Difficulty: Advanced / Hard / Mixed
Target Audience: College students (upper-division) and professionals
Format: One correct answer per question; conceptual, application-based, and scenario-
based items
Sources: Alberts Molecular Biology of the Cell (6th/7th ed.) test banks; Lodish Molecular
Cell Biology (9th ed.) test banks; BIO 353 / BIOL 302 advanced cell biology examination
banks; StudyX cell biology MCQ bank
Table of Contents
1. Membrane Structure and Membrane Transport (Q1–Q20)
2. Organelles, Protein Sorting, and Vesicular Traffic (Q21–Q40)
3. Cytoskeleton and Cell Motility (Q41–Q60)
4. Cell Signaling and Signal Transduction (Q61–Q80)
5. Cell Cycle Regulation and Mitosis (Q81–Q100)
6. Apoptosis and Cell Death (Q101–Q115)
7. Cancer Cell Biology (Q116–Q130)
8. Extracellular Matrix and Cell Adhesion (Q131–Q140)
9. Cellular Metabolism and Mitochondrial Function (Q141–Q150)
, 10. Answer Key with Rationales and Citations
Section 1: Membrane Structure and Membrane Transport
🟢 Q1. A newly discovered extremophile possesses membrane lipids with ether linkages
and branched hydrocarbon chains. Compared with standard eukaryotic phospholipids,
which property of this membrane would be most directly enhanced?
A. Lateral diffusion rate of integral proteins
B. Resistance to thermal denaturation and chemical hydrolysis
C. Permeability to small nonpolar solutes
D. