Write functions of plant cell wall?
Answer:

  • Cell wall gives a definite shape to the cell.
  • It protects the cell from mechanical damage and infection
  • It helps in the cell to cell interaction and provides a barrier to undesirable macromolecules.
  • It provides rigidity and mechanical support to the cell.

Question 7.
What are unicellular organisms? Give examples.
Answer:
Organisms that contain only a single cell in their body are called unicellular organisms
e.g. amoeba, euglena, etc.

Question 8.
What are multicellular organisms? Give examples.
Answer:
Organisms that are made up of two or more cells are called multicellular organisms
eg: birds, fish, frog, etc.

Question 9.
What is glycocalyx? Give types of glycocalyx In bacteria.
Answer:
The outermost layer of the cell envelope in bacteria is called the glycocalyx.
Two types of glycocalyx are:-

  • Slime layer – which is a loose sheath
  • Capsule – which is thick and tough.

Question 10.
Give the composition of the bacterial flagellum. Which is the longest portion?
Answer:
Bacterial flagellum is composed of three parts, viz filament, hook and the basal body. The filament is the longest portion and extends from the cell surface to the outside.

Question 11.
What are pill and fimbriae? What is its function?
Answer:
Pilli and fimbriae are surface structures of the bacteria. The pills are elongated tubular structures made of a special protein. The fimbriae are small bristle-like fibers sprouting out of the cell. They help in attaching the bacteria to the rocks and to the host tissues.

Question 12.
What is the importance of fluid mature of membranes regarding cell function?
Answer:
The fluid nature of the membrane is important from the point of view of functions like cell growth, the formation of intercellular functions, secretion, endocytosis, cell division, etc.

Question 13.
What is middle lamella? What is it made of?
Answer:
’Middle lamella is the layer of the cell wall that holds or glues the different neighbouring cells together. It is made of calcium pectate.

Question 14.
Differentiate between rough and smooth endoplasmic reticulum.
Answer:

Rough ER Smooth ER
(i) Contain ribosomes on their surface (i) Do not contain ribosomes
(ii) Involved in protein synthesis and secretion (ii) Involved in the synthesis of lipids
(iii) Extensive and continuous with the outer membrane of the nucleus (iii) Not continuous with the outer membrane of the nucleus.

Question 15.
Differentiate between rough and smooth endoplasmic reticulum.
Answer:

Rough ER Smooth ER
(i) Contain ribosomes on their surface
(ii) Involve in protein synthesis and secretion
(iii) Extensive and continuous with the outer membrane of the nucleus.
(i) Do not contain ribosomes
(ii) Involved in the synthesis of lipids
(iii) Not continuous with the outer membrane of the nucleus.

Question 16.
What are cisternae? Name two types of cisternae.
Answer:
Cisternae are the disc-shaped sacs found in Golgi apparatus. These are stacked parallel to each other. The cisternae are concentrically arranged near the nucleus with distinct convex ‘cis.’ or the forming face and concave ‘trans’ or the maturing face.

Question 17.
What are the functions of Golgi bodies?
Answer:

  • It performs the function of packaging materials; to be delivered either to the intracellular targets or secreted outside the cell.
  • Proteins synthesized by ribosomes on the endoplasmic reticulum are modified in the Golgi apparatus.
  • It is the site of the formation of glycoproteins and glycolipids.
  • Golgi cisternae form the primary lysosomes by budding.

Question 18.
Write short notes on
(a) Lysosomes
(b) Vacuoles
Answer:
(a) Lysosomes:
It is a membrane-bound vesicular structure formed by the process of packaging in the Golgi bodies. They are found to be very rich in hydrolytic enzymes like lipases, proteases, carbohydrases, etc. which help in digesting carbohydrates proteins, lipids and nucleic acids.

(b) Vacuoles:
Vacuole is the membrane-bound space found in the cytoplasm which contain water, sap, excretory product and other unwanted materials for the cell. It is bound by a single membrane called tonoplast. In plants, vacuoles can occupy 90% volume of the cell and tonoplast facilitates the transport of a member of ions and other materials against a concentration gradient into the vacuole.

Question 19.
What is cytoskeleton? What is its function?
Answer:
An elaborate network of filamentous proteinaceous structures present in the cytoplasm is collectively referred to as the cytoskeleton. The cytoskeleton are involved in many functions such as mechanical support, motility, maintenance of the shape of the cell.

1st PUC Biology Cell: The Unit of Life Three Marks Questions

Question 1.
Who proposed cell theory? Who modified it and what does it suggest?
Answer:
Cell theory was proposed by Schleiden and Schwann. Rudolf Virchow modified the hypothesis and explained the theory as:

  • All living organisms are composed of cells and products of cells.
  • All cells arise from preexisting cells.

