Samacheer Kalvi Class 11 Bio Botany Solutions Chapter 6 Cell The Unit of Life

Tamilnadu Samacheer Kalvi 11th Bio Botany Solutions Chapter 6 Cell The Unit of Life

11th Bio Botany Guide Cell The Unit of Life Text Book Back Questions and Answers

Choose The Right Answers:

Question 1. The two subunits of ribosomes remain united at a critical level of
(a) Magnesium
(b) Calcium
(c) Sodium
(d) Ferrous
Answer: (a) Magnesium
In simple words: The two parts of a ribosome need magnesium to stick together properly. This is key for ribosomes to work well in making proteins.

🎯 Exam Tip: Remember that magnesium ions are crucial for stabilizing the structure of ribosomes, facilitating their role in protein synthesis.

Question 2. Sequence of which of the following is used to know the phylogeny
(a) mRNA
(b) rRNA
(c) tRNA
(d) HnRNA
Answer: (b) rRNA
In simple words: We can understand how different living things are related by looking at the order of building blocks in their rRNA. This helps us see their evolutionary family tree.

🎯 Exam Tip: Ribosomal RNA (rRNA) is a highly conserved molecule, making it very useful for studying evolutionary relationships and phylogeny across different species.

Question 3. Many cells function properly and divide mitotically even they do not have
(a) Plasma membrane
(b) Cyto skeleton
(c) Mitochondria
(d) Plastids
Answer: (d) Plastids
In simple words: Many cells can still work and divide even if they do not have plastids. Plastids are mainly found in plant cells and are involved in processes like photosynthesis.

🎯 Exam Tip: Focus on the specific functions of each organelle; plastids are specialized for plants and algae, so animal cells and some other cell types can thrive without them.

Question 4. Keeping in view the Fluid mosaic model for the structure of cell membrane which one of the following statements is correct with respect to the movement of lipids & Proteins from one lipid mono layer to the other
(a) Neither lipid nor protein can flip flop
(c) While lipid can rarely flip flop proteins cannot
(d) While proteins can flip flop but lipids cannot
Answer: (c) While lipid can rarely flip-flop proteins cannot
In simple words: In the cell membrane, lipids can sometimes flip from one side to the other, but this happens very slowly. Proteins usually cannot flip because they are too big and complex.

🎯 Exam Tip: Understand that "flip-flop" movement is energetically unfavorable for both lipids and proteins, but it is less restricted for smaller lipid molecules compared to large proteins.

Question 5. Match the columns and identify the correct option:
Answer:
(a) Thylakoids - Flat membrane sacs in stroma
(b) Cristae - In folding in Mitochondria
(c) Cisternae - Disc shaped sacs in Golgi apparatus
(d) Chromatin - Condensed structure of DNA
In simple words: Match each part of the cell with its correct description. For example, thylakoids are flat sacs in chloroplasts, cristae are folds in mitochondria, cisternae are sacs in the Golgi body, and chromatin is packed DNA.

🎯 Exam Tip: When matching, focus on the unique structural features and primary locations of each organelle or component to ensure correct pairing.

Question 6. Bring out the significance of Phase Contrast Microscope
Answer: A phase-contrast microscope is special because it allows scientists to see living cells, tissues, and cells growing outside the body (in vitro) during mitosis without staining them. This is very useful because staining usually kills the cells. This microscope works by converting differences in light phase into brightness differences.
In simple words: This microscope helps us see live cells and how they divide without killing them with colors. It makes clear images from slight light changes.

🎯 Exam Tip: Highlight that the phase-contrast microscope enables observation of unstained, living biological specimens, making it invaluable for studying dynamic cellular processes like cell division.

Question 7. State the Protoplasm theory
Answer: The Protoplasm theory, also called the Colloidal theory of Protoplasm, was proposed by Fischer in 1894 and Hardy in 1899. It states that protoplasm is the physical basis of life and acts as a colloidal system. This system contains water, along with many important biological substances like glucose, fatty acids, amino acids, minerals, vitamins, hormones, and enzymes. The theory explains that protoplasm can exist in two states, sol and gel, which can change into each other through a process called gelation and solation. This ability to switch between states is important for the mechanical behavior of cytoplasm.
In simple words: The protoplasm theory says that protoplasm is a colloid (like jelly) that is the main part of life. It contains many important chemicals and can change between a runny liquid (sol) and a thicker jelly (gel), which helps cells move and work.

🎯 Exam Tip: When describing the protoplasm theory, remember to mention its colloidal nature, its key components, and the interconversion between sol and gel states as fundamental aspects of its mechanical behavior.

Question 8. Distinguish between Prokaryotes & Eukaryotes.
Answer:

🎯 Exam Tip: Focus on the presence or absence of a true nucleus and membrane-bound organelles as the primary distinguishing features between prokaryotic and eukaryotic cells.

Question 9. Difference between plant and animal cell:
Answer:

🎯 Exam Tip: Focus on the cell wall, chloroplasts, and vacuole as the main distinguishing features; these are crucial for plant-specific functions like photosynthesis and structural support.

Question 10. Draw the ultrastructure of a plant cell:
Answer:
In simple words: This picture shows a basic plant cell and its important parts. It has a tough outer wall, a cell membrane inside, a big sac called a vacuole, green chloroplasts for sunlight, a nucleus that controls everything, and mitochondria for energy.

🎯 Exam Tip: When drawing a plant cell, ensure you clearly show the cell wall, cell membrane, large central vacuole, nucleus, mitochondria, and chloroplasts, as these are its most characteristic features.

Choose The Right Answer: Part-A

Question 1. Scientist who named the unicellular particles as 'animalcules' ........... .
(a) Aristotle
(b) Robert Brown
(c) Antonie von Leeuwenhoek
(d) Robert Hooke
Answer: (c) Antonie von Leeuwenhoek
In simple words: Antonie von Leeuwenhoek was the scientist who first saw tiny living things through his microscope and called them 'animalcules'. He was a pioneer in microscopy.

🎯 Exam Tip: Remember Antonie von Leeuwenhoek as the "Father of Microbiology" due to his pioneering work with microscopes and discovery of microorganisms, which he called "animalcules."

Question 2. Compound microscope was invented by
(a) Robert brown
(c) Z. Jansen
(d) Zenike
Answer: (c) Z. Jansen
In simple words: The compound microscope, which uses multiple lenses to make things look very big, was first made by Z. Jansen. This invention changed how we study tiny things.

🎯 Exam Tip: Associate Zacharias Jansen with the invention of the compound microscope, a pivotal development in biological science, even though his exact contributions are debated.

Question 3. Micrometry is a technique of measurement of
(a) Microtomy
(b) Nanoparticles
(c) Microscopic Objects
(d) Moving objects
Answer: (c) Microscopic Objects
In simple words: Micrometry is a way to measure very small things, like cells or bacteria, that can only be seen through a microscope. It helps scientists find the exact size of tiny objects.

🎯 Exam Tip: Understand micrometry as a precision technique essential for quantitative analysis of structures and organisms visible only under a microscope.

Question 4. Which of the following electron opaque chemical is used in Electron microscope?
(a) Strontium
(b) Deuterium
(c) Palladium
(d) Uranium
Answer: (c) Palladium
In simple words: To see very small things with an electron microscope, we use chemicals like palladium. These chemicals block electrons and help create a clear image.

🎯 Exam Tip: Recall that electron-opaque heavy metals like palladium or uranium are used in electron microscopy to stain specimens, enhancing contrast by scattering electrons.

Question 5. Who first observed Protoplasm
(a) Corti
(b) Felix Dujardin
(c) Hugo von Mohl
(d) O. Hertwig
Answer: (a) Corti
In simple words: The first person to see protoplasm, which is the living part inside a cell, was Corti. This observation was important for understanding cell structure.

🎯 Exam Tip: Remember that Corti was among the earliest scientists to observe and describe protoplasm, paving the way for later cell theory developments.

Question 6. Dinoflagellates and Protozoa are kept under
(a) MegaKaryotes
(b) Prokaryotes
(c) Eukaryotes
(d) Mesokaryota
Answer: (d) Mesokaryota
In simple words: Dinoflagellates and Protozoa, which have some features of both simple and complex cells, are grouped under Mesokaryota. This group helps classify organisms with unique nuclear structures.

🎯 Exam Tip: Mesokaryota is a distinct category for organisms like dinoflagellates that possess an intermediate nuclear organization, sharing traits with both prokaryotes and eukaryotes.

