Section l

1. Choose the correct option.

SECTION I: Choose the correct option.

1. Which of the following is a single-celled organism?
   a. Bacteria
   b. Amoeba
   c. Yeast
   d. All of these
   Answer: d. All of these

2. Members-bound bodies found in the cytoplasm of a cell and performing definite functions.
   a. Cell membrane
   b. Cell wall
   c. Plasma membrane
   d. Cell organelles
   Answer: d. Cell organelles

3. The nucleus consists of all the following except the ______.
   a. Nucleoplasm
   b. Chromosome
   c. Centrosome
   d. Nucleolus 
   Answer: c. Centrosome

4. The shape of a plant cell is ______.
   a. Axa
   b. Spherical
   c. Geometrical
   d. Irregular
   Answer: c. Geometrical (typically rectangular/box-like due to cell wall)

5. The structure present in animal cells but not in plant cells is ______.
   a. Golgi body
   b. Vacuole
   c. Ribosome
   d. Centrosome
   Answer: d. Centrosome (plant cells lack centrioles)

6. Which of the following is a type of plastid?
   a. Chromoplast
   b. Protoplast
   c. Leucoplast
   d. Chloroplast
   e. Only S (irrelevant option)
   Answer: a, c, d (Chromoplast, Leucoplast, Chloroplast are plastids; “Protoplast” is a cell without a wall.)

7. The supportive framework of the cell is ______.
   a. REP
   b. Golgi body
   c. Cytoplasm
   d. Organelles
   Answer: (Question unclear; likely “cytoskeleton,” but not listed. Possible typo in options.)

8. A student observed flat shape, central nucleus, and cell membrane. Which cell was it?
   a. Onion peel cells
   b. Amoeba
   c. Bacteria
   d. Cheek cells
   Answer: d. Cheek cells (human epithelial cells match the description)

9. The hereditary units that decide parental traits are called ______.
   a. Chloroplast
   b. Chromosomes
   c. Genes
   d. Centrosomes
   Answer: c. Genes (located on chromosomes but are the functional units)

10. To which cell can the shape of Amoeba be compared?
    a. Red blood cell
    b. White blood cell
    c. Skin cell
    d. Muscle cell
    Answer: b. White blood cell (both are irregular and can change shape)
11. Assertion and Reasoning Questions
12. Assertion (A): All cells arise from the pre-existing cells.
    Reason (R): Cells can undergo cell division.
13. Both A and R are True. b. Both A and R are false. c. A is true and R is false. d. A is false and R is true.

      Answer: a. Both A and R are True. (A aligns with the cell theory;   R explains how pre-existing cells multiply.)

2. Assertion (A): Centrosomes are organelles containing two centrioles.
   Reason (R): Centrosomes are found both in plant cells and animal cells.

Both A and R are True. b. Both A and R are false. c. A is true and R is false. d. A is false and R is true.

Answer: c. A is True and R is False. (Centrosomes with centrioles are absent in most plant cells.)

c.Name the following.

Name the Following

1. The protective covering of plant cells
   • Answer: Cell wall
2. Granular structures that either exist freely in the cytoplasm or are attached to the endoplasmic reticulum
   • Answer: Ribosomes
3. The cell organelle also called the ‘powerhouse of a cell’
   • Answer: Mitochondria
4. Membrane-bound sacs in the cytoplasm of animal cells that contain digestive enzymes
   • Answer: Lysosomes
5. Colourless plastids
   • Answer: Leucoplasts

D. Choose the Odd One Out

1. Bacteria, Amoeba, Neuron, Yeast

Answer: Neuron (Only multicellular organism; others are unicellular.)

2. Centrosome, Chloroplast, Central nucleus, Lysosome

Answer: Chloroplast (Only found in plant cells; others are in animal cells.)

3. Nucleolus, Chromatin, Nucellus, Nucleoplasm

Answer: Nucellus  (Part of an ovule in plants; others are nuclear components.)

4. Leaf cell, Skin cell, Nerve cell, RBC

Answer: Leaf cell (Plant cell; others are animal cells.)

5. Lysosome, Chromosome, Centrosome, Ribosome

Answer: Chromosome (Genetic material; others are organelles.)

Match the Columns

Column A	Column B (Answer)
1. Protoplasm	a. Brain cell
2. Mitochondria	b. Suicidal bag
3. Leucoplast	c. Powerhouse of the cell
4. Lysosome	d. Life-giving substance
5. Nucleus	e. Imparts colour
	f. Make food
	g. Store food

Column A	Column B (Answer)
1. Protoplasm	d. Life-giving substance
2. Mitochondria	c. Powerhouse of cell
3. Leucoplast	g. Store food
4. Lysosome	b. Suicidal bag
5. Nucleus	a. Brain cell (Control center)

F. True/False (Correct the False Statements)

1. Plant cells have different shapes.
   • Answer: T
2. The cell membrane is freely permeable.
   • Answer: F → “Selectively permeable”
3. The longest cell is that of an ostrich egg.
   • Answer: F → “Nerve cell” (Ostrich egg is largest, not longest.)
4. The colours imparted by chromoplasts promote pollination.
   • Answer: T
5. Centrosomes help in cell division.
   • Answer: T (Organize spindle fibers in animal cells.)

G. Complete the passage below by filling in the blank spaces.

The (1) Nucleus is the controlling centre of the cell, and hence it is called the (2) Brain of the cell.  It contains a network of thread–like structures called (3) Chromatin that contains the hereditary units, known as (4) genes. During cell division, the chromatin fibres condense to form the (5) chromosomes

H. State the exact location and function of the following.

1. Cytoplasm .2. Cell wall.3 Endoplasmic Reticulum. 4. Chlorophyll 5. Ribosome.

1. Cytoplasm

Location: Found inside the cell membrane (in both plant and animal cells) but outside the nucleus.
Function: The cytoplasm is a gel-like substance that houses all cell organelles (e.g., mitochondria, ribosomes). It facilitates:

• Metabolic Reactions: Enzymes in the cytoplasm drive processes like glycolysis.
• Transport: Moves nutrients and organelles via cytoplasmic streaming (cyclosis).
• Structural Support: Maintains cell shape and suspends organelles.

2. Cell Wall

Location: Outer layer of plant, fungal, and bacterial cells (absent in animals).
Function: Provides:

• Rigidity & Shape: Made of cellulose (plants) or chitin (fungi).
• Protection: Shields against mechanical stress and pathogens.
• Prevents Bursting: Resists osmotic pressure in hypotonic environments.

3. Endoplasmic Reticulum (ER)

Location: Network extending from the nuclear membrane throughout the cytoplasm.
Function: Two types:

• Rough ER: Ribosome-studded; synthesizes and transports proteins.
• Smooth ER: Lipid synthesis, detoxification (liver cells), and calcium storage (muscle cells).

4. Chlorophyll

Location: Embedded in thylakoid membranes of chloroplasts (plant cells).
Function:

• Photosynthesis: Absorbs sunlight (blue/red wavelengths) to convert CO₂ + H₂O into glucose.
• Pigmentation: Imparts green color to leaves.

Magnesium (Mg²⁺) is the central atom in its structure.

5. Ribosome

Location: Free-floating in cytoplasm or attached to rough ER/nuclear envelope.
Function:

• Protein Synthesis: Reads mRNA to assemble amino acids into polypeptides.
• “Protein Factories”: Critical for enzyme, hormone, and structural protein production.

Composed of rRNA (60%) and proteins (40%).

l.. Give reason for the following.

1. Red blood cells are biconcave and disc-like in shape.

Answer. Red Blood Cells (RBCs) Are Biconcave and Disc-Like in Shape

Red blood cells (erythrocytes) have a unique biconcave disc shape to optimize their function:

• Increased Surface Area: The flattened, indented shape maximizes surface area for efficient oxygen and carbon dioxide exchange.
• Flexibility: Allows RBCs to squeeze through narrow capillaries (as small as 3–4 μm) without damage.
• Optimal Diffusion: The thin center ensures gases diffuse quickly across the membrane.

Disruption: Genetic disorders like sickle cell anemia alter this shape, impairing oxygen transport.

2. The nucleus is called the brain of the cell.

Answer.  The Nucleus Is Called the Brain of the Cell

The nucleus controls cellular activities, mirroring the brain’s role:

• Genetic Blueprint: Stores DNA, which directs protein synthesis and regulates cell functions.
• Cell Division: Orchestrates mitosis/meiosis via chromosomes.
• Response to Signals: Nucleolus produces ribosomes for protein synthesis based on cellular needs.

Example: Enucleated (nucleus-removed) cells like mature RBCs survive briefly but cannot repair or replicate.

3. Mitochondria are known as the powerhouse of a cell.

Answer.Mitochondria Are Known as the Powerhouse of the Cell

Mitochondria generate ATP (adenosine triphosphate), the cell’s energy currency:

• Cellular Respiration: Convert glucose (from food) into ATP via oxidative phosphorylation.
• High-Energy Demand: Abundant in muscle/liver cells for sustained activity.
• Self-Replication: Contain their own DNA (mtDNA), suggesting evolutionary symbiosis.

Disorder: Mitochondrial dysfunction causes fatigue (e.g., Leigh syndrome).

4. A cell will die if the nucleus is removed from it.

Answer. A Cell Dies If the Nucleus Is Removed

The nucleus is indispensable for survival:

• DNA Dependency: Without DNA, cells cannot synthesize proteins or enzymes for metabolism.
• No Replication: Loses ability to divide (critical for growth/repair).
• Short Lifespan: Enucleated cells (e.g., mature RBCs) lack repair mechanisms and die in ~120 days.

Exception: Some cells (e.g., platelets) function without nuclei but are fragments of larger cells.

5. Leavers are green in colour.

Answer. Leaves Are Green in Colour

Leaves appear green due to chlorophyll, the pigment essential for photosynthesis:

• Light Absorption: Chlorophyll absorbs blue/red light (for energy) but reflects green, giving leaves their color.
• Seasonal Change: In autumn, chlorophyll breaks down, revealing yellow/orange carotenoids.

Adaptation: Plants in low light may produce more chlorophyll to maximize energy capture.

J. Differentiate between the following

1. Unicellular organisms and multicellular organisms.

2. Cell wall and cell membrane

3. Chromosomes and centrosome

4. Lysosome and Vacuole

5. Mitochondria and Chloroplasts.

1. Unicellular vs. Multicellular Organisms

Feature	Unicellular Organisms	Multicellular Organisms
Definition	Made of a single cell.	Made of many cells.
Size	Microscopic (e.g., Amoeba).	Macroscopic (e.g., Humans).
Complexity	Simple structure.	Complex with specialized tissues/organs.
Lifespan	Short (hours to days).	Long (years to decades).
Reproduction	Asexual (binary fission, budding).	Sexual/asexual (mitosis, meiosis).
Cell Differentiation	None; one cell performs all functions.	Cells specialize (e.g., nerve, muscle cells).
Examples	Bacteria, Paramecium, Yeast.	Plants, animals, fungi.
Metabolism	Limited efficiency.	High efficiency due to division of labor.
Adaptability	Less adaptable to environmental changes.	More adaptable (e.g., immune system).
Energy Needs	Low energy requirements.	High energy demands.

2. Cell Wall vs. Cell Membrane

Feature	Cell Wall	Cell Membrane
Presence	Found in plants, fungi, bacteria.	Present in all cells.
Composition	Made of cellulose (plants), chitin (fungi).	Phospholipid bilayer with proteins.
Permeability	Fully permeable.	Selectively permeable.
Flexibility	Rigid and inflexible.	Flexible and fluid.
Function	Provides shape, protection, and support.	Regulates entry/exit of substances.
Thickness	Thick (0.1–10 μm).	Thin (7–10 nm).
Repairability	Cannot self-repair; synthesized anew.	Can self-repair (e.g., lipid bilayer fusion).
Locomotion	Hinders movement (fixed shape).	Allows cell movement (e.g., amoeboid motion).
Sensitivity	Insensitive to external signals.	Contains receptors for signaling.
Examples	Plant cells (rigid), bacterial cells.	Animal cells (no wall), protozoa.

