🧬 The Fundamental Unit of Life – Class 9 Science MCQs

Section 4: Applications, Numericals & HOTS (Q76–Q100)

Q76. When raisins are kept in water, they swell up due to:

A. Diffusion
B. Osmosis
C. Active transport
D. Endocytosis

✅ Correct Answer: B. Osmosis

Explanation:

• A. Diffusion → Not specific to water.
• B. Correct, water enters raisins through osmosis.
• C. Active transport requires energy.
• D. Endocytosis → Engulfing, not relevant here.

Q77. When raisins are kept in strong sugar solution, they shrink because:

A. Endocytosis
B. Plasmolysis
C. Exocytosis
D. Active transport

✅ Correct Answer: B. Plasmolysis

Explanation:

• A. Engulfing → Wrong.
• B. Correct, water moves out → cell shrinks.
• C. Exocytosis → Not related.
• D. Wrong, no energy involved.

Q78. If a cell is placed in isotonic solution, water movement will be:

A. Into the cell only
B. Out of the cell only
C. Both into and out equally
D. No movement at all

✅ Correct Answer: C. Both into and out equally

Explanation:

• A. Only inward → Hypotonic.
• B. Only outward → Hypertonic.
• C. Correct, dynamic equilibrium.
• D. Wrong, molecules always move.

Q79. The process of engulfing food particles by a cell is:

A. Exocytosis
B. Phagocytosis
C. Pinocytosis
D. Plasmolysis

✅ Correct Answer: B. Phagocytosis

Explanation:

• A. Exocytosis → Expelling substances.
• B. Correct, phagocytosis = “cell eating.”
• C. Pinocytosis = “cell drinking.”
• D. Plasmolysis → Shrinking.

Q80. Amoeba engulfs food by:

A. Endocytosis
B. Exocytosis
C. Diffusion
D. Osmosis

✅ Correct Answer: A. Endocytosis

Explanation:

• A. Correct, pseudopodia help engulf food.
• B. Wrong, opposite process.
• C. Gas exchange, not food.
• D. Osmosis → Only water movement.

Q81. Which process requires energy?

A. Diffusion
B. Osmosis
C. Active transport
D. Facilitated diffusion

✅ Correct Answer: C. Active transport

Explanation:

• A. Diffusion → Passive.
• B. Osmosis → Passive.
• C. Correct, active transport uses ATP.
• D. Facilitated diffusion → Passive (helped by proteins).

Q82. Example of exocytosis is:

A. Secretion of hormones
B. Engulfing food by Amoeba
C. Entry of O₂ into cell
D. Shrinking of cell in salt solution

✅ Correct Answer: A. Secretion of hormones

Explanation:

• A. Correct, vesicles release hormones.
• B. Endocytosis.
• C. Diffusion.
• D. Plasmolysis.

Q83. The cell organelle involved in secretion of enzymes is:

A. Ribosome
B. Golgi body
C. Mitochondria
D. Vacuole

✅ Correct Answer: B. Golgi body

Explanation:

• A. Protein synthesis only.
• B. Correct, Golgi modifies & secretes enzymes.
• C. Respiration.
• D. Storage.

Q84. In a plant cell, loss of water leads to shrinking of cytoplasm from cell wall. This is called:

A. Exocytosis
B. Pinocytosis
C. Plasmolysis
D. Cytolysis

✅ Correct Answer: C. Plasmolysis

Explanation:

• A. Secretion.
• B. Cell drinking.
• C. Correct, water loss → cytoplasm shrinkage.
• D. Bursting, opposite.

Q85. Which organelle is called the “protein packaging factory”?

A. Ribosome
B. Golgi body
C. Lysosome
D. Vacuole

✅ Correct Answer: B. Golgi body

Explanation:

• A. Ribosome → Protein synthesis, not packaging.
• B. Correct, Golgi packages proteins.
• C. Digestion.
• D. Storage.

Q86. If a cell has no Golgi apparatus, it will fail to:

A. Respire
B. Synthesize proteins
C. Package and secrete proteins
D. Store waste

✅ Correct Answer: C. Package and secrete proteins

Explanation:

• A. Respiration → Mitochondria.
• B. Proteins → Ribosome.
• C. Correct.
• D. Storage → Vacuole.

Q87. The cell organelle involved in ATP synthesis is:

A. Ribosome
B. Mitochondria
C. Lysosome
D. Golgi

✅ Correct Answer: B. Mitochondria

Explanation:

• A. Proteins.
• B. Correct, mitochondria produce ATP.
• C. Digestion.
• D. Packaging.