Question 7. Which among the following is NOT an exception to cell theory?
(a) Viruses
(b) Viroids
(c) Prions
(d) Fungi
Answer: (d) Fungi
In simple words: Fungi are made of cells, so they fit the cell theory. Viruses, viroids, and prions are not considered true cells, so they are exceptions to the theory.

🎯 Exam Tip: Remember that viruses, viroids, and prions lack cellular structure and metabolic machinery, making them key exceptions to the foundational principles of cell theory, unlike multicellular fungi.

Question 8. Mitochondria was named by
(a) A.kolliker
(b) Altmann
(c) Benda
(d) O. Hertwig
Answer: (c) Benda
In simple words: The name "Mitochondria," which refers to the cell's powerhouse, was given by Benda. Before that, they were known by other names.

🎯 Exam Tip: Distinguish between the discovery (Kolliker), initial descriptive terms (Altmann's "bioblasts"), and the eventual naming of mitochondria by Benda.

Question 9. When Thylakoids are stacked together like a pile of coins known as
(a) Grana
(b) Cistemae
(c) Quantosomes
(d) Polysomes
Answer: (a) Grana
In simple words: Inside chloroplasts, flat sacs called thylakoids stack up like coins. Each stack is called a granum (plural: grana), and this is where photosynthesis happens.

🎯 Exam Tip: Visualize the thylakoids as flattened sacs; when multiple thylakoids are stacked, they form a granum, which maximizes surface area for light-dependent reactions.

Question 10. Dense particulars or granules observed by George Palade is known as
(a) Cirtemae
(b) Lamella
(c) Locules
(d) Ribosomes
Answer: (d) Ribosomes
In simple words: George Palade saw tiny, dense particles in cells using his microscope. These particles, which he called ribosomes, are known to be the sites where proteins are made.

🎯 Exam Tip: Remember George Palade's discovery of ribosomes, which are essential organelles responsible for protein synthesis in all living cells.

Question 11. Histone proteins are seen in the DNA of ........... .
(a) Pseudokaryotes
(b) Prokaryotes
(d) Eukaryotes
Answer: (d) Eukaryotes
In simple words: Histone proteins are found with DNA in eukaryotic cells. They help to pack the long DNA strands tightly into the cell's nucleus, forming chromatin.

🎯 Exam Tip: Understand that histone proteins are fundamental for DNA packaging and gene regulation specifically in eukaryotic cells, distinguishing them from prokaryotes.

Question 12. These are also known as Microbodies
(a) Mitochondrial & Ribosomes
(b) Ribosomes & Cistemao
(c) Polysomes & Vacuoles
(d) Peroxisomes & Glyoxysomes
Answer: (d) Peroxisomes & Glyoxysomes
In simple words: Peroxisomes and Glyoxysomes are small, single-membrane organelles that contain specific enzymes for metabolic tasks. They are collectively known as microbodies.

🎯 Exam Tip: Remember that microbodies are a class of small organelles including peroxisomes (involved in hydrogen peroxide breakdown) and glyoxysomes (specific to plants, involved in converting fats to carbohydrates).

Question 13. The organelle made up of nine triplet peripheral fibrils are known as
(a) Microbodies
(b) Tululin
(c) Centrosome
(d) Centroles
Answer: (d) Centroles
In simple words: The centrosome contains two small structures called centrioles. Each centriole is made of nine groups of three tiny tubes arranged in a circle, called triplet peripheral fibrils.

🎯 Exam Tip: The 9+0 arrangement of microtubule triplets is a characteristic feature of centrioles, which are crucial for cell division in animal cells by forming spindle fibers.

Question 14. Fungal cell wall is made of ........... .
(a) Cutin
(b) Chitin
(c) Hemicellulose
(d) Pectin
Answer: (b) Chitin
In simple words: The cell walls of fungi are primarily made of chitin, a strong material similar to what is found in insect exoskeletons. This gives fungi their structural support.

🎯 Exam Tip: Chitin is a defining component of fungal cell walls, distinguishing them from plant cell walls (cellulose) and bacterial cell walls (peptidoglycan).

Question 15. 'Annule' are circular structure seen around
(a) Nuclear membrane
(b) Nuclear Pore
(c) Perinuclear Space
(d) Annuli
Answer: (d) Annuli
In simple words: Annuli are ring-like structures that surround the nuclear pores. These pores allow things to move in and out of the cell's nucleus.

🎯 Exam Tip: Remember that annuli are components of the nuclear pore complex, which regulates the transport of molecules between the nucleus and cytoplasm.

Question 16. The Chromosome that occur in the oocyte of Salamander and in Giant nucleus of Acetabularia is known as
(a) Polytene Chromosome
(b) Lamp brush chromosome
(c) Mitochondrial chromosome
(d) Chloroplast chromosome
Answer: (b) Lamp brush chromosome
In simple words: Lampbrush chromosomes are very large chromosomes found in the egg cells (oocytes) of salamanders and other animals. They have loops that look like a lamp brush and are active in making RNA.

🎯 Exam Tip: Associate lampbrush chromosomes with oocytes and their role in intense gene transcription, as indicated by their characteristic looped structures.

Question 17. Ordinary microscope can be made into Dark Field Microscope (DFM) by means of a special component is called
(a) Patch stop carrier
(b) Secondary Magnification lens
(c) Stage
Answer: (a) Patch stop Carrier
In simple words: An ordinary microscope can become a dark field microscope by adding a special part called a patch stop carrier. This device blocks direct light, making only scattered light visible, so tiny, unstained objects appear bright against a dark background.

🎯 Exam Tip: The "patch stop carrier" or "dark-field stop" is the essential component that converts a bright-field microscope into a dark-field microscope, enabling the visualization of living, unstained specimens against a dark background.

Question 18. In-plant cells, golgi bodies are found as small vesicles called ........... .
(a) Polysomes
(b) Cytosomes
(c) Cytosol
(d) Dictyosomes
Answer: (d) Dictyosomes
In simple words: In plant cells, the Golgi apparatus is made of many small, separate units called dictyosomes. These dictyosomes perform the same functions as the Golgi apparatus in animal cells, like packaging and secreting materials.

🎯 Exam Tip: Differentiate that in plant cells, the Golgi apparatus is often dispersed into individual units known as dictyosomes, rather than the compact structure seen in animal cells.

Question 19. Cisternae, tubule and Vesicles occur in which of the following:
(a) Golgi apparatus
(b) Lysosomes
(c) Endoplasmic reticulum
(d) Glyoxysomes
(i) a & b
(ii) b & c
(iii) c & d
(iv) a & c
Answer: (iv) a & c
In simple words: Cisternae, tubules, and vesicles are found in both the Golgi apparatus and the endoplasmic reticulum. These parts help them sort and move materials around the cell.

🎯 Exam Tip: Remember that cisternae, tubules, and vesicles are characteristic structural components of the endomembrane system, particularly the Golgi apparatus and endoplasmic reticulum, which are interconnected in function.

Question 20. The Golgi apparatus in plant is known as
(a) Dictyosomes
(b) Glyoxysomes
(c) Neo-particles
(d) Microvesides
Answer: (a) Dictyosomes
In simple words: In plants, the Golgi apparatus is not one big structure but is made of many smaller, separate units called dictyosomes. These units carry out the same functions as the Golgi in animal cells.

🎯 Exam Tip: It is crucial to use the term "dictyosomes" when referring to the dispersed units of the Golgi apparatus in plant cells, as this distinguishes them from the more compact structure in animal cells.

Question 21. Which of the three, come under the system of the membrane in Eukaryotic cell
(a) Mitochondria
(b) Nuclear Membrane
(c) Golgi apparatus
(d) Endoplasmic reticulum
(i) a, b & c
(ii) b, c & d
(iii) a, c & d
(iv) a, b & d
Answer: (ii) b, c & d
In simple words: The nuclear membrane, Golgi apparatus, and endoplasmic reticulum all belong to the endomembrane system in eukaryotic cells. Mitochondria, however, are separate. These parts work together to create, move, and store proteins and lipids.

🎯 Exam Tip: The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles, all working collaboratively, but generally excludes mitochondria and chloroplasts.

Question 22. DNA of mitochondrion is ........... .
(a) Helical
(b) Dumbbell
(c) Circular
(d) Spiral
Answer: (c) Circular
In simple words: The DNA found inside mitochondria is typically circular, much like the DNA found in bacteria. This is a key piece of evidence supporting the endosymbiotic theory.

🎯 Exam Tip: Remember that mitochondrial DNA is circular and lacks histones, similar to prokaryotic DNA, which supports the endosymbiotic theory of mitochondrial origin.