Question 2.
Differentiate between prokaryotic and eukaryotic ceil.
Answer:

Prokaryotic Eukaryotic
(i) These cells lack a membrane-bound nucleus and other membrane-bound organelles
(ii)  They have 70 S ribosomes
(iii) They have plasmids in addition to genomic DNA
(iv) They have a special membranous structure called mesosomes
(v) Gas vacuoles are present
(vi) Cell wall is always present and made of peptidoglycan.
(i) These cells have a membrane-bound nucleus and other membrane-bound organelles
(ii) They have 80 S ribosomes
(iii) They have chromo­somes which contain DNA
(iv) They do not contain mesosomes
(v) Sap/food/contractile vacuoles are present
(vi) Cell wall is present in plants and absent in animals.

Question 3.
What are inclusion bodies? Name all the types of inclusion bodies.
Answer:
Reserve material in prokaryotic cells is stored in the cytoplasm in the form of inclusion bodies. These are not bounded by any mem­brane system and lie free in the cytoplasm.

Phosphate granules, cyanophycean granules, glycogen granules, and gas vacuoles are the types of inclusion bodies. Gas vacuoles are found in blue-green and purple and green photo­synthetic bacteria.

Question 4.
Write a short note on cilia and flagella.
Answer:
Cilia and flagella are hair-like outgrowths of the cell membrane. Cilia are small structures which work like oars causing the movement of either the cell or the surrounding fluid. Flagella are comparatively longer and responsible for cell movement

Cilium and flagellum are covered by a plasma membrane. Their core called axoneme, pos-sesses a number of microtubules running parallel to the long axis. The axoneme has nine pairs of doublets of radially arranged peripheral microtubules and a pair of centrally located microtubules.

The central tubules are connected by bridges and are enclosed by a central sheath, which is connected to one of the tubules of each peripheral doublets by a radial spoke. The peripheral doublets are also interconnected by linkers. Both cilium and flagellum emerge from a centriole structure called the basal bodies.

1st PUC Biology Cell: The Unit of Life Five Marks Questions

Question 1.
Explain Fluid mosaic model Singer and Nicholson Model. (B’lore North 04)
Answer:
Singer and Nicholoson model of plasma membranes is called fluid Mosaic model.
According to this model lipid molecules are arranged in two lagers with their hydrophilic ends face the periphery and hydrophilic ends facing the centre. The protein globules are dispersed in there lipid layers. There are two types of proteins. The extrinsic proteins are found on the periphery arid intrinsic proteins are present within the lipid bilayer. Chain of carbohydrates are found attached to lipid or proteins. This model is a chemical model that explains the arrangement of lipids, proteins and carbohydrates in plasma membrane.

Question 2
Explain the structure of mitochondrion studied under electron microscope. (Gulbarga 2004, B’lore North 2004)
Answer:
Mitochondrion consists of two membranes say outer and inner. The outer membranes is entire but inner membrane has many inward projections called mitochondrial cristae. The space between outer and inner membrane is intermembrane space which continues into the space of cristae. On the surface of cristae there are many lollypop-like F0F1 particles. Inner to the inner membrane, there is matrix, it consists DNA, ribosomes etc. The mitochondrial matrix is the site of Krebs cycle. The F0F1 particles contain certain enzymes and terminal oxidation occurs in this area.

KSEEB Solutions

Question 3.
With a neat labelled diagram explain the ultrastructure of the chloroplast/plastid. (Gulbarga 2004, Belgaum 2004, D.K. 2005, Tumkur2005, Bangalore rural 2005)
Answer:
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 6

  • The chloroplast is a plastid which contains the green coloured pigment chlorophyll.
  • In higher plants, they are discoid in shape and distributed abundantly in the mesophyll tissue of the leaf.
  • They are bounded by a double-layered unit membrane enclosing the intermembrane space.
  • The inner membrane encloses a space called a matrix (stroma matrix) made of carbohydrates, proteins, enzymes, nucleic acids, and ribosomes.
  • Lamellae differentiated as stroma lamellae (unstacked) and grana lamellae (stacked) are found in the matrix. The grana is made of several stacked membranes called thylakoids piled one above the other. They are connected by stroma lamellae/fret membranes and contain photosynthetic units called photosystems/quantasome containing photosynthetic pigments Chi ‘a’, Chi ‘b’, carotenes & xanthophylls.

Function:
Chloroplasts are the main organelles helping in photosynthesis. The thylakoid membranes of granum contain chlorophylls. They harvest light energy and bring light reactions. The stroma of chloroplast consists of many enzymes required for a Dark reaction.