Q88. Which of the following is absent in prokaryotic cells?

A. Plasma membrane
B. Mitochondria
C. Ribosome
D. Cytoplasm

✅ Correct Answer: B. Mitochondria

Explanation:

• A, C, D → Present.
• B. Correct, no membrane-bound organelles.

Q89. If a cell loses its mitochondria, it will fail to:

A. Divide
B. Synthesize proteins
C. Respire aerobically
D. Package enzymes

✅ Correct Answer: C. Respire aerobically

Explanation:

• A. Division → Nucleus.
• B. Proteins → Ribosome.
• C. Correct, mitochondria = powerhouse.
• D. Packaging → Golgi.

Q90. Which organelle provides turgidity to plant cells?

A. Ribosome
B. Vacuole
C. Lysosome
D. Nucleus

✅ Correct Answer: B. Vacuole

Explanation:

• A. Proteins.
• B. Correct, water-filled vacuole maintains turgor.
• C. Digestion.
• D. Control, not turgidity.

Q91. Why don’t animal cells burst in hypotonic solution?

A. They have thick cell wall
B. They have no vacuole
C. They regulate water by contractile vacuoles
D. They cannot absorb water

✅ Correct Answer: C. They regulate water by contractile vacuoles

Explanation:

• A. Cell wall → Only in plants.
• B. Small vacuole but not reason.
• C. Correct, contractile vacuoles expel excess water.
• D. Wrong, they can absorb.

Q92. Which organelle is called “cell’s post office”?

A. Ribosome
B. Golgi apparatus
C. Nucleus
D. Lysosome

✅ Correct Answer: B. Golgi apparatus

Explanation:

• A. Proteins.
• B. Correct, Golgi sorts, modifies, dispatches.
• C. Control.
• D. Digestion.

Q93. Which organelle controls cell division?

A. Mitochondria
B. Centrosome
C. Nucleus
D. Lysosome

✅ Correct Answer: B. Centrosome

Explanation:

• A. Respiration.
• B. Correct, centrosome forms spindle fibers.
• C. Controls activities, but division via centrosome.
• D. Wrong.

Q94. Which organelle forms spindle fibers during cell division?

A. Centrosome
B. Mitochondria
C. Golgi body
D. Ribosome

✅ Correct Answer: A. Centrosome

Explanation:

• A. Correct.
• B. Respiration.
• C. Packaging.
• D. Proteins.

Q95. Which organelle is abundant in pancreatic cells for enzyme secretion?

A. Lysosome
B. Rough ER
C. Smooth ER
D. Chloroplast

✅ Correct Answer: B. Rough ER

Explanation:

• A. Digestion, not secretion.
• B. Correct, RER produces secretory proteins.
• C. Lipids.
• D. Absent in animals.

Q96. Which process explains oxygen entering blood from lungs?

A. Osmosis
B. Diffusion
C. Active transport
D. Endocytosis

✅ Correct Answer: B. Diffusion

Explanation:

• A. Osmosis → Water only.
• B. Correct, gases diffuse from high to low concentration.
• C. Requires energy, not needed here.
• D. Wrong.

Q97. If RBCs are kept in pure water, they will:

A. Shrink
B. Burst
C. Remain same
D. Divide

✅ Correct Answer: B. Burst

Explanation:

• A. Shrink → Hypertonic.
• B. Correct, water enters by osmosis → hemolysis.
• C. Wrong, not isotonic.
• D. Wrong.

Q98. Why are lysosomes called “suicidal bags”?

A. They digest nutrients
B. They kill bacteria only
C. They release enzymes that can digest the cell itself
D. They are useless

✅ Correct Answer: C. They release enzymes that can digest the cell itself

Explanation:

• A. Not main reason.
• B. Partially true, but broader role.
• C. Correct, rupture causes self-digestion.
• D. Wrong.

Q99. Which organelle is semi-autonomous?

A. Ribosome
B. Lysosome
C. Mitochondria
D. Vacuole

✅ Correct Answer: C. Mitochondria

Explanation:

• A. Non-membrane, not autonomous.
• B. Single-membrane, dependent.
• C. Correct, own DNA & ribosomes.
• D. Storage only.

Q100. Which statement about the cell is true?

A. Animal cells have cell wall
B. Plant cells lack mitochondria
C. Both plant & animal cells have plasma membrane
D. Only plant cells have ribosomes

✅ Correct Answer: C. Both plant & animal cells have plasma membrane

Explanation:

• A. Wrong, animal cells lack cell wall.
• B. Wrong, both have mitochondria.
• C. Correct.
• D. Wrong, ribosomes in both.

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