Ch.8 Cell: The Unit Of Life

Question 1

G.N.Ramachandran

Answer 1

Unit 3, Page 86, 1922 - 2001 (79 years)

1) Founder of Madras School of Conformational Analysis of Biopolymers
2) Discovered the Triple Helix structure of Collagen Protein
3) Gave the Ramachandran Plot with Bond Angles to define all the Proteins
4) Influenced by Linus Pauling who gave Alpha Helix and Beta Sheet models of Proteins

Question 2

8.0.0 Introduction

Answer 2

2 Paragraphs, Page 87 - 87

• Paragraph 1
  1) Difference between Living and Non-Living is presence of the Basic Unit of Life (the Cell)
• Paragraph 2
  1) All organisms have Cells
  2) Organisms can be Unicellular (One Cell) Multicellular (Many Cells)

Question 3

8.1.0 What Is A Cell?

Answer 3

2 Paragraphs, Page 87 - 87

• Paragraph 1
  1) Unicellular Organisms can:- (i) Exist Independently (ii) Perform Essential Life Functions
  2) Anything less than complete Cell does not ensure Independent Living. This is why Cell is Fundamental Structural and Functional Unit of Life
• Paragraph 2
  1) Anton Von Leeuwenhoek first saw and described Live Cell
  2) Robert Brown discovered Nucleus
  3) Invention and development of Microscope and later Electron-Microscope revealed all the Structural details of Cell

Question 4

8.2.0 Cell Theory

Answer 4

2 Paragraphs, Page 87 - 88

• Paragraph 1
  1) German Botanist Matthias Schleiden (1838) discovered that All Plants are composed of different Cells

[Page 88]

2) British Zoologist Theodore Schwann (1839) discovered Thin Outer Layer of Animal Cell now called Plasma Membrane
3) Schwann studied Plant Tissues and concluded that presence of Cell Wall is Unique Character of Plant Cell
3) Schwann proposed Hypothesis that Plants and Animal’s are composed of Cells and Products of Cells

• Paragraph 2
  1) Schleiden and Schwann formulated Cell Theory, but couldn’t explain how Cells are formed
  2) Rudolf Virchow (1855) modified the Cell Theory and explained that Cells divide to form new Cells (Omnis Cellula-e Cellula)
  3) Today Cell Theory is:- (i) All Living Organisms are made of Cells and Products of Cells (ii) All Cells come from Pre-Existing Cells

Question 5

8.3.0 An Overview Of Cell

Answer 5

5 Paragraphs, Page 88 - 89

• Paragraph 1
  1) Onion Peel Cells (Typical Plant Cells) have Cell Wall as the Outermost Boundary and just within it is Cell Membrane
  2) Human Cheek Cells have the Plasma Membrane as the Delimiting Structure
  3) Inside each Cell (Plant and Animal) there is a Dense Membrane Bound Structure called Nucleus
  4) Nucleus has Chromosomes that in turn have Genetic Material (DNA)
  5) Cells with Membrane Bound Nucleus are Eukaryotic, and those without Membrane Bound Nucleus are Prokaryotic
  6) Both Eukaryotic and Prokaryotic Cells have Semi-Fluid Matrix called Cytoplasm that occupies volume of the Cell
  7) Cytoplasm is Main Arena of Cellular Activities in both Plant and Animal Cells, and has various Chemical Reactions that keep the Cell in Living State
• Paragraph 2
  1) Besides Nucleus, the Eukaryotic Cells have many other Membrane Bound Organelles like ER, Golgi, Lysosomes, Mitochondria, Microbodies and Vacuoles
  2) Prokaryotic Cells lack such Organelles
• Paragraph 3
  1) Ribosomes are Non-Membrane Bound Organelles that are present in all Cells (both Prokaryotic and Eukaryotic)
  2) Ribosomes are found:- (i) in Cytoplasm (ii) inside Chloroplast (in Plants) and Mitochondria (iii) on RER
• Paragraph 4
  1) Animal Cells have another Non-Membrane Bound Organelle called Centrosome, which helps in Cell Division
• Paragraph 5
  1) Cells differ greatly in Size, Shape and Activities
  2) Mycoplasma are the Smallest Cells (0.3um)

[Page 89]

[Figure 8.1] Cell Shapes

3) Bacteria (3-5um)
4) Ostrich Egg is the Largest Isolated Cell
5) Human RBC (7um)
6) Nerve Cells are some of the Longest Cells
7) Cells can be Disc-Like, Polygonal, Columnar, Cuboid, Thread-Like or even Irregular in shape
8) Shape of Cells may vary with the Functions they perform

Question 6

8.4.0 Prokaryotic Cells

Answer 6

2 Paragraphs, Page 89 - 90

• Paragraph 1
  1) Prokaryotic Cells are represented by Bacteria, Blue-Green Algae, Mycoplasma and PPLO
  2) They are generally smaller and multiply faster than Eukaryotic Cells
  3) They are of many different shapes like:- (i) Bacillus (Rod) (ii) Coccus (Spherical) (iii) Vibrio (Comma) (iv) Spirillum (Spiral)
• Paragraph 2
  1) Prokaryotes exhibit variety of Shapes and Functions but Organisation in Prokaryotes is Fundamentally Similar

[Page 90]

[Figure 8.2] Cell Sizes

2) All Prokaryotic Cells have Cell Wall except Mycoplasma
3) Cytoplasm is Fluid Matrix
4) No well defined Nucleus (Single Chromosome, DS-Circular, Without Membrane)
5) Plasmid is Extra Chromosomal DNA and it gives Unique Phenotypic Characters to Bacteria (Antibiotic Resistance), and can be used to monitor Transformation
6) No Eukaryotic organelles are found in Prokaryotes except Ribosomes
7) Prokaryotes have something unique in the form of Inclusions
8) Mesosome is Infolding of Plasma Membrane and are Characteristic of Prokaryotes

Question 7

8.4.1 Cell envelope and its modifications

Answer 7

6 Paragraphs, Page 90 - 91

• Paragraph 1
  1) Most Prokaryotic Cells (Particularly Bacteria) have Chemically Complex Cells Envelope
  2) Cell Envelope has 3 Tightly Bound Layers (Outer Glycocalyx, Middle Wall, Inner Membrane)
  3) Each layer has Distinct Functions but all together act as Single Protective Unit
  4) Bacteria classified in 2 groups based on differences in Cell Envelope (Gram +ve and Gram -ve)
• Paragraph 2
  1) Glycocalyx differs in Composition and Thickness in different Bacteria. It can be a Loose Sheath called Slime Layer or a Thick and Tough layer called Capsule
  2) Cell Wall determines the Shape of the Bacteria and prevents it from Bursting or Collapsing
• Paragraph 3
  1) Plasma Membrane is Selectively Permeable and Interacts with the Outside World
  2) Plasma Membrane is similar in Eukaryotic and Prokaryotic Cell
• Paragraph 4
  1) Mesosome is Special Membranous Structure formed by Extension of Plasma Membrane into the Cell in the form of Vesicles, Tubules and Lamellae

[Page 91]

2) Mesosome helps in:- (i) Wall Formation (ii) DNA Replication and Distribution to Daughter Cells (iii) Respiration (iv) Secretion (v) Increasing Surface Area and Enzyme Content of Plasma Membrane
3) In some Prokaryotic Cells like Cyanobacteria (Photosynthetic) there are other Membranous Extensions called Chromatophore which have Pigments

• Paragraph 5
  1) Bacteria can be Motile or Non-Motile
  2) Motile Bacteria have Flagella which is Filamentous Extension of Cell Wall
  3) Number and Arrangement of Flagella can be different in different Bacteria
  4) Bacterial Flagella has 3 Parts:- (i) Filament (ii) Hook (iii) Basal Body
  5) Filament is Longest and extends Outwards from Cell Surface
• Paragraph 6
  1) Besides Flagella, Bacteria have other Surfaces Structures that don’t play role in Motility
  2) Pilli are Elongated Tubular Structures made of Special Protein
  3) Fimbriae are Bristle like Fibres sprouting out of Cell
  4) Pilli and Fimbriae are known to help Attach some Bacteria to Rocks in Streams and on Host Tissues

Question 8

8.4.2 Ribosomes and Inclusion Bodies

Answer 8

2 Paragraphs, Page 91 - 91

• Paragraph 1
  1) Ribosomes are site of Protein Synthesis and in Prokaryotes Ribosomes are associated with Plasma Membrane
  2) Prokaryotic Ribosomes are 70s which is made of 50s and 30s and are 15nm by 20nm in size
  3) In Prokaryotes these can be several Ribosomes (Polysome or Polyribosome) attached to a single mRNA for Translation
• Paragraph 2
  1) Reserve material in Prokaryotes are stored in Non-Membrane Bound Inclusion Bodies that lie freely in Cytoplasm
  2) Inclusion Bodies can be:- (i) Phosphate Granules (ii) Cyanophycean Granules (iii) Glycogen Granules
  3) Gas Vacuoles are found in Blue-Green and Purple-Green Photosynthetic Bacteria

