Structure and Functions of the Cell

1. Which cell organelle is primarily responsible for sorting, packaging, and directing proteins to their final destinations?

A. Rough endoplasmic reticulum
B. Lysosome
C. Golgi apparatus
D. Peroxisome

Answer: C. Golgi apparatus

Explanation: The Golgi apparatus modifies, sorts, and packages proteins synthesized in the rough ER.

2. A cell actively synthesizing digestive enzymes is expected to have an abundance of:

A. Smooth ER and ribosomes
B. Rough ER and Golgi apparatus
C. Lysosomes and peroxisomes
D. Centrioles and microfilaments

Answer: B. Rough ER and Golgi apparatus

3. Which organelle contains hydrolytic enzymes capable of digesting worn-out cellular components?

A. Peroxisome
B. Golgi body
C. Lysosome
D. Nucleolus

Answer: C. Lysosome

4. The “powerhouse of the cell” is so called because it:

A. Stores genetic material
B. Produces ATP through oxidative phosphorylation
C. Synthesizes proteins
D. Digests foreign particles

Answer: B. Produces ATP through oxidative phosphorylation

5. Which organelle lacks a membrane?

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

Answer: C. Ribosome

6. Which of the following structures is present in prokaryotes but absent in eukaryotes?

A. Plasma membrane
B. Ribosomes
C. Membrane-bound nucleus
D. Cell wall of peptidoglycan

Answer: D. Cell wall of peptidoglycan

7. Which statement regarding mitochondria is INCORRECT?

A. They possess their own DNA.
B. They replicate independently.
C. They are involved in ATP synthesis.
D. They are synthesized de novo by the nucleus.

Answer: D. They are synthesized de novo by the nucleus.

8. Which cytoskeletal component is primarily responsible for chromosome movement during cell division?

A. Microfilaments
B. Intermediate filaments
C. Microtubules
D. Actin fibers

Answer: C. Microtubules

Transport Across Cell Membrane

9. Which process requires a carrier protein but does not require ATP?

A. Simple diffusion
B. Facilitated diffusion
C. Primary active transport
D. Endocytosis

Answer: B. Facilitated diffusion

10. Glucose enters erythrocytes mainly through:

A. Simple diffusion
B. Active transport
C. Facilitated diffusion
D. Pinocytosis

Answer: C. Facilitated diffusion

11. Which transport mechanism directly utilizes ATP hydrolysis?

A. Osmosis
B. Facilitated diffusion
C. Primary active transport
D. Filtration

Answer: C. Primary active transport

12. The Na⁺/K⁺-ATPase pump transports:

A. 2 Na⁺ out and 3 K⁺ in
B. 3 Na⁺ out and 2 K⁺ in
C. 3 Na⁺ in and 2 K⁺ out
D. 2 Na⁺ in and 3 K⁺ out

Answer: B. 3 Na⁺ out and 2 K⁺ in

13. Which process is most responsible for water movement across biological membranes?

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

Answer: C. Osmosis

14. Secondary active transport differs from primary active transport because it:

A. Does not involve proteins
B. Does not move solutes against gradient
C. Uses energy stored in ionic gradients
D. Requires direct ATP hydrolysis