Question 23. Fluid droplets are engulfed by membrane, which form vesicles around them
(a) Phagocytosis
(b) Exocytosis
(c) Endocytosis
(d) Pinocytosis
Answer: (d) Pinocytosis
In simple words: When a cell takes in liquid droplets from its outside environment by wrapping its membrane around them, this process is called pinocytosis. It's like the cell "drinking" fluids.

🎯 Exam Tip: Remember that pinocytosis is for liquids, while phagocytosis is for solid particles, both being types of endocytosis where cells bring substances inside.

Question 24. The 60 s large subunit of Eukaryotes contain
(a) 23 s & 5 s - large subunit
(b) 16 s r RNA in large subunit
(c) 18 s r RNA in large subunit
(d) 28 s, 5-8 s and 5 s in large subunit
Answer: (d) 28 s, 5-8 s and 5 s in large subunit
In simple words: The bigger part of a ribosome in eukaryotic cells has three specific types of RNA within it, which are 28S, 5.8S, and 5S ribosomal RNAs. These RNAs are crucial for making proteins.

🎯 Exam Tip: Distinguishing between eukaryotic (80S) and prokaryotic (70S) ribosomal subunits and their RNA components is a common exam point.

Question 25. Elaioplasts store
(a) Starch
(b) Lipid
(c) Protein
(d) Chlorophyll
Answer: (b) Lipid
In simple words: Elaioplasts are special parts of plant cells that are used to keep fats and oils stored. They are a type of plastid that helps the plant save energy.

🎯 Exam Tip: Remember that plastids have different roles; elaioplasts store lipids, amyloplasts store starch, and proteoplasts store proteins.

Question 1. Find out the true and false statements from the following and on that basis find the correct answer True or False with reference to the origin of Eukaryotes.
1. A Prokaryote grow in size and develop infoldings in its cell membrane to increase surface area to volume ratio
2. Aerobic protea bacterium enter eukaryote as prey or parasite and become an endosymbiont
3. Proteobacteria eventually assimilated and became mitochondria
4. Some Prokaryotes go on to acquire additional Exo symbionts the cyanobacteria evolve to become chloroplasts.
(a) True False True False
(b) True True True False
(c) False False False True
(d) False False True True
Answer: (b) True True True False
In simple words: The first three statements are correct: prokaryotes grow by infolding their membrane, bacteria can become endosymbionts, and proteobacteria became mitochondria. However, the last statement about cyanobacteria becoming chloroplasts through additional symbionts is incorrect in this context.

🎯 Exam Tip: The endosymbiotic theory is central to understanding the origin of mitochondria and chloroplasts in eukaryotic cells. Review its key steps carefully.

Question 2. Find out the true and false statements from the following and on that basis And the correct answer
(i) In Prokaryotes the flagellar rotation, only proton movements are involved & not ATP.
(ii) In Eukaryotes to shift the adjacent microtubules to bend cilia or flagella, dynein use energy from ATP
(iii) Bacterial flagella are made up of helical polymers of protein known as Tubulin
(iv) In Eukaryotes the flagella are made up of microtubules and proteins known as dynein and nexin.
(a) True False True False
(b) True True False True
(c) False False True True
Answer: (b) True True False True
In simple words: Prokaryotic flagella use proton movement, and eukaryotic flagella use ATP for movement. Bacterial flagella are not made of tubulin, but eukaryotic flagella are made of microtubules, dynein, and nexin.

🎯 Exam Tip: Pay close attention to the structural and functional differences between prokaryotic and eukaryotic flagella, especially the energy source and protein composition.

Question 3. With reference to Eukaryotic flagellum Find out the true or false statements from the following and on that basis find the correct answer
(i) Flagellum is shorter than cilia as short as 200 μm
(ii) Flagella are microtubule projection of plasma membrane
(iii) Flagella composed of 8 pairs of microtubules with 2 pairs of microtubules in the center
(iv) Structure of Flagella has Axoneme made up of microtubules & protein tubules
(a) True False True False
(b) True True False False
(c) False True False True
Answer: (c) False True False True
In simple words: Cilia are usually shorter than flagella, not the other way around. Flagella are indeed projections of the cell membrane containing microtubules. The internal structure (axoneme) is 9+2 pairs of microtubules, not 8+2. The axoneme is made of microtubules and tubulin protein.

🎯 Exam Tip: A key difference is that flagella are typically longer and fewer than cilia, and both have a characteristic 9+2 microtubule arrangement in their axoneme.

Question 4. Find out the true or false statements from the following and on that basis find the correct answer
(i) Cytoplasm is the physical basis of life
(ii) Cytoplasm inheritance occurs only through the plasma genes
(iii) Cytoplasm serves as a molecular soup where all the cellular organelles are suspended and bound together by a lipid bilayer plasma membrane
(iv) Cytoplasm is a very bad conductor of electricity.
(a) False True True False
(b) True True False True
(c) False True False True
Answer: (a) False True True False
In simple words: The cytoplasm is important but not the sole physical basis of life. Cytoplasmic inheritance is true, and it acts like a soup for organelles. However, cytoplasm is not a bad conductor of electricity.

🎯 Exam Tip: Remember that cytoplasm includes the cytosol and organelles, and its properties are crucial for many cellular processes, including electrical conductivity. Cytoplasm is mainly water, which is an electrical conductor.

Question 5. Find out the true or false statements from the following and on that basis find the correct answer
(i) The contractibility of protoplasm is important for the absorption and removal of water, especially in stomatal operations
(ii) The viscosity of protoplasm is 2-20centipoises
(iii) The protoplasm is made of 10-20% of water
(iv) Brownian movement and Tyndall effect are colloidal properties, so not applicable to protoplasm
(a) False True False True
(b) True False True False
(c) True True False False
(d) True True False False
Answer: (d) True True False False
In simple words: Protoplasm's ability to contract helps with water movement in stomata, and its viscosity is within a specific range. However, protoplasm is mostly water, not 10-20%. Also, Brownian movement and Tyndall effect *are* properties that apply to colloidal systems like protoplasm.

🎯 Exam Tip: Understanding the physical properties of protoplasm, like viscosity and water content, helps explain many cellular functions. Colloidal properties are relevant to protoplasm.

II. Choose The Wrong Match

Question 1. Choose the wrong match.
(a) Cytoplith – Hypodermal leaf cells of ficus bengaliensis
(c) Sphaero raphides – Colocasia
(d) Silica – Oryza sativa
Answer: (d) Silica – Oryza sativa
In simple words: The incorrect match among the given options is Silica – Oryza sativa. This means that Silica is not typically associated with Oryza sativa in the way the other pairs are correctly matched.

🎯 Exam Tip: For "choose the wrong match" questions, carefully evaluate each pair to identify the one where the components are incorrectly associated.

Question 2. Choose the wrong match with reference to mitochondria
(a) Protein – 73%
(b) Lipids – 25-30%
(c) DNA – 12%
(d) RNA – 5-7%
Answer: (c) DNA-12%
In simple words: The DNA content in mitochondria is not 12%. The other percentages for protein, lipids, and RNA in mitochondria are generally considered correct.

🎯 Exam Tip: Remember the typical composition of mitochondria, especially the relative proportions of proteins, lipids, DNA, and RNA, as these are common facts in cell biology.

Question 3. Identify the wrong statement from the following.
(i) Centrosome give rise to spindle fibers in Animal cell
(ii) Golgibodies play important role in packaging and secretion
(iii) Endoplasmic reticulum-SER is involved in protein synthesis
(iv) Vacuoles facilitate the transport of ions and materials in plant cell
Answer: (iii) Endoplasmic reticulum SER is involved in protein synthesis
In simple words: Smooth Endoplasmic Reticulum (SER) is not primarily involved in making proteins; that's the job of Rough Endoplasmic Reticulum (RER) and ribosomes. SER mainly makes lipids and detoxifies substances.

🎯 Exam Tip: Clearly differentiate the roles of RER (protein synthesis) and SER (lipid synthesis, detoxification) to avoid common mistakes.

Question 4. Identify the wrong statement from the following.
(i) The magnification of SEM & its resolving power is – 200000 &5-20nm
(ii) The magnification &resolution power of temis – 1 – 300000&2-10A
(iii) The magnification power of TEM is – 100000 then the light microscope
(iv) The magnification power of phase-contrast – 3 – 40000 & 8-10A microscope
Answer: (iv) The magnification power contrast is microscope & its resolution power – 3-400000 & 8-10A
In simple words: The magnification and resolution ranges stated for phase-contrast microscopes are incorrect. Phase contrast microscopes have lower magnification and resolution compared to electron microscopes.

🎯 Exam Tip: It is important to know the typical magnification and resolving power of different types of microscopes (SEM, TEM, light, phase-contrast) for comparison.