Question 9

8.5.0 Eukaryotic Cells

Answer 9

3 Paragraphs, Page 91 -93

• Paragraph 1
  1) Eukaryotes include Protists, Plants, Animals and Fungi
  2) Eukaryotic Cells have Extensive Compartmentalisation of Cytoplasm because of Membrane Bound Organelles
  3) Eukaryotes have Organised Nucleus with Nuclear Envelope
  4) Eukaryotes have various Complex Locomotory and Cytoskeletal Structures
  5) Genetic Material in Eukaryotes is organised into Chromosomes
• Paragraph 2
  1) Plants have structures that Animals don’t have like:- (i) Cell Wall (ii) Plastids (iii) Large Central Vacuole
  2) Animals have structures that (almost all) Plants don’t have like:- (i) Centrioles

[Page 92]

[Figure 8.3] (a) Plant Cell (b) Animal Cell

[Page 93]

• Paragraph 3
  1) Let us now look at individual cell organelles to understand their structure and functions

Question 10

8.5.1 Cell Membrane

Answer 10

7 Paragraphs, Page 93 - 94

• Paragraph 1
  1) Detailed structure of Plasma Membrane was studied after invention of Electron Microscope in 1950
  2) a possible Structure of Plasma Membrane was deduced by doing Chemical Studies on Human RBC Membrane
• Paragraph 2
  1) Plasma Membrane is mainly made of Proteins and Lipids
  2) Main Lipids are Phospholipids arranged in a Bilayer with their Polar Heads towards Outside and Non-Polar Tails (Saturated Hydrocarbons) towards Inside to protect it from Aqueous Environment
  3) Plasma Membrane also has Cholesterol
• Paragraph 3
  1) Later Biochemical Studies showed that Membrane has Carbohydrates and Proteins as well
  2) Ratio of Proteins and Lipids is different in different cells (Human RBC has 52% Protein and 40% Lipid)
• Paragraph 4
  1) Proteins are classified into 2 categories based on Ease of Extraction (Integral and Peripheral)
  2) Peripheral Protein lie on the Surface while Integral Protein are Partially or Totally Buried
  => Figure 8.4:- Fluid Mosaic Model

[Page 94]

• Paragraph 5
  1) An Improved Model of Plasma Membrane (Fluid Mosaic Model) was given by Singer and Nicolson (1972)
  2) Quasi-Fluid nature of Lipids enables Lateral Movement of Proteins. This ability to move is measured as Fluidity of Membrane
• Paragraph 6
  1) Fluid Nature of Membrane is important for:- (i) Growth (ii) Formation of Intercellular Junctions (iii) Secretion (iv) Endocytosis (v) Cell Division
• Paragraph 7
  1) Most Important Function of Membrane is to Transport Molecules across it
  2) Membrane is Selectively Permeable to Molecules on either side of it
  3) Passive Transport is movement of Molecules without energy
  4) Neutral Solutes move across using Simple Diffusion Along Concentration Gradient
  5) Water moves across using Osmosis Along Concentration Gradient
  6) Polar Molecules can only move across the Non-Polar Membrane through Carrier Proteins
  7) Active Transport is movement of few Ions or Molecules Against Concentration Gradient using ATP energy (Na+/K+ pump)

Question 11

8.5.2 Cell Wall

Answer 11

2 Paragraphs, Page 94 - 94

• Paragraph 1
  1) Cell Wall is Non-Living Rigid structure covering the Plasma Membrane in Plants and Fungi
  2) Cell Wall functions to:- (i) Protect from Mechanical Damage and Infection (ii) Cell-to-Cell Interaction (iii) Act as a Barrier to Undesirable Macromolecules
  3) Algae Cell Wall is made of:- (i) Cellulose (ii) Galactans (iii) Mannans (iv) CaCO3
  4) Other Plants have Cell wall made up of:- (i) Cellulose (ii) Hemicellulose (iii) Pectins (iv) Proteins
  5) Young Cell has Primary Wall that is capable of Growth and gradually Diminishes
  6) Mature Cell has Secondary Wall formed on the Inner Side of Cell
• Paragraph 2
  1) Middle Lamella is mainly made of Calcium Pectate
  2) Middle Lamella holds or glues Neighbouring Cells together
  3) Cell Wall and Middle Lamella may be traversed by Plasmodesmata that connect Cytoplasm of Neighbouring Cells

Question 12

8.5.3 Enodmembrane System

Answer 12

11 Paragraphs, 4 Subheadings, Page 94 - 96

• Paragraph 1
  1) Each Membrane Bound Organelle has Distinct Structure and Function but some of them have Coordinated Functions

[Page 95]

2) Endomembrane System has (i) ER (ii) Golgi (iii) Lysosomes (iv) Vacuoles
3) Functions of Mitochondria, Plastids and Peroxisomes are not coordinated with the Endomembrane System

=> 8.5.3.1 Endoplasmic Reticulum (ER)

[Figure 8.5] Endoplamsic Reticulum

• Paragraph 1
  1) ER is a Network (Reticulum) of Tubular structures scattered in Cytoplasm as seen by Electron Microscope
  2) ER divides Intracellular Space into Luminal (inside ER) and Extra-Luminal (Cytoplasm) compartments
• Paragraph 2
  1) ER can have Ribosomes attached to its surface (Rough ER) or it can not have Ribosomes on its surface(Smooth ER)
• Paragraph 3
  1) RER is frequently observed in Cells involved in Protein Synthesis and Secretion
  2) RER is Extensive and Continuous with Outer Membrane of Nucleus
• Paragraph 4
  1) SER is major site for Synthesis of Lipids, and in Animals Lipid-Like Steroid Hormones

=> 8.5.3.2 Golgi Apparatus

[Figure 8.6] Golgi Apparatus

• Paragraph 1
  1) Golgi was discovered by Camillio Golgi (1898)
  2) Golgi is made of Densely Stained Reticular structures near the Nucleus that consist of many Flat, Disc Shaped Sacs or Cisternae (0.5-1.0um in Diameter) stacked Parallel to each other
  3) Golgi has Varied Number of Concentrically Arranged Cisternae near the Nucleus with a Distinct Convex Cis (Forming) Face and the Concave Trans (Maturing) Face

[Page 96]

4) Cis and Trans Face are Entirely Different but Interconnected

• Paragraph 2
  1) Golgi performs function to Package Material to be delivered to Intracellular Targets or to be Secreted
  2) ER Vesicles fuse with Cis (Forming) Face and move towards Trans (Maturing) Face, this is why Golgi remains in close association with ER
  3) A number of Proteins synthesised by Ribosomes on RER are Modified in the Golgi Cisternae before being released from the Trans Face
  4) Golgi is important site for formation of Glycoproteins and Glycolipids

=> 8.5.3.3 Lysosomes

• Paragraph 1
  1) Lysosomes are Membrane Bound Vesicular Structures formed by Packing in Golgi
  2) Lysosomes are rich in almost all types of Hydrolytic Enzymes (Hydrolases - Lipases, Proteases, Carbohydrases)
  3) At Acidic pH these enzymes can digest Carbs, Proteins, Lipids and Nucleic Acids

=> 8.5.3.4 Vacuoles

• Paragraph 1
  1) Vacuoles are Membrane Bound Spaces found in Cytoplasm that contain (i) Water (ii) Sap (iii) Excretory Products (iv) Other Useless Materials
  2) Vacuoles have a Single Membrane called Tonoplast
  3) Plant Vacuoles can occupy 90% of Cell Volume
• Paragraph 2
  1) In Plants the Tonoplast transports number of Ions and Other Materials against the Concentration Gradient, thus their Concentration is significantly higher inside the Vacuole as compared to the Cytoplasm
• Paragraph 3
  1) In Amoeba the Contractile Vacuole is important for Osmoregulation and Excretion
  2) Food Vacuoles in Protists are formed by Engulfing Food Particles

Question 13

8.5.4 Mitochondria

Answer 13

1 Paragraph, Page 96 - 97

• Paragraph 1
  1) Mitochondria are not easily visible unless Specifically Stained
  2) Number, Shape and Size of Mitochondria are variable depending on Physiological Activity of Cell
  3) Mitochondria is typically Sausage Shape or Cylindrical having Diameter of 0.2-1.0um (average 0.5um) and Length 1.0-4.1um

[Page 97]

[Figure 8.7] Mitochondria (Longitudinal Section)