3. Chromosomes vs. Centrosome

Feature	Chromosomes	Centrosome
Composition	DNA + histone proteins.	Two centrioles + pericentriolar material.
Function	Carry genetic information.	Organizes spindle fibers for cell division.
Location	Inside the nucleus.	Near the nucleus (animal cells).
Visibility	Visible only during cell division.	Visible throughout the cell cycle.
Number	Species-specific (e.g., 46 in humans).	One pair per cell.
Role in Division	Separate into daughter cells.	Poles spindle fibers to pull chromosomes apart.
Presence	All eukaryotic cells.	Animal cells (absent in most plants).
Structure	Thread-like (chromatin) or condensed (X-shaped).	Barrel-shaped (centrioles).
Replication	Replicates during S phase.	Duplicates before mitosis.
Mutation Impact	Causes genetic disorders (e.g., Down syndrome).	Causes division errors (e.g., cancer).

4. Lysosome vs. Vacuole

Feature	Lysosome	Vacuole
Type of Cell	Primarily, animal cells.	Plant cells (large); animal cells (small).
Function	Digests waste, pathogens, and dead organelles.	Stores nutrients, water, and waste.
Enzymes	Contains hydrolytic enzymes (e.g., lipases).	Few or no digestive enzymes.
pH Level	Highly acidic (pH ~4.5–5.0).	Neutral or slightly acidic.
Formation	Buds off from the Golgi apparatus.	Forms from ER and Golgi.
Size	Small (0.1–1.2 μm).	Large in plants (up to 90% cell volume).
Content	Degradative molecules.	Water, ions, pigments (e.g., anthocyanins).
Role in Death	Causes autolysis (cell suicide).	Maintains turgor pressure (plant rigidity).
Disease Link	Tay-Sachs (enzyme deficiency).	Wilting in plants (water loss).
Example	Macrophages digesting bacteria.	Central vacuole in plant cells.

5. Mitochondria vs. Chloroplasts

Feature	Mitochondria	Chloroplasts
Function	ATP production (cellular respiration).	Photosynthesis (glucose synthesis).
Organism Type	All eukaryotes (animals, plants, fungi).	Only in plants/algae.
Energy Source	Breaks down glucose.	Uses sunlight (light energy).
Pigments	None.	Chlorophyll (green), carotenoids.
Internal Structure	Cristae (folds) for ATP synthesis.	Thylakoids (grana stacks) for light capture.
Byproduct	CO₂ + H₂O.	O₂ + glucose.
DNA	Circular mtDNA (maternal inheritance).	Circular cpDNA.
Color	Colorless.	Green.
Evolution	Derived from aerobic bacteria (endosymbiosis).	Derived from cyanobacteria.
Disease Link	Mitochondrial disorders (e.g., MELAS).	Chlorosis (lack of chlorophyll).

k.  Short answer questions.

1. Who proposed the cell theory?

Answer. The cell theory, a cornerstone of biology, was formulated by Matthias Schleiden (1838) and Theodor Schwann (1839). Schleiden, a botanist, concluded that all plants are composed of cells, while Schwann, a zoologist, extended this idea to animals. Later, Rudolf Virchow (1855) added that all cells arise from pre-existing cells.

2. How was the term ‘Cell’ derived? Who proposed the term?

Answer. The term “cell” was coined by Robert Hooke in 1665. While examining cork under a primitive microscope, Hooke observed tiny, box-like compartments resembling monks’ quarters (“cells” in Latin). However, he only saw dead cell walls.

3. Define protoplasm.

Answer. Protoplasm refers to the living, jelly-like substance inside a cell, comprising:

• Cytoplasm: Gel-like matrix (organelles + cytosol).
• Nucleoplasm: Fluid within the nucleus (DNA + nucleolus).