IV. Choose The Right Match From The Following

Question 1. Choose the right match:
(i) Size of mycoplasma – 0.15-0.03 µm
(ii) Size of BGA – 60mm
(iii) Size of RBC – 0.25-0.06 μm
(iv) Size of chick egg – 7-811mm
Answer: (i) Size of mycoplasma – 0.15-0.03μm
In simple words: The correct match here is the size of mycoplasma, which is extremely small, typically ranging from 0.03 to 0.15 micrometers. Mycoplasmas are among the smallest known living organisms.

🎯 Exam Tip: Knowing the approximate sizes of different cells and microorganisms is fundamental in cell biology and helps in comparing cellular structures.

Question 2. Choose the right match:
(i) Volutin granules occur in – Bacteria
(ii) Ttannin – Cassia auriculata
(iii) Calcium carbonate – Mimosa pudica
(iv) Heavy metals – Erchhornia
Answer: (i) Volutin granules- Bacteria
In simple words: Volutin granules are correctly matched with bacteria, as they are phosphate storage granules found in many bacteria. These granules are also called metachromatic granules.

🎯 Exam Tip: Volutin granules are a key identifying feature for certain bacteria, indicating their ability to store inorganic polyphosphate.

Question 3. Choose the right match:
(i) Cell theory – Cortix
(ii) Protoplasm theory – Max Schultze
(iii) Chromosomes physical carriers of genes – Strasburger
(iv) Endoplasmic reticulum wed by – Benda
Answer: (ii) Protoplasm theory – Max Schultze
In simple words: The Protoplasm theory, which states that protoplasm is the physical basis of life, was proposed by Max Schultze. This theory was important in the early understanding of cell biology.

🎯 Exam Tip: It's important to associate key scientific theories and discoveries with the scientists who proposed them, like Max Schultze and the protoplasm theory.

V. Match The Following And Find The Correct Answer:

Question 1. Match the following and find the correct answer:
(i) Harry Beevers – (A) identified Lysosomes a Peroxisomes
(ii) Christian Do Duve – (B) Discovered Glycoxysome c
(iii) A-F-U- Schimper – (C) Coined the word Chromosome
(iv) Waldeyer – (D) Coined the word Plastids
(a) BADC
(b) ABDC
(c) BCDA
(d) CBDA
Answer: (a) BADC
In simple words: The correct matching is Harry Beevers with Glyoxysome, Christian Do Duve with Lysosomes and Peroxisomes, A-F-U- Schimper with Plastids, and Waldeyer with Chromosome. These pairings link scientists with their major contributions to cell biology.

🎯 Exam Tip: Memorize the key discoveries and their associated scientists, especially in historical context, to answer such matching questions accurately.

Question 2. Match the following and find the correct answer:
(i) When the small pieces of golgibody pinches off its tubules to form – A. Chioroplast
(ii) Fernandez moran particles occur in – B. Golgi apparatus
(iii) Zymogen granules occur in – C. Lysosome
(iv) Quantosomes are present in – D. Mitochondria
(a) A D B C
(b) C D B A
(c) A D C B
(d) C D A B
Answer: (d) C D A B
In simple words: When small parts pinch off from the Golgi body, they form lysosomes. Fernandez Moran particles are found in mitochondria. Zymogen granules are found in chloroplasts. Quantosomes are present in the Golgi apparatus.

🎯 Exam Tip: Understanding the origin and location of various cellular structures and their components is crucial for accurate matching.

Question 1. ASSERTION (A): A cell membrane shows fluid behavior REASON (R): A membrane is- a mosaic or composite of diverse lipids and proteins
(a) Assertion and Reason are correct 'R' explaining 'A'
(b) A and R-correct 'R' not explaining A
(c) A is true, but R is wrong
(d) A is true but R is not explaining A
Answer: (a) Assertion A & Reason R are correct R is explaining A
In simple words: The cell membrane acts like a fluid because it is made of many different lipids and proteins that can move around. The fluid mosaic model describes this structure and movement well.

🎯 Exam Tip: The fluid mosaic model is key to understanding cell membrane function. Both the fluidity and the mosaic composition are important for explaining its behavior.

Question 2. Assertion (A): Chloroplast is an important cell organelle performing photosynthesis in plants Reason (R): An organelle is a distinct part of a cell which has a particular structure and function.
(a) A and R are correct R explaining A
(b) A and R correct and R not explaining A
(c) A is true, but R is wrong
(d) A is true but R is not explaining A
Answer: (b) A and R correct R not explaining A
In simple words: The assertion about chloroplasts and photosynthesis is true, and the reason that an organelle has a distinct structure and function is also true. However, the reason does not directly explain *why* chloroplasts perform photosynthesis.

🎯 Exam Tip: In assertion-reason questions, always check if the reason provides a direct and logical explanation for the assertion, not just another true statement.

Question 3. Assertion (A): Mitochondria is uniparental Reason (R): Mitochondria of any one of the parenting divide and gets distributed to daughter cells.
(a) A and R are correct R explaining A
(b) A and R are correct R not explaining A
(c) A is true but R is wrong
(d) A is true but R is not explaining A
Answer: (c) A is true but R is wrong
In simple words: The statement that mitochondria are uniparental (inherited from only one parent, typically the mother) is correct. However, the reason given, which describes mitochondrial division and distribution, is not the correct explanation for uniparental inheritance.

🎯 Exam Tip: Uniparental inheritance refers to the origin of mitochondria from one parent, usually due to the maternal contribution of cytoplasm to the zygote.

Question 4. Assertion (A): The objective of optic lenses of a microscope are interchanged, then it can work as a telescope Reason (R): The objective of the telescope has a small focal length
(a) A and R are correct R explaining A
(b) A and R are correct R not explaining A
(c) A is true but R is wrong
(d) A is true but R is not explaining A
Answer: (d) A is true but R is not explaining A
In simple words: The assertion that interchanging microscope lenses can make it a telescope is true. However, the reason given about a telescope's objective having a small focal length is incorrect, as telescopes typically have a large objective focal length.

🎯 Exam Tip: Understand the basic optics of microscopes and telescopes, particularly the focal lengths of their objective and eyepiece lenses, to avoid confusion.

Question 5. Assertion (A): A polytene achieved by repeated replication of chromosomal DNA without nuclear division. The daughter chromatids aligned side by side called Endomitosis Reason (R): Polytenes is observed in the salivary glands of Drosophila by C.G.Balbiani. 1881.
(a) A and R are correct R explaining A
(b) A and R are correct R not explaining A
(d) A is true but R is not explaining A
Answer: (b) A and R are correct R not explaining A
In simple words: The assertion correctly describes how polytene chromosomes are formed through endomitosis. The reason stating that Balbiani observed them in Drosophila salivary glands is also correct. However, the reason does not explain the process of polytene formation.

🎯 Exam Tip: Polytene chromosomes are excellent examples of gene amplification and are commonly studied in the context of genetics and cytogenetics.

Two Marks Questions

Question 1. Name the scientist who proposed the cell theory.
Answer: Matthias Schleiden and Theodor Schwann are the scientists who proposed the cell theory. Their work established the fundamental principle that all living things are made of cells. This theory is a cornerstone of modern biology.

🎯 Exam Tip: Always remember the names Schleiden and Schwann when asked about the founders of the cell theory.

Question 2. ER- can be referred to as the endoskeleton of the cell. Justify
Answer: Yes, the Endoplasmic Reticulum (ER) can be called the endoskeleton of the cell.
• It connects the plasma membrane and the nuclear membrane, providing structural support to the cytosol.
• It also helps in moving substances within and out of the cell. The ER acts like a dynamic internal framework, crucial for cellular organization.
In simple words: The ER acts like the cell's internal skeleton because it links the outer and inner membranes, giving shape and helping things move inside and outside the cell.

🎯 Exam Tip: When justifying the ER as an endoskeleton, highlight its extensive network and its role in connecting major cellular membranes and transport.

Question 3. Why do we say that viruses are an exception to its cell theory?
Answer: Viruses are considered an exception to the cell theory because they lack protoplasm, which are the essential living parts of a cell. They exist as obligate parasites, meaning they can only reproduce inside other living cells, using the host cell's machinery. Viruses are non-cellular structures, unable to carry out life processes independently.
In simple words: Viruses are not considered true cells because they don't have their own living parts (protoplasm) and need to infect other cells to live and make copies.

🎯 Exam Tip: The key reasons viruses are exceptions are their non-cellular structure, lack of independent metabolism, and obligate parasitic nature.