4) Each Mitochondrion has 2 membranes dividing its Lumen into 2 Compartments
5) Inner Compartment is filled with Dense Homogeneous Substances called Matrix
6) Outer membrane forms the Continuous Limiting Boundary of Mitochondria
7) Inner Membrane has number of Infoldings called Cristae that increases Surface Area
8) The 2 membranes have their own Specific Enzymes associated with Mitochondrial Function
9) Mitochondria is Site of Aerobic Respiration (Powerhouse of Cell) and Produces ATP
10) Matrix of Mitochondria has:- (i) Single ds-Circular DNA (ii) RNA (iii) 70s Ribosome (iv) Components for Protein Synthesis
11) Mitochondria divide by Fission

Question 14

8.5.5 Plastids

Answer 14

4 Paragraphs, Page 97 - 98

• Paragraph 1
  1) Plastids are found in All Plant Cells and Euglenoids
  2) Plastids are easily observable as they are Large
  3) Plastids have Specific Colours because of Specific Pigments
  4) Plastids can be classified into 3 categories based on Type of Pigment (Chloroplasts, Chromoplast, Leucoplast)
• Paragraph 2
  1) Chloroplasts have Chlorophyll and Carotenoid Pigments for Trapping Light for Photosynthesis
  2) Chromoplast have Fat Soluble Carotenoid Pigments (Carotene, Xanthophylls, etc) that give colours like Yellow, Orange or Red
  3) Leucoplast are Colourless Plastids of Varied Shapes that store Nutrients:- (i) Amyloplasts store Carbs (Starch) ex:Potato (ii) Elaioplasts store Oils and Fats (iii) Aleuroplast store Proteins

[Page 98]

[Figure 8.8] Sectional View of Chloroplast

• Paragraph 3
  1) Majority of Chloroplasts of Green Plants are found in Mesophyll Cells
  2) Chloroplasts are of different shapes:- (i) Lens-Shaped (ii) Ribbon-Like (iii) Spherical (iv) Oval (v) Discoid
  3) they have Length 5-10um and Width 2-4um
  4) They can be 1 per cell in Chlamydomonas to 20-40 per cell in Mesophyll
• Paragraph 4
  1) Chloroplasts are Double Membrane bound with the Inner Membrane being less permeable and enclosing a space called Stroma
  2) Flattened Membraneous Sacs called Thylakoids can be Stacked like a Pile of Coins called Grana or in between the Grana (Intergranal Thylakoids)
  3) In addition there are Flat Membranous Tubules called Stroma Lamellae that connects the Thylakoids of different Grana
  4) The space inside Thylakoid Membrane is called Lumen that has Chlorophyll Pigments
  5) Stroma contains:- (i) Circular ds-DNA (ii) 70s Ribosomes (iii) Enzymes for Carb and Protein Synthesis

Question 15

8.5.6 Ribosomes

Answer 15

2 Paragraphs, Page 98 - 98

• Paragraph 1
  1) Ribosomes are Granular Structures first observed as Dense Particles by George Palade (1953) under the Electron Microscope
  2) Ribosomes are Non-Membrane Bound and are composed of Proteins and RNA

[Figure 8.9] Ribosome

• Paragraph 2
  1) Ribosomes are made of 2 Subunits (Larger and Smaller)
  2) Eukaryotic Ribosomes are 80s (60s + 40s) and Prokaryotic Ribosomes are 70s (50s + 30s)
  3) ‘s’ is Svedbergs Constant that stand for Sedimentation Coefficient and is Indirect Measure of Density and Size

Question 16

8.5.7 Cytoskeleton

Answer 16

1 Paragraph, Page 98 - 98

• Paragraph 1
  1) Elaborate Network of Filamentous Proteinaceous structures present in the Cytoplasm is called Cytoskeleton
  2) Cytoskeleton Consists of:- (i) Microtubes (ii) Microfilaments (iii) Intermediate Filaments
  3) Cytoskeleton are in:- (i) Mechanical Support (ii) Motility (iii) Maintenance of Shape of Cell

Question 17

8.5.8 Cilia and Flagella

Answer 17

2 Paragraphs, Page 99 - 99

• Paragraph 1
  1) Cilia and Flagella are Hair-Like Outgrowths of Cell Membrane
  2) Cilia work like Oars that move either the Cell or the Surrounding Fluid
  3) Flagella are longer and are responsible for Cell Movement
  4) Prokaryotic and Eukaryotic Flagella are Structurally Different