Functions:

• Site of metabolic reactions (e.g., glycolysis).
• Medium for organelle movement and nutrient transport.

4. What is the function of the cell membrane?

Answer. The cell membrane (plasma membrane) is a phospholipid bilayer with embedded proteins. Its roles include:

1. Selective Permeability: Regulates entry/exit of substances (e.g., osmosis).
2. Cell Signaling: Receptor proteins detect hormones (e.g., insulin).
3. Structural Integrity: Maintains cell shape (with cytoskeleton).
4. Compartmentalization: Separates cytoplasm from extracellular fluid.

Example: Nutrient absorption in intestinal cells.

• Where are genes located, and what is their function?

Answer. Location: Genes are segments of DNA housed on chromosomes in the nucleus (or mitochondria/chloroplasts).

Functions:

1. Heredity: Transmit traits (e.g., eye color) via alleles.
2. Protein Synthesis: Encode instructions for polypeptides.
3. Regulation: Control gene expression (e.g., lac operon).

L. Long answer questions.

1. What does the cell theory state?

Answer. The cell theory is one of the most fundamental principles in biology, unifying our understanding of life at the microscopic level. Proposed in the 19th century, it has evolved but remains rooted in three core ideas, with later additions refining its scope. Below is a detailed explanation of its principles, historical context, and modern implications.

The Three Core Principles of Cell Theory

1. All Living Organisms Are Composed of Cells

Whether a single-celled bacterium or a complex multicellular organism like a human, all life is built from cells. Cells are the basic structural and functional units of life.

• Examples:
  • Unicellular organisms (e.g., Amoeba, Paramecium) perform all life processes within one cell.
  • Multicellular organisms (e.g., plants, animals) consist of trillions of specialized cells (e.g., muscle cells, neurons).

Exceptions?

• Viruses are not made of cells but rely on host cells to replicate, so they are not considered alive by this definition.

2. The Cell Is the Basic Unit of Life

Every biological function—metabolism, growth, reproduction, and response to stimuli—occurs at the cellular level.

• Key Functions of Cells:
  • Energy Production: Mitochondria generate ATP (energy currency).
  • Genetic Control: The nucleus houses DNA.
  • Protein Synthesis: Ribosomes build proteins.
  • Waste Management: Lysosomes break down cellular debris.

Why is this important?

Understanding diseases (e.g., cancer, diabetes) requires studying cellular dysfunction.

3. All Cells Arise from Pre-Existing Cells

Proposed by Rudolf Virchow (1855), this principle replaced the outdated idea of spontaneous generation (life arising from non-living matter).

• Evidence:
  • Cell Division: Mitosis (somatic cells) and meiosis (gametes) produce new cells.
  • Louis Pasteur’s Experiment (1861): Disproved spontaneous generation by showing microbes only grow from existing ones.

Exceptions?

• The first cell on Earth likely arose from abiogenesis (non-living chemicals), but this occurred billions of years ago.

Modern Additions to Cell Theory

While the original three principles remain central, advancements in biology have expanded the theory:

4. Cells Contain Hereditary Information (DNA)

• DNA is passed from the parent to daughter cells during division.
• Mutations in DNA can lead to diseases like cancer.

5. Energy Flow (Metabolism) Occurs Within Cells

• Photosynthesis (in chloroplasts) and cellular respiration (in mitochondria) sustain life.

6. All Cells Share a Common Biochemical Composition

• Despite diversity, cells universally contain:
  • Proteins, lipids, carbohydrates, nucleic acids.
  • Similar organelles (e.g., ribosomes in all life forms).