Question 4. Who said that different kinds of plastids can transform into one another?
Answer: A-F-U Schimper stated that the three different kinds of plastids can transform into one another. This transformation depends on the plant's needs or the specific demands of the plant body. For example, a chloroplast can change into a chromoplast during fruit ripening.
In simple words: The scientist A-F-U Schimper said that different types of plastids in plants can change from one kind to another, depending on what the plant needs.

🎯 Exam Tip: Remember Schimper's contribution to understanding plastid interconversion, which highlights the dynamic nature of plant cell organelles.

Question 5. In a Bright field microscope, where does the primary & secondary magnification occurs?
Answer: In a bright field microscope, primary magnification is achieved by the objective lens. Secondary magnification is then obtained through the eyepiece lens. Together, these two lenses work in sequence to produce the magnified image seen by the observer.
In simple words: The first magnifying happens in the objective lens, and the second magnifying happens in the eyepiece lens of the microscope.

🎯 Exam Tip: Remember the two main lenses in a compound microscope are the objective (closer to the sample) and the eyepiece (where you look), each contributing to the total magnification.

Question 6. State the functions of chloroplast
Answer: The chloroplast is a vital organelle with several key functions:
• It is the primary site of Photosynthesis, the process by which plants convert light energy into chemical energy.
• Light-dependent reactions and dark reactions both occur here, specifically in the granum and stroma, respectively. The chloroplasts also play an important role in Photorespiration, or the C2 cycle, which is a process that affects photosynthetic efficiency.
In simple words: Chloroplasts make food for the plant through photosynthesis. They do this by using sunlight in two main steps: light reactions and dark reactions. They also help in a process called photorespiration.

🎯 Exam Tip: Focus on photosynthesis as the main function and remember the specific locations (granum for light reactions, stroma for dark reactions) within the chloroplast.

Question 7. Distinguish between 70's & 80's Ribosomes.
Answer: Ribosomes are essential for protein synthesis and come in two main types, 70S and 80S, differing primarily in their size and where they are found.

🎯 Exam Tip: Remembering the "S" units (Svedberg units) for ribosome size and their presence in prokaryotes vs. eukaryotes (and organelles) is fundamental.

Question 8. Name the types of cells based on nuclear characteristics.
Answer: The types of cells based on their nuclear characteristics are:
1. Prokaryotes: These cells do not have a true nucleus or membrane-bound organelles.
2. Mesokaryotes: This is an intermediate type, observed in some organisms, with unique nuclear features.
3. Eukaryotes: These cells possess a true nucleus with a nuclear membrane and other membrane-bound organelles.
All living organisms fall into one of these categories depending on how their genetic material is organized.
In simple words: Cells are grouped by how their nucleus is set up: Prokaryotes have no true nucleus, Mesokaryotes are in-between, and Eukaryotes have a true nucleus.

🎯 Exam Tip: The presence or absence of a true nucleus and other membrane-bound organelles is the primary distinction between prokaryotic and eukaryotic cells.

Question 9. Distinguish between glyoxysomes, peroxysomes & sphaerosomes
Answer: Glyoxysomes, peroxisomes, and sphaerosomes are all types of microbodies found in cells, each with distinct roles and characteristics.

🎯 Exam Tip: Remember that all three are microbodies with a single membrane, but their specific enzymatic content and functions differ based on the metabolic needs of the cell and organism.

Question 10. Distinguish between Resolution & Magnification:
Answer: Resolution and magnification are two key aspects of microscopy, often confused, but they refer to distinct capabilities of a lens or microscope.

🎯 Exam Tip: Always remember that high magnification without good resolution results in a blurry, large image. Both are crucial for effective microscopy.

Question 11. Differentiate 4 points of differences between Prokaryotes & Mesokaryotes
Answer: Prokaryotes and Mesokaryotes represent different cellular organizations, particularly regarding their nuclear characteristics and overall complexity.

🎯 Exam Tip: The key differentiator for Mesokaryotes is their unique nuclear division (dinomitosis), which is different from both prokaryotic binary fission and eukaryotic mitosis.

Question 12. Write down any 4 functions of cell wall
Answer: The cell wall is a rigid layer surrounding the plasma membrane of plant cells, fungi, and bacteria, providing crucial support and protection. Here are four of its main functions:
1. Shape: It gives the cell a definite shape and provides rigidity, allowing plants to stand upright.
2. Barrier: The cell wall prevents several molecules from entering the cell, acting as a selective barrier.
3. Protection: It protects the internal protoplasm from mechanical injury and external stresses.
4. Prevents Bursting: By maintaining osmotic pressure, it prevents the cell from bursting when absorbing too much water.
This structural integrity is vital for cell survival and plant health.
In simple words: The cell wall helps the cell keep its shape, stops unwanted things from getting in, protects the cell from harm, and keeps it from bursting by controlling water pressure.

🎯 Exam Tip: When listing cell wall functions, remember its dual role in both providing structural support (shape, rigidity) and offering protection against physical damage and osmotic lysis.

Question 13. Differentiate between TEM and SEM:
Answer:

In simple words: TEM offers high detail and is often used, while SEM gives a 3D view but with less detail, and is used less often.

🎯 Exam Tip: Remember that TEM is for internal structures with high resolution, and SEM is for surface topography with a 3D effect.

Question 14. Explain signal transduction:
Answer: Signal transduction is a process where a cell receives information from outside and responds to it. Nitric oxide acts as a main signaling molecule. The cell membrane is the place where chemical signals interact for signal transduction. Cells communicate by changing signals from one form to another.
In simple words: Signal transduction is how cells get messages from outside and act on them. It often involves steps like a signal binding to a receptor on the cell's surface, which then triggers changes inside the cell.

🎯 Exam Tip: When explaining signal transduction, remember to mention the external signal, the receptor, and the cellular response. A simple diagram can help illustrate the process clearly.

Question 15. Draw the structure of the Golgi apparatus & label its parts.
Answer: The Golgi apparatus is a cell organelle that processes and packages proteins and lipid molecules. It is also involved in making lysosomes. It is found in most eukaryotic cells.
In simple words: The Golgi apparatus looks like stacked flattened sacs. It has a 'cis' side where things enter and a 'trans' side where processed materials exit in vesicles.

🎯 Exam Tip: Remember to clearly label the cis face (receiving side), trans face (shipping side), and the cisternae (flattened sacs) in your diagram. Also, show vesicles budding off.

Question 16. What is the cell wall composition of the following organism?
(a) Fungi
(b) Bacteria
(c) Algae
Answer:
(a) Fungi - Chitin and fungal cellulose.
(b) Bacteria - Peptidoglycan
(c) Algae - Cellulose, mannan and galactan.
In simple words: The outside layer of a cell, called the cell wall, is made of different things in different living beings. Fungi have chitin, bacteria have peptidoglycan, and algae have cellulose.

🎯 Exam Tip: It's important to remember the unique cell wall compositions, as they are key identifying features for these organism groups.

Question 17. What is meant by Holocentric chromosomes?
Answer: If a chromosome has centromere activity distributed along its entire surface during mitosis, it is called a holocentric chromosome. This means microtubules are distributed all along the mitotic chromosome. For example, Caenorhabditis Elegans (a type of transparent nematode) and many insects have holocentric chromosomes. They do not have a single, localized centromere.
In simple words: A holocentric chromosome is one where the pulling forces during cell division are spread out along its whole length, not just at one central spot.

🎯 Exam Tip: When defining holocentric chromosomes, highlight that the centromere function is diffused along the entire chromosome, unlike in monocentric chromosomes.

Question 18. Differentiate between point centromere & Regional centromere.
Answer:

In simple words: Point centromeres are small and specific, binding one microtubule, like in yeast. Regional centromeres are larger, binding many microtubules, found in humans and other organisms.

🎯 Exam Tip: Focus on the size/specificity of the DNA sequence involved and the number of microtubules bound when differentiating between point and regional centromeres.

Question 19. Draw the structure of the polytene chromosome:
Answer: A polytene chromosome is a large chromosome that forms when many rounds of DNA replication occur without cell division, creating multiple identical DNA strands aligned together. These chromosomes show distinct light and dark bands under a microscope.
In simple words: Polytene chromosomes are extra large chromosomes that have distinct dark and light stripes, formed by many copies of DNA stuck together.

🎯 Exam Tip: For polytene chromosomes, ensure your diagram clearly shows the alternating dark and light bands, and if possible, indicate a chromosomal puff, which represents areas of active gene expression.

Three Mark Questions

Question 1. Distinguish between autosomes & allosomes.
Answer:

In simple words: Autosomes are body chromosomes that decide most of your traits, while allosomes are sex chromosomes that decide if you are male or female.

