BIOL 355 Molecular Cell Biology Exam Review | 2026/2027 |
Cell Structure, Protein Trafficking, Cell Cycle, Signaling & Gene
Regulation | Practice Questions & Answers
SECTION 1 — CELL STRUCTURE & ORGANIZATION
1. Which feature best distinguishes a eukaryotic cell from a
prokaryotic cell?
A. Presence of DNA
B. Presence of ribosomes
C. Presence of a membrane-bound nucleus
D. Presence of a plasma membrane
Correct Answer: C. Presence of a membrane-bound nucleus
Rationale: Eukaryotic cells contain a membrane-enclosed nucleus,
whereas prokaryotic cells lack a membrane-bound nucleus.
2. Which organelle is primarily responsible for ATP production through
oxidative phosphorylation?
A. Golgi apparatus
B. Mitochondrion
C. Lysosome
D. Peroxisome
Correct Answer: B. Mitochondrion
Rationale: Mitochondria generate most cellular ATP through the
electron transport chain and oxidative phosphorylation.
3. Which organelle contains hydrolytic enzymes used for intracellular
digestion?
,A. Lysosome
B. Nucleus
C. Ribosome
D. Centrosome
Correct Answer: A. Lysosome
Rationale: Lysosomes contain acid hydrolases that degrade
macromolecules delivered through endocytic, phagocytic, or
autophagic pathways.
4. Which organelle is the major site of protein synthesis?
A. Ribosome
B. Peroxisome
C. Lysosome
D. Golgi apparatus
Correct Answer: A. Ribosome
Rationale: Ribosomes translate messenger RNA into polypeptide
chains.
5. What is the primary function of the nucleolus?
A. Lipid synthesis
B. Ribosomal subunit production
C. ATP synthesis
D. DNA degradation
Correct Answer: B. Ribosomal subunit production
Rationale: The nucleolus synthesizes rRNA and assembles ribosomal
subunits.
6. Which organelle modifies, sorts, and packages many proteins?
,A. Golgi apparatus
B. Mitochondrion
C. Nucleus
D. Centrosome
Correct Answer: A. Golgi apparatus
Rationale: The Golgi modifies proteins and lipids and sorts them to
different cellular destinations.
7. Which cellular structure acts as the selective barrier between the
cytoplasm and extracellular environment?
A. Nuclear envelope
B. Plasma membrane
C. Cytoskeleton
D. Cell wall
Correct Answer: B. Plasma membrane
Rationale: The plasma membrane controls movement of substances
into and out of the cell.
8. Which cytoskeletal component is composed of tubulin?
A. Actin filament
B. Intermediate filament
C. Microtubule
D. Myosin filament
Correct Answer: C. Microtubule
Rationale: Microtubules are polymers of α- and β-tubulin heterodimers.
9. Which cytoskeletal component is especially important for resisting
mechanical stress?
, A. Intermediate filament
B. Microtubule
C. Actin filament
D. Septin only
Correct Answer: A. Intermediate filament
Rationale: Intermediate filaments provide tensile strength and
mechanical stability.
10. Which cytoskeletal polymer is directly involved in cell cortex
formation and many forms of cell migration?
A. Actin
B. Tubulin
C. Keratin only
D. Collagen
Correct Answer: A. Actin
Rationale: Actin filaments form the cortical cytoskeleton and participate
in protrusion, contraction, and migration.
11. What is the main function of the centrosome in animal cells?
A. Protein degradation
B. Microtubule organization
C. DNA replication
D. Lipid synthesis
Correct Answer: B. Microtubule organization
Rationale: The centrosome is a major microtubule-organizing center.
12. Which structure surrounds the nucleus?
Cell Structure, Protein Trafficking, Cell Cycle, Signaling & Gene
Regulation | Practice Questions & Answers
SECTION 1 — CELL STRUCTURE & ORGANIZATION
1. Which feature best distinguishes a eukaryotic cell from a
prokaryotic cell?
A. Presence of DNA
B. Presence of ribosomes
C. Presence of a membrane-bound nucleus
D. Presence of a plasma membrane
Correct Answer: C. Presence of a membrane-bound nucleus
Rationale: Eukaryotic cells contain a membrane-enclosed nucleus,
whereas prokaryotic cells lack a membrane-bound nucleus.
2. Which organelle is primarily responsible for ATP production through
oxidative phosphorylation?
A. Golgi apparatus
B. Mitochondrion
C. Lysosome
D. Peroxisome
Correct Answer: B. Mitochondrion
Rationale: Mitochondria generate most cellular ATP through the
electron transport chain and oxidative phosphorylation.
3. Which organelle contains hydrolytic enzymes used for intracellular
digestion?
,A. Lysosome
B. Nucleus
C. Ribosome
D. Centrosome
Correct Answer: A. Lysosome
Rationale: Lysosomes contain acid hydrolases that degrade
macromolecules delivered through endocytic, phagocytic, or
autophagic pathways.
4. Which organelle is the major site of protein synthesis?
A. Ribosome
B. Peroxisome
C. Lysosome
D. Golgi apparatus
Correct Answer: A. Ribosome
Rationale: Ribosomes translate messenger RNA into polypeptide
chains.
5. What is the primary function of the nucleolus?
A. Lipid synthesis
B. Ribosomal subunit production
C. ATP synthesis
D. DNA degradation
Correct Answer: B. Ribosomal subunit production
Rationale: The nucleolus synthesizes rRNA and assembles ribosomal
subunits.
6. Which organelle modifies, sorts, and packages many proteins?
,A. Golgi apparatus
B. Mitochondrion
C. Nucleus
D. Centrosome
Correct Answer: A. Golgi apparatus
Rationale: The Golgi modifies proteins and lipids and sorts them to
different cellular destinations.
7. Which cellular structure acts as the selective barrier between the
cytoplasm and extracellular environment?
A. Nuclear envelope
B. Plasma membrane
C. Cytoskeleton
D. Cell wall
Correct Answer: B. Plasma membrane
Rationale: The plasma membrane controls movement of substances
into and out of the cell.
8. Which cytoskeletal component is composed of tubulin?
A. Actin filament
B. Intermediate filament
C. Microtubule
D. Myosin filament
Correct Answer: C. Microtubule
Rationale: Microtubules are polymers of α- and β-tubulin heterodimers.
9. Which cytoskeletal component is especially important for resisting
mechanical stress?
, A. Intermediate filament
B. Microtubule
C. Actin filament
D. Septin only
Correct Answer: A. Intermediate filament
Rationale: Intermediate filaments provide tensile strength and
mechanical stability.
10. Which cytoskeletal polymer is directly involved in cell cortex
formation and many forms of cell migration?
A. Actin
B. Tubulin
C. Keratin only
D. Collagen
Correct Answer: A. Actin
Rationale: Actin filaments form the cortical cytoskeleton and participate
in protrusion, contraction, and migration.
11. What is the main function of the centrosome in animal cells?
A. Protein degradation
B. Microtubule organization
C. DNA replication
D. Lipid synthesis
Correct Answer: B. Microtubule organization
Rationale: The centrosome is a major microtubule-organizing center.
12. Which structure surrounds the nucleus?