Historical Development of Cell Theory

Scientist	Contribution	Year
Robert Hooke	Coined the term “cell” after observing cork.	1665
Anton van Leeuwenhoek	First observed living cells (“animalcules”).	1674
Matthias Schleiden	Concluded plants are made of cells.	1838
Theodor Schwann	Extended cell theory to animals.	1839
Rudolf Virchow	Stated cells come from pre-existing cells.	1855

Importance of Cell Theory Today

1. Medical Research
   • Cancer studies focus on uncontrolled cell division.
   • Antibiotics target bacterial cells without harming human cells.
2. Biotechnology
   • Stem cell therapy relies on cell regeneration.
   • CRISPR gene editing modifies cellular DNA.
3. Evolutionary Biology
   • All life shares a common cellular ancestor (LUCA: Last Universal Common Ancestor).

2. Which organisms are more advanced – unicellular or multicellular? Give reasons in support of your answer.

Answer. The debate over whether unicellular (single-celled) or multicellular (many-celled) organisms are more “advanced” depends on how we define biological complexity, adaptability, and evolutionary success. While unicellular life dominates Earth in terms of sheer numbers and diversity, multicellular organisms exhibit greater specialization, longevity, and behavioral sophistication. Below, we explore the key differences and why multicellularity represents a more advanced form of life.

Defining “Advanced” in Biology

“Advanced” does not necessarily mean “better” but refers to:

• Structural complexity (tissues, organs, systems).
• Functional specialization (division of labor among cells).
• Adaptability (response to environmental changes).
• Long-term survival strategies (lifespan, reproduction).

By these criteria, multicellular organisms are more advanced, though unicellular life remains incredibly successful in its own right.

Why Multicellular Organisms Are More Advanced

1. Cellular Specialization (Division of Labor)

• Unicellular organisms (e.g., Amoeba, E. coli) perform all life processes (digestion, locomotion, reproduction) within a single cell.
• Multicellular organisms (e.g., humans, trees) have specialized cells:
  • Neurons transmit electrical signals.
  • Muscle cells contract for movement.
  • Red blood cells transport oxygen.

Why It Matters: Specialization increases efficiency. A human liver cell doesn’t need to photosynthesize; it focuses solely on detoxification.

2. Greater Size and Structural Complexity

• Unicellular organisms are microscopic (0.1–5 μm).
• Multicellular organisms can grow massively (e.g., blue whales, giant sequoias).
  • Allows for complex organs (brain, heart, roots).
  • Supports long-distance nutrient transport (circulatory system in animals, xylem in plants).

Example: The human brain contains ~86 billion neurons, enabling advanced cognition.

3. Enhanced Adaptability and Survival

• Unicellular organisms rely on rapid reproduction (e.g., bacteria divide every 20 minutes).
• Multicellular organisms develop:
  • Immune systems (white blood cells fight pathogens).
  • Nervous systems (rapid response to threats).
  • Repair mechanisms (stem cells regenerate tissues).

Example: A deer fleeing a predator uses muscles (movement), eyes (vision), and brain (decision-making)—all coordinated systems.

4. Longer Lifespans and Delayed Reproduction

• Unicellular lifespan: Minutes to days (some bacteria).
• Multicellular lifespan: Years to centuries (oak trees, humans, tortoises).
  • Allows for learning, memory, and social structures.

Exception: Some unicellular organisms form dormant spores to survive harsh conditions.

5. Evolutionary Innovation

• Multicellularity evolved at least 25 times independently (e.g., animals, plants, fungi).
• Enabled predator-prey dynamics, ecosystems, and biodiversity.

Example: Coral reefs (multicellular) support thousands of species, while bacterial mats do not.

Arguments for Unicellular Dominance

Despite multicellular advantages, unicellular life excels in:

1. Sheer Numbers: Bacteria make up ~13% of Earth’s biomass.
2. Extreme Survival: Archaea thrive in boiling vents or acidic pools.
3. Reproductive Speed: A single bacterium can produce millions in hours.

However, these traits reflect efficiency, not complexity.

Exceptions and Gray Areas

• Slime molds (e.g., Dictyostelium) switch between unicellular and multicellular states.
• Volvox (a green alga) bridges the gap—it’s a colony of cells with limited specialization.

3. Explain the structure of the nucleus with the help of a labelled diagram.

Answer.