[Figure 8.10] Section of Cilia/Flagella (a) Electron Micrograph (b) Diagram

• Paragraph 2
  1) Electron Microscope study shows that Cilia and Flagella are covered by Plasma Membrane
  2) The Core is called Axoneme that has a number of Microtubules Running Parallel along the axis
  3) Axoneme has Nice Doublets of Peripheral Microtubules that are arranged Radially and are connected to each other by Linkers
  4) Axoneme has a pair of Central Microtubules that are connected by Bridges
  5) Central Microtubules are covered by a Central Sheath which is connected to one Microtubules of each Doublet by a Radial Spoke
  6) This arrangement of Cilia and Flagella is called 9 + 2 array
  7) Cilia and Flagella emerge from Centriole-Like Basal Bodies

Question 18

8.5.9 Centrosome and Centrioles

Answer 18

1 Paragraph, Page 99 - 100

• Paragraph 1
  1) Centrosome usually contains 2 Cylindrical Cartwheel-Like Centrioles that are arranged Perpendicular to each other and are surrounded by Amorphous Pericentriolar Materials
  2) Centrioles are made up of 9 Evenly Spaced Peripheral Fibrils (Triplets) of Tubulin Protein that are Linked to each other
  3) Central Part of Proximal Region of Centriole is a Proteinaceous Hub which is connected to the Tubules of the Triplets by Radial Spokes made of Protein
  4) Centrioles form:- (i) Basal Body of Cilia and Flagella (ii) Spindle Fibres

Question 19

8.5.10 Nucleus

Answer 19

6 Paragraphs, Page 100 - 102

• Paragraph 1
  1) Nucleus was described by Robert Brown (1831)
  2)Flemming used Basic Dyes to Stain Nuclear Material and named it Chromatin

[Figure 8.11] Structure of Nucleus

• Paragraph 2
  1) Interphase Nucleus has:- (i) Nuclear Matrix (ii) One or more Spherical Nucleolus (iii) Highly Extended and Elaborated Nucleoprotein Fibres called Chromatin
  2) Electron Microscopy showed that Nucleus has 2 Membranes that form a barrier between Nucleus and Cytoplasm
  3) The 2 Nuclear Membranes run Parallel and have 10-50nm space between them called Perinuclear Space
  4) Outer Nuclear Membrane is usually Continuous with ER and also has Ribosomes on it
  5) Nuclear Envelope is interrupted by minute Pores formed by the Fusion of the 2 Membranes
  6) Nuclear Pores allow movement of RNA and Proteins in both directions
  7) Normally there is only 1 Nucleus per cell but there can be variations in the number of Nuclei
  8) Some Cells don’t have Nucleus:- (i) RBC of many Mammals (ii) Seive Tube Cells
• Paragraph 3
  1) Nucloplasm contains Spherical Nucleoli and Chromatin
  2) Contents of Nucleolus are continuous with rest of Nucloplasm because it is a Non-Membrane Bound Structure
  3) Nucleolus is a site for Active rRNA synthesis
  4) Larger and more numerous Nucleoli are present in Cells that are involved in Protein Synthesis

[Page 101]

• Paragraph 4
  1) During Cell Division there are Structured Chromosomes in place of Nucleus
  2) Chromatin contains:- (i) DNA (ii) RNA (iii) Basic Histone Proteins (iv) Non-Histone Proteins
  3) One Human Cell has approximately 2 Meter long DNA in its 46 Chromosomes

[Figure 8.12] Chromosome with Kinetochore

[Figure 8.13] Types of Chromosome

• Paragraph 5
  1) Every Chromosome has Primary Constriction (Centromere) that holds the Chromatids together and on its sides are Disk Shaped Kinetochores
  2) Chromosomes can be classified into 4 categories based on Position of Centromere:- (i) Metacentric has Centromere in the middle (ii) Sub-Metacentric has Centromere little away from the middle (iii) Acrocentric has Centromere close to one end (iv) Telocentric has Terminal Centromere

[Page 102]

• Paragraph 6
  1) Some Chromosomes have Non-Staining Secondary Constrictions at a Constant Location that gives the appearance of a small fragment of DNA called Satellite

Question 20

8.5.11 Microbodies

Answer 20

1 Paragraph, Page 102 - 102

• Paragraph 1
  1) Microbodies are Membrane Bound Minute Vesicles containing various Enzymes that are present in both Plant and Animal Cells