Question 4.
Draw a neat labelled diagram of the ultrastructure of a typical animal cell.
Answer:
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 7

Question 5.
Describe the Fluid mosaic model of the Plasma membrane with a labelled sketch. (B’lore North 2004, M.Q.P.2005, B’lore rural 2005, Kolar2005, Hassan 2005, Mysore 2005, Udupi 2008, D.Kannada 2010)
Answer:
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 8
Singer and Nicholson’s model of plasma membranes is called the fluid Mosaic model.
According to this model lipid molecules are arranged in two lagers with their hydrophilic ends facing the periphery and hydrophilic ends facing the centre. The protein globules are dispersed in between the lipid layers. There are two types of proteins. The extrinsic proteins are found on the periphery and intrinsic proteins are present within the lipid bilayer. Chain of carbo-hydrates are found attached to lipids or proteins. This model is a chemical model that explains the arrangement of lipid, proteins and carbohydrates in plasma membrane.

Question 6.
Draw a neat labelled diagram of the ultrastructure of a typical plant cell.
Answer:
(Shimoga 2004, Chikmagalur 2004, M.Q.P. 2005, Kolar 2005, Mandya 2005, D.Kannada 2006,2007,2008, U.Kannada 2008)
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 9

Question 7.
Describe the structure and functions of the Golgi apparatus /Golgi complex.
(B’lore North, B’lore South. 05, Udupi 06)
Answer:
1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 10
Golgi apparatus/Golgi bodies/Golgisome/ dictyosome was first discovered by Camillo Golgi in the nerve cells of the barn owls. They were called internal reticular apparatus. They are present everywhere, except the cells of prokaryotes, mammalian RBCs, mature sperms, etc. The Golgi complex comprises of cisternae (which are flattened concave lamellae, larger towards the maturation phase and smaller towards the formation phase), tubules (minute tube-like structures found as dialated structures towards the ends of the cisternae), and besides (sac-like structures that are spherical and pinched off from the cisternae). The membranes are unit membranes chemically made of lipo-protein and enclose vitamin C, fatty adds, enzymes, etc.

Functions:

  • They synthesize substances like mucopolysaccharides and enzymes.
  • They produce secretory vesicles.
  • They form the acrosomal cap of the sperm head.
  • In plants cells, they form the cell plate which forms the middle lamella.

Question 8.
Draw a neat labelled diagram of the following cell organelles and explain their structure.
(a) Mitochondria (Gulbarga, Belgaum 04, B’lore South, Hassan. 05, D.K. 2007)
(b) Centrioles (B’lore South, Hassan. 05)
Answer:
Cilium and flagellum are covered by a plasma membrane. Their core called axoneme possesses a number of microtubules running parallel to the long axis. The axoneme has nine pairs of doublets of radially arranged peripheral microtubules and a pair of centrally located microtubules.

1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 11
These were discovered by Kollicker in 1880. The word was coined by Benda. The shape of the mitochondria varies, is bounded by a double unit membrane, outer and inner enclosing a space called the intermembrane space. The outer membrane is smooth while the inner is thrown into folds called cristae. The surface of the cristae is provided with many Lolipop-shaped F0F1 complexes or ATPases or Rackers particles helping in terminal oxidation. The central matrix contains enzymes, respiratory substrates, ATPs, and nucleic acids. The matrix forms the site of the Krebs cycle.

Function:
Mitochondria are storehouses of energy, the so-called ‘Powerhouse of the cell’. Since they contain DNA, they play a role in cytoplasmic inheritance.

1st PUC Biology Question Bank Chapter 8 Cell The Unit of Life 12
These were discovered by Van Banden in 1880. They are characteristic of animal cells only. The centrosome contains two cylindrical bodies called centrioles. They are arranged at right angles to each other: The cytoplasmic region forms the centrosphere. Each centriole shows a whorl of nine triplets of microtubules, embedded in an amorphous matrix and are parallel to each other but form an angle of 40°.

Function:
Centrioles help to organize the spindle fibres during cell division and form astral bodies & fibres from the astral rays. In the sperm one of the centriole forms the axial filament
of the tail.

KSEEB Solutions

Question 9.
Mention the differences between plant cells and animal cells. (B’lore Rural, Mysore 05, D.Kannada. 07,2009)
Answer:
Plant cell – Animal cell

  1. The rigid cell wall of – (1) Cell wall is absent, cellulose
  2. Plastids are – (2) Plastids are absent characteristic
  3. Centrioles are – (3) Centrioles are present, absent
  4. Vacuoles are large – (4) Vacuoles are small prominent
  5. Storage product is (5) Storage product is starch

Question 10.
Write any one function of the cytoplasmic organelles
(a) Ribosome
(b) Endoplasmic reticulum
(c) Golgi body
(d) Nucleolus
(e) cell wall
Answer:
(a) Ribosome – Protein synthesis.
(b) Endoplasmic Reticulum – Major site for synthesis of lipid.
(c) Golgi body – Site of formation of glycoproteins and glycolipids.
(d) Nucleolus – Synthesizes the necessary molecules for the production of ribosomes
(e) Cell wall – Gives shape and protects the cells from damage and infection.

Leave a Comment

error: Content is protected !!