4. What are plastids? Write an account on the different types of plastids found in plants.

Answer. Plastids are double-membrane-bound organelles found in plant cells and some protists (like algae). They are responsible for synthesis, storage, and pigment production, playing crucial roles in photosynthesis, nutrient storage, and cellular metabolism. Plastids are unique to plants and are derived from proplastids (undifferentiated precursors) in meristematic tissues.

Plastids contain their DNA (ptDNA) and ribosomes, suggesting an endosymbiotic origin from ancient photosynthetic bacteria. They are highly dynamic, capable of interconversion based on cellular needs.

Types of Plastids in Plants

Plastids are classified into three main types, each with distinct functions:

1. Chloroplasts (Green Plastids)

• Function: Perform photosynthesis—convert sunlight, CO₂, and water into glucose and oxygen.
• Pigment: Contains chlorophyll (green pigment) and accessory pigments (carotenoids).
• Structure:
  • Thylakoids: Membrane-bound discs (stacked into grana) where light reactions occur.
  • Stroma: Fluid-filled space where the Calvin cycle fixes CO₂ into sugars.
• Location: Abundant in leaves and young stems.
• Example: Spinach leaves appear green due to densely packed chloroplasts.

Special Feature: Chloroplasts can move within cells to optimize light absorption.

2. Chromoplasts (Colored Plastids, Non-Green)

• Function: Synthesize and store pigments that attract pollinators and seed dispersers.
• Pigments:
  • Carotenoids (orange, red, yellow) – e.g., carrots (β-carotene), tomatoes (lycopene).
  • Xanthophylls (yellow) – e.g., marigold flowers.
• Structure: Lacks chlorophyll but contains lipid droplets for pigment storage.
• Location: Found in flowers, fruits, and aging leaves.
• Example: The red color of ripe peppers comes from chromoplasts.

Role in Evolution: Chromoplasts likely evolved to enhance plant-animal interactions (pollination/fruit dispersal).

3. Leucoplasts (Colorless Plastids)

Leucoplasts are non-pigmented and function primarily in nutrient storage. They are further classified into:

(a) Amyloplasts (Starch Storage)

• Function: Store starch granules in roots, tubers, and seeds.
• Example: Potatoes contain amyloplasts that stockpile starch.

(b) Elaioplasts (Lipid Storage)

• Function: Store oils and fats.
• Example: Found in seeds of sunflowers and castor plants.

(c) Proteinoplasts (Protein Storage)

• Function: Accumulate proteins in seeds (e.g., beans, peas).

Special Feature: Leucoplasts can convert into chloroplasts when exposed to light (e.g., potato tubers turning green).

5. Draw a labelled diagram of a typical animal cell.

6. Differentiate between a plant cell and an animal cell.

Answer.

Feature	Plant Cell	Animal Cell
1. Cell Wall	Present (made of cellulose).	Absent.
2. Shape	Fixed(rectangular/geometric).	Irregular (round/spherical).
3. Vacuole	Large, central vacuole (stores water).	Small, temporary vacuoles.
4. Chloroplasts	Present (for photosynthesis).	Absent (no photosynthesis).
5. Plastids	Present (e.g., chromoplasts).	Absent.
6. Centrosomes	Absent (except in lower plants).	Present (organize spindle fibers).
7. Lysosomes	Rare (enzymes in vacuoles).	Common (digestive enzymes).
8. Glyoxysomes	Present (convert fat to sugar).	Absent.
9. Plasmodesmata	Present (cell junctions).	Absent (use gap junctions instead).
10. Storage	Stores starch.	Stores glycogen.
11. Mitochondria	Fewer (rely on chloroplasts).	More numerous (main energy source).
12. Nucleus Position	Pushed to the side by vacuole.	Centrally located.
13. Mobility	Immobile (fixed in place).	Mobile (can change shape/move).
14. Extracellular Matrix	No ECM (cell wall provides support).	Has ECM (collagen, fibronectin).
15. Turgor Pressure	Maintains rigidity (due to vacuole).	No turgor pressure (flexible).