Answer: C. Uses energy stored in ionic gradients

15. Absorption of glucose in the intestine via SGLT transporter is an example of:

A. Simple diffusion
B. Facilitated diffusion
C. Secondary active transport
D. Pinocytosis

Answer: C. Secondary active transport

16. Which of the following is an example of receptor-mediated endocytosis?

A. Phagocytosis of bacteria
B. Uptake of LDL cholesterol
C. Osmosis
D. Exocytosis

Answer: B. Uptake of LDL cholesterol

17. A red blood cell placed in a hypertonic solution will:

A. Swell and burst
B. Remain unchanged
C. Shrink due to water loss
D. Gain water

Answer: C. Shrink due to water loss

18. Which membrane component primarily determines membrane fluidity?

A. DNA
B. Cholesterol
C. Glycogen
D. RNA

Answer: B. Cholesterol

Cell Division

19. DNA replication occurs during:

A. G₁ phase
B. S phase
C. G₂ phase
D. M phase

Answer: B. S phase

20. During which phase of mitosis do chromosomes align at the equatorial plate?

A. Prophase
B. Metaphase
C. Anaphase
D. Telophase

Answer: B. Metaphase

21. Separation of sister chromatids occurs during:

A. Prophase
B. Metaphase
C. Anaphase
D. Telophase

Answer: C. Anaphase

22. Crossing over occurs during:

A. Prophase I of meiosis
B. Prophase II of meiosis
C. Metaphase I
D. Anaphase II

Answer: A. Prophase I of meiosis

23. The chromosome number is reduced by half during:

A. Mitosis
B. Cytokinesis
C. Meiosis I
D. Meiosis II

Answer: C. Meiosis I

24. Which phase is known as the “resting phase” although the cell is metabolically active?

A. M phase
B. Interphase
C. Telophase
D. Cytokinesis

Answer: B. Interphase

25. Failure of spindle fiber formation will directly prevent:

A. DNA replication
B. Protein synthesis
C. Chromosome segregation
D. ATP synthesis

Answer: C. Chromosome segregation

Cell Junctions

26. Which cell junction permits direct communication between adjacent cells?

A. Tight junction
B. Desmosome
C. Gap junction
D. Hemidesmosome

Answer: C. Gap junction

27. Tight junctions primarily function to:

A. Provide mechanical strength
B. Prevent passage of substances between cells
C. Allow ion exchange
D. Anchor cells to basement membrane

Answer: B. Prevent passage of substances between cells

28. Desmosomes are particularly abundant in tissues subjected to:

A. Secretion
B. Absorption
C. Mechanical stress
D. Cell division

Answer: C. Mechanical stress

29. Hemidesmosomes connect:

A. Cell to cell
B. Cell to extracellular matrix
C. Cytoplasm to nucleus
D. Mitochondria to ER

Answer: B. Cell to extracellular matrix

30. Which protein forms channels in gap junctions?

A. Cadherin
B. Integrin
C. Connexin
D. Actin

Answer: C. Connexin

Cell Communication and Signaling

31. Which signaling mechanism requires direct physical contact between signaling and target cells?

A. Endocrine
B. Paracrine
C. Contact-dependent
D. Synaptic

Answer: C. Contact-dependent

32. Neurotransmitter release at a neuromuscular junction is an example of:

A. Endocrine signaling
B. Synaptic signaling
C. Paracrine signaling
D. Autocrine signaling

Answer: B. Synaptic signaling

33. Hormones secreted by the thyroid gland act mainly through:

A. Contact-dependent signaling
B. Paracrine signaling
C. Endocrine signaling
D. Synaptic signaling

Answer: C. Endocrine signaling

34. Nitric oxide released from endothelial cells causing relaxation of nearby smooth muscle is an example of:

A. Endocrine signaling
B. Synaptic signaling
C. Contact-dependent signaling
D. Paracrine signaling

Answer: D. Paracrine signaling

35. Which signaling mode generally has the longest duration of action?

A. Contact-dependent
B. Synaptic
C. Endocrine
D. Paracrine

Answer: C. Endocrine

36. A signaling molecule acting on the same cell that secreted it exhibits:

A. Endocrine signaling
B. Synaptic signaling
C. Autocrine signaling
D. Contact-dependent signaling

Answer: C. Autocrine signaling

37. Which signaling mechanism is the fastest?

A. Endocrine
B. Paracrine
C. Synaptic
D. Contact-dependent

Answer: C. Synaptic

38. Insulin secreted by pancreatic β-cells reaches distant target tissues through:

A. Gap junctions
B. Synaptic transmission
C. Blood circulation
D. Direct cell contact

Answer: C. Blood circulation

39. Which of the following pairs is correctly matched?

A. Gap junction – Mechanical attachment
B. Desmosome – Intercellular communication
C. Tight junction – Barrier function
D. Hemidesmosome – Exchange of ions

Answer: C. Tight junction – Barrier function

40. A mutation affecting connexin proteins would most directly impair:

A. Endocrine signaling
B. Gap junction communication
C. Tight junction formation
D. Protein synthesis

Answer: B. Gap junction communication

Dr Alok Singh