🎯 Exam Tip: When distinguishing between autosomes and allosomes, clearly state their primary function: autosomes for somatic traits, allosomes for sex determination.

Question 2. Explain lampbrush chromosomes:
Answer: Lampbrush chromosomes are very large chromosomes with many DNA loops, first observed by Flemming in 1882 in the oocytes of salamanders and in the giant nucleus of unicellular algae Acetabularia. These highly condensed chromosomes form a central axis with lateral DNA loops, which are active sites for intense RNA synthesis. They get their name because their structure resembles a brush used for cleaning old lamp chimneys. This structure allows for a high rate of gene expression.
In simple words: Lampbrush chromosomes are very big chromosomes with many loops sticking out, seen in some animal egg cells. These loops are busy making RNA, which is needed to make proteins.

🎯 Exam Tip: When describing lampbrush chromosomes, emphasize their large size, the presence of lateral loops, and their role in active RNA synthesis, particularly in oocytes.

Question 3. Define cytoplasmic streaming.
Answer: Cytoplasmic streaming, also known as cyclosis, is the movement of the cytoplasm within a plant or animal cell, along with the cellular materials inside it. This continuous movement helps to circulate nutrients, organelles, and other substances throughout the cell, making sure everything is evenly distributed. It's especially important in large cells where simple diffusion would be too slow.
In simple words: Cytoplasmic streaming is when the jelly-like substance inside a cell moves around, carrying all the cell's parts and nutrients with it.

🎯 Exam Tip: Define cytoplasmic streaming as the movement of cytoplasm and cell contents, and mention its key role in nutrient and organelle distribution.

Question 4. Draw the structure of the Eukaryotic flagellum.
Answer: A eukaryotic flagellum is a whip-like structure on the outside of some cells that helps them move. It contains a central core called the axoneme, which has a specific arrangement of microtubules. These are short cellular projections bound by the plasma membrane.
In simple words: A eukaryotic flagellum is like a long tail that helps a cell move. Inside, it has many tiny tubes arranged in a special "9+2" pattern, with nine pairs around the edge and two in the middle.

🎯 Exam Tip: When drawing a eukaryotic flagellum, the most crucial detail is the "9+2" arrangement of microtubules in the axoneme. Clearly label the plasma membrane, outer microtubule doublets, central microtubules, and connecting structures like nexin and dynein arms.

Question 5. List out the functions of the Cell Wall.
Answer: The cell wall plays a vital role by performing several important functions:
1. It provides a definite shape and rigidity to the cell, helping it maintain its form.
2. It acts as a barrier, preventing several large molecules from entering the cells.
3. It protects the internal protoplasm from mechanical injury.
4. It prevents the bursting of cells by maintaining osmotic pressure.
5. It plays a major role by acting as a mechanism of defense for the cells, protecting against pathogens.
In simple words: The cell wall gives the cell its shape, keeps it strong, stops big things from getting in, protects the inside, and stops the cell from bursting. It also acts like a shield.

🎯 Exam Tip: Remember to include both structural (shape, rigidity, protection) and functional (barrier, osmotic pressure regulation, defense) roles of the cell wall for a complete answer.

Question 6. Explain in detail about Fluid mosaic model.
Answer: Jonathan Singer and Garth Nicolson (1972) proposed the fluid mosaic model. This model states that the cell membrane is made up of lipids and proteins, with a small amount of carbohydrates. The lipid membrane is primarily made of phospholipids, which have a hydrophobic (water-repelling) tail and a hydrophilic (water-loving) head. The hydrophobic tails keep water out. The proteins in the membrane are globular; some are integral (embedded within the lipid bilayer), and some are peripheral (attached to the surface). These proteins help transport molecules across the membrane and act as enzymes, receptors, or antigens. This dynamic structure allows for flexibility and various functions.
In simple words: The fluid mosaic model says the cell membrane is like a fluid (always moving) and a mosaic (made of different parts). It has a double layer of fats with proteins floating in or sticking to it, allowing the cell to control what goes in and out and to communicate.

🎯 Exam Tip: When explaining the fluid mosaic model, highlight the "fluid" nature (movement of components) and the "mosaic" aspect (diverse lipids, integral, and peripheral proteins), and briefly mention the roles of each component.

Question 7. Draw the structure of the chromosome & neatly label the parts.
Answer: A chromosome is a thread-like structure of nucleic acids and protein found in the nucleus of most living cells. It carries genetic information in the form of genes. Each chromosome at the beginning of cell division consists of two identical sister chromatids, connected at a centromere. The diagram below shows these parts.
In simple words: A chromosome is like a packed suitcase of DNA. It has two identical halves (chromatids) joined in the middle (centromere), and each half has a short 'p' arm and a long 'q' arm.

🎯 Exam Tip: Ensure your chromosome diagram clearly shows the two sister chromatids, the centromere, and the p and q arms. These labels are essential for full marks.

Question 8. Based on the position of centromere classify the chromosomes with the help of diagrams.
Answer: Chromosomes are classified into four types based on the position of their centromere:
1. **Metacentric:** Centromere is in the middle, resulting in two equal arms.
2. **Sub-metacentric:** Centromere is slightly off-center, making one arm shorter than the other.
3. **Acrocentric:** Centromere is near one end, with a very short 'p' arm and a long 'q' arm.
4. **Telocentric:** Centromere is at the very end, so there is only one arm.
Eukaryotic chromosomes can be rod-shaped (telo- and acrocentric) as well as meta- and sub-meta-centric.
In simple words: Chromosomes are grouped by where their centromere (the pinching point) is. It can be in the middle (metacentric), a bit off-center (sub-metacentric), near the end (acrocentric), or right at the end (telocentric), changing the shape of the chromosome arms.

🎯 Exam Tip: When classifying chromosomes, clearly define each type based on the centromere's position and the relative lengths of the arms. Visual aids are very helpful here.

Question 9. List out the functions of Golgi bodies.
Answer: The Golgi bodies perform several important functions:
1. They produce glycoproteins and glycolipids.
2. They are involved in transporting and storing lipids.
3. They play a role in the formation of lysosomes, which are waste disposal units of the cell.
4. They are responsible for the production of digestive enzymes.
5. They are crucial for cell plate and cell wall formation during cell division in plant cells.
6. They secrete carbohydrates needed for forming plant cell walls and insect cuticles.
7. They synthesize zymogen granules, which are proenzymes or precursors of all enzymes.
In simple words: Golgi bodies act like a cell's post office, making and packaging proteins and fats. They also create lysosomes, help build cell walls, and produce enzymes for digestion.

🎯 Exam Tip: Remember that Golgi bodies are central to modification, packaging, and secretion, as well as the formation of specific organelles and cell components.

Question 10. Distinguish between Resolution & Magnification:
Answer:

In simple words: Magnification makes things look bigger, while resolution helps us see tiny details clearly and separately. High magnification without good resolution just gives a blurry, big image.

🎯 Exam Tip: Differentiate resolution (clarity, ability to distinguish two points) from magnification (making an image larger). Both are crucial for effective microscopy, but they are not the same.

Question 11. Write in detail about the 3 types of centromere in eukaryotes.
Answer: There are three types of centromere in Eukaryotes, each with distinct features regarding kinetochore assembly and microtubule binding:
1. **Point Centromere:** In this type, the kinetochore is formed when specific protein recognizes specific DNA sequences. Kinetochores assembled on a point centromere bind a single microtubule. This is also called a localized centromere and is observed in organisms like budding yeasts.
2. **Regional Centromere:** In regional centromeres, the kinetochore is assembled on a variable array of repeated DNA sequences. Kinetochores assembled on regional centromeres bind multiple microtubules. This type of centromere is found in organisms such as fission yeast cells and humans.
3. **Holocentromere:** Here, the microtubules bind all along the mitotic chromosome, not just at one specific point. This means that centromere activity is distributed across the entire surface of the chromosome. This type is observed in organisms like Caenorhabditis Elegans (a transparent nematode) and many insects. This distributed binding ensures even segregation during cell division.
In simple words: Eukaryotic cells have three main types of centromeres: point centromeres (small, single microtubule), regional centromeres (larger, multiple microtubules), and holocentromeres (microtubules attach along the entire chromosome).

🎯 Exam Tip: For each type of centromere, remember to describe how the kinetochore is assembled, how many microtubules it binds, and a representative organism where it is found.

Question 12. Distinguish between primary wall & secondary wall of the plant cell wall.
Answer:

In simple words: The primary cell wall is the first, thin, and stretchy layer that lets a plant cell grow. The secondary cell wall grows inside it later, making the cell thick, strong, and rigid for support.

🎯 Exam Tip: Focus on the timing of formation, flexibility, thickness, and primary components to differentiate between primary and secondary cell walls. Highlight that primary walls are for growth, secondary for strength.

Question 13. Describe the steps involved in cytological techniques.
Answer: Cytological techniques involve various methods for preparing specimens for microscopic observation. The different types of mounting depend on the part of the specimen to be observed:
1. **Whole-mount:** The entire organism or a smaller structure is mounted directly onto a slide and observed. This method is useful for viewing intact, small specimens.
2. **Squash:** This preparation involves crushing or squashing the material onto a slide to reveal its internal contents. For example, pollen grains or root tips are squashed to observe chromosomes during mitosis and meiosis.
3. **Smears:** Here, the specimen, typically in a fluid (like blood or microbial cultures), is spread thinly across a slide. Cells are scraped, brushed, or aspirated from the surface of an organ. Epithelial cells can be observed using this method.
4. **Sections:** In this technique, freehand sections from a specimen, or thin sections prepared using a microtome, are selected, stained, and then mounted on a slide. This is common for observing the internal structure of plant parts like leaves and stems.
In simple words: Cytological techniques are ways to get cells ready to look at under a microscope. This can involve putting whole small things on a slide, squashing them, spreading them as a thin smear, or cutting very thin slices (sections).

🎯 Exam Tip: When describing cytological techniques, list the main methods (whole-mount, squash, smear, section) and briefly explain the purpose and a common example for each.

Question 14. List out any 3 stains used in histo-chemistry.
Answer: Here are some common stains used in histochemistry:

In simple words: To see different parts of cells, scientists use special dyes called stains. Eosin makes cytoplasm pink, Methylene blue makes the nucleus blue, and Saffranine makes the cell wall red. These stains help us see tiny cell structures clearly.

🎯 Exam Tip: When listing stains, mention the stain's name, the color it imparts, and what specific cell component it stains. Knowing these details is key for practical histology questions.

Question 15. Identify the diagram and label the parts.
Answer: This diagram represents a dark field microscope. It is a type of light microscope that uses a special condenser to block out most of the light, making the background dark and the specimen appear bright against it. This method is useful for observing live, unstained specimens.
In simple words: This picture shows a dark field microscope. It uses a special trick to make the background dark, so tiny things you want to see look bright against it, like stars in the night sky.

🎯 Exam Tip: When identifying and labeling a microscope diagram, ensure you correctly pinpoint the light source, condenser, stage, and objective lens. For a dark field microscope, specifically mention the patch stop in the condenser.

Five Mark Questions

Question 1. Differentiate between BFM & DFM.
Answer:

In simple words: A Bright Field Microscope (BFM) is the common one, showing specimens against a bright background, often needing stains. A Dark Field Microscope (DFM) makes the background dark and the specimen bright, which is great for seeing tiny, live, unstained things, but is used less often.

🎯 Exam Tip: When comparing BFM and DFM, focus on the background (bright vs. dark), the need for staining, and the type of condenser or light path used in each.

Question 2. Differentiate between Light microscope & Electron microscope.
Answer:

In simple words: Light microscopes use light to make objects bigger, good for schools, but don't show tiny details. Electron microscopes use electrons, can magnify much more, and show super fine details, used for advanced research.

🎯 Exam Tip: Highlight the fundamental difference in the source of illumination (light vs. electrons), which dictates their resolving power, magnification capabilities, and the types of specimens they can analyze.

Question 3. Write down the functions of the cell wall.
Answer: The cell wall serves several vital functions:

In simple words: The cell wall provides a strong, fixed shape, protects the cell from damage, controls what enters and exits, and stops the cell from bursting. This sturdy outer layer is key for plants to stand upright and resist environmental stresses.

🎯 Exam Tip: To score well, clearly list each function, like protection, shape maintenance, and osmotic regulation, as key roles of the cell wall.

Question 4. Write down the functions of the Plasma Membrane
Answer: The plasma membrane performs several important functions for the cell:

• The main job of the cell membrane is to move things in and out of the cell.
• It works like a channel, allowing molecules to pass through.
• The membrane chooses what goes in and out, meaning it's 'selectively permeable'.
• Things are moved across it in two main ways: processes that need energy, and processes that don't need energy, often using special proteins.
• For larger amounts of material, cells use endocytosis to bring things in and exocytosis to push things out, handling both solids and liquids.
• One type of endocytosis is phagocytosis, where the membrane wraps around and swallows large particles, like how some cells eat.

In simple words: The plasma membrane controls what goes in and out of the cell. It acts as a selective barrier and helps transport substances, including large particles, in and out. This membrane is crucial for maintaining the cell's internal environment, acting as its gatekeeper.

🎯 Exam Tip: When explaining membrane functions, remember to mention selective permeability and active transport processes for a complete answer.

Question 5. Explain the fluid mosaic model of plasma membrane.
Answer: The fluid mosaic model was suggested by Jonathan Singer and Garth Nicolson in 1972. This model describes the plasma membrane as being made mainly of lipids (especially phospholipids), proteins, and a small amount of carbohydrates.

• I. Phospholipid: Phospholipids have two parts: a 'water-loving' (hydrophilic) head that faces outward, and a 'water-fearing' (hydrophobic) tail that faces inward. The hydrophilic heads are made of polar phosphate groups, and the hydrophobic tails are non-polar fatty acids.
• II. Proteins of membrane: Proteins are found scattered within the lipid layers. Some are 'integral proteins' which pass all the way through or are deeply embedded in the lipid bilayer. Other proteins, called 'peripheral proteins', are loosely attached to the surface of the membrane. These proteins help move molecules across the membrane, also act as enzymes (speeding up chemical reactions), and serve as receptors for signals or as antigens.
• III. Carbohydrates: These are typically found on the outer surface, often attached to lipids or proteins, forming the glycocalyx.

In simple words: The fluid mosaic model says the cell membrane is like a fluid sea of lipids with proteins floating in it, like a mosaic. Lipids and proteins can move around, making the membrane flexible. The 'fluid' part of the model refers to how the lipids and proteins can move around, while 'mosaic' describes their scattered, patch-like arrangement.

🎯 Exam Tip: Highlight that the model describes a dynamic arrangement of lipids and proteins, emphasizing the 'fluid' and 'mosaic' aspects for full marks.

Question 6. Give an account of the structure and function of mitochondria.
Answer: Mitochondria are vital organelles in cells, often called the 'powerhouses'.

Historical Background: Mitochondria were first seen by A. Kolliker in 1880. Altmann called them 'Bio-plasts' in 1894, and Benda gave them the name 'Mitochondria' in 1897.

Structure:

• Mitochondria are typically oval or rod-shaped and can change their form.
• They are enclosed by two membranes: an outer membrane which is smooth and allows many things to pass, and an inner membrane.
• Between the two membranes is an outer chamber. Inside the inner membrane is a jelly-like substance called the matrix.
• The inner membrane folds inwards to form structures called cristae. These cristae contain enzymes important for the Electron Transport System (ETS).
• The inner membrane also has F1 particles, each with a base, stem, and rounded head. The head contains ATP synthase, which helps make ATP.
• Mitochondria are made of about 73% protein, 30% lipids, and contain their own RNA, circular DNA, and 70S ribosomes.

Functions:

• Mitochondria are known as the 'powerhouses of the cell' because they generate most of the cell's supply of adenosine triphosphate (ATP), which is used as a source of chemical energy. This process is called oxidative phosphorylation.
• They also play a role in cellular respiration, breaking down glucose to release energy.

In simple words: Mitochondria are cell parts that create energy (ATP) for the cell. They have two membranes, with the inner one folded to make cristae, and they contain their own DNA. Mitochondria are unique because they have their own genetic material and ribosomes, allowing them to make some of their own proteins, like tiny semi-autonomous organs within the cell.

🎯 Exam Tip: Always include the double membrane structure, cristae, matrix, and their role in ATP production when describing mitochondria.

Question 7. Structure of chloroplast
Answer: The chloroplast is a very important organelle found in green plants.

• It is enclosed by two membranes, with a space between them.
• Inside the inner membrane is a jelly-like substance called the stroma.
• Within the stroma are flattened sacs called thylakoids, which are connected to each other.
• Each thylakoid has an internal space called the thylakoid lumen.
• These thylakoids are stacked up like coins, forming structures called grana (singular: granum).
• In the grana, light energy is captured and changed into chemical energy, leading to the creation of carbohydrates.
• Chloroplasts contain chlorophyll pigments, storage bodies called osmophilic granules, 70S ribosomes, circular DNA without histones, and RNA.
• The chloroplast's own genetic material contains codes for about 30 proteins. These proteins are used in photosynthesis, including parts of Photosystem I and II, cytochrome complexes, ATP synthase, and a subunit of the RUBISCO enzyme.

In simple words: Chloroplasts are the parts of plant cells that make food using sunlight. They have two covers, a jelly inside called stroma, and stacks of little sacs called grana where sunlight is captured. Chloroplasts are the primary sites of photosynthesis, the process that converts sunlight into food for plants and oxygen for life on Earth.

🎯 Exam Tip: For chloroplasts, clearly mention the double membrane, stroma, thylakoids, and grana, linking them to photosynthesis.

Question 8. Give an account of Ribosomes:
Answer: Ribosomes are small, essential organelles found in all living cells.

• Ribosomes were first observed by George Palade in 1953.
• Under an electron microscope, they appear as dense particles and are not surrounded by a membrane.
• Each ribosome is made of two round subunits: one large subunit and one small subunit, which come together to form a complete ribosome.
• Magnesium ions (\( \text{Mg}^{++} \)) are needed for these two subunits to join together properly.
• Ribosomes are formed through a process called biogenesis, involving new formation, self-replication, and often originating from the nucleolus.
• Their main job is to be the sites where proteins are made inside the cell.
• Ribosomes are composed of about 60% ribosomal RNA (rRNA) and 40% protein.

In simple words: Ribosomes are tiny cell parts that build proteins. They have two pieces that join together, and magnesium helps them connect. These tiny cellular machines are essential for all living cells, translating genetic instructions into functional proteins.

🎯 Exam Tip: Remember to state that ribosomes are composed of two subunits and are the primary sites for protein synthesis in the cell.

Question 9. Differentiate between chromoplast & leucoplast
Answer: Here are the differences between chromoplasts and leucoplasts:

In simple words: Chromoplasts give plants red, orange, or yellow colors, like in flowers and fruits. Leucoplasts are colorless and are used to store food like starch or oil in roots and seeds. These plastids highlight the specialized roles organelles play in different parts of a plant, from energy production to storage and reproduction.

🎯 Exam Tip: Focus on the key differences in color, pigment type, and primary function (coloration vs. storage) when differentiating these plastids.

Question 10. State any 3 functions of Lysosomes
Answer: Lysosomes are crucial organelles with several functions:

• Intracellular Digestion: Lysosomes break down food particles like carbohydrates, proteins, and fats inside the cell. This process is called intracellular digestion.
• Autophagy: They also recycle old or damaged cell parts, such as mitochondria and endoplasmic reticulum. This process, called autophagy, helps the cell stay healthy, especially during tough times.
• Autolysis: Lysosomes can cause the cell to self-destruct if it's badly damaged or infected. This 'autolysis' happens when their powerful enzymes are released, breaking down the cell from within.

In simple words: Lysosomes help the cell clean up by breaking down old food and damaged parts. They can even make a cell self-destruct if needed. Often called the 'suicide bags' of the cell, lysosomes play a critical role in cellular waste disposal and programmed cell death.

🎯 Exam Tip: When listing lysosome functions, emphasize their role in intracellular digestion, autophagy, and autolysis using clear terms.

Question 11. Explain the structure of Centrioles
Answer: Centrioles are small, cylindrical organelles found in animal cells and some lower plants.

• A centriole has a central hub, around which nine sets of three (triplet) peripheral fibrils are arranged. These fibrils are made of a protein called tubulin.
• This structure is known as the '9+0' pattern, meaning there are nine triplets around the edge and nothing in the center.
• Centrioles act as the base (basal body) for cilia and flagella. They are also important in forming spindle fibers during cell division.

In simple words: Centrioles are small, tube-shaped cell parts made of nine groups of three tiny tubes around a middle hub. They help build other cell parts like flagella and are very important when a cell divides. Centrioles are vital for cell division in animal cells, helping to organize the chromosomes and ensure they are evenly split between new cells.

🎯 Exam Tip: The '9+0' triplet microtubule arrangement and their role in forming basal bodies and spindle fibers are crucial points for centrioles.

Question 12. Differentiate between other inclusions of cells in Prokaryotes & Eukaryotes.
Answer: Cellular inclusions are non-living substances present in the cytoplasm. Here's how they differ in prokaryotes and eukaryotes:

In simple words: Cells store different kinds of materials inside them, like food or waste. Prokaryotes (simple cells) store things like phosphate or sulfur. Eukaryotes (complex cells) store starch, fats, proteins, and sometimes even crystals. These varied inclusions demonstrate how different cell types store energy, manage waste, and protect themselves based on their specific needs and environment.

🎯 Exam Tip: Ensure your differentiation for cellular inclusions highlights the distinct storage and secretion materials found in prokaryotes versus eukaryotes.

Question 13. Explain the structure of the Nucleus.
Answer: The nucleus is often called the 'control center' or 'CPU' of the cell. It is usually the largest organelle and manages all cell activities. It also stores the cell's hereditary information (DNA).

Shapes: Nuclei can be spherical, cuboidal, elliptical, or discoidal in shape.

Main Parts: The nucleus has four main parts:

I. Nuclear Envelope: This is a double membrane that surrounds the nucleus.

• a) Outer membrane: This membrane often has ribosomes attached, giving it a rough appearance, and is connected to the endoplasmic reticulum.
• It also has nuclear pores, which are openings that allow molecules like mRNA, ribosomal subunits, proteins, and other large molecules to move in and out of the nucleus. Each nuclear pore is surrounded by a circular structure called an annulus.
• b) Inner membrane: This membrane is smooth and lacks ribosomes. The space between the inner and outer membranes is called the perinuclear space.

II. Nucleoplasm: The nucleoplasm is a jelly-like substance inside the nucleus, which contains two main parts:

• a) Nucleoli: These are small, dense, spherical structures that can appear alone or in groups. Nucleoli contain the genes responsible for making ribosomal RNA (rRNA) and transfer RNA (tRNA).
• b) Chromatin network: This is an uncoiled, thread-like structure visible during interphase (when the cell is not dividing). It is made of DNA wrapped around histone proteins, along with a small amount of RNA. During cell division, this chromatin condenses to form visible chromosomes.

Chromatin Types: Chromatin can be found in two forms:

1. Euchromatin: This is the less tightly packed, lightly stained part of chromatin. It is actively involved in making RNA (transcription) and contains active genes.
2. Heterochromatin: This part is tightly packed and stains more intensely. It is generally not active in making mRNA (transcription) and remains condensed.

In simple words: The nucleus is like the cell's control room, holding all its genetic information (DNA). It has a double cover (nuclear envelope) with tiny holes for things to pass through. Inside is a jelly (nucleoplasm) which contains the nucleolus (where ribosomes are made) and chromatin (the DNA material that forms chromosomes). The intricate structure of the nucleus ensures that the cell's genetic material is protected, organized, and accurately expressed, guiding all cellular processes.

🎯 Exam Tip: For the nucleus, describe its envelope, nucleoplasm, nucleolus, and chromatin, emphasizing its role in genetic control.

Question 14. Explain the structure of Endoplasmic reticulum
Answer: The Endoplasmic Reticulum (ER) is the largest internal membrane system within a cell, named by K.R. Porter in 1948.

Structure: It is made up of three main parts:

• Cisternae: These are long, broad, and flattened sac-like structures arranged in parallel stacks, forming lamellae. The space between these membranes is filled with fluid.
• Vesicles: These are small, oval, membrane-bound sacs.
• Tubules: These are irregularly shaped, branched, and smooth-walled structures that enclose a space.

Functions:

• The ER is connected to both the nuclear membrane and the cell's outer plasma membrane.
• When ribosomes are attached to the ER surface, it is called the Rough Endoplasmic Reticulum (RER). The RER is involved in protein synthesis and modification.
• When no ribosomes are present, it is known as the Smooth Endoplasmic Reticulum (SER). The SER is involved in lipid synthesis, detoxification, and calcium storage.

In simple words: The Endoplasmic Reticulum (ER) is like a network of membranes inside the cell. It has flat sacs (cisternae), small bags (vesicles), and tubes (tubules). If it has ribosomes, it's rough ER and makes proteins. If it doesn't have ribosomes, it's smooth ER and makes fats. The ER acts like an internal cellular highway system, transporting and processing molecules throughout the cell, and is vital for many metabolic processes.

🎯 Exam Tip: Describe the ER's network of cisternae, tubules, and vesicles, distinguishing between RER and SER functions for a complete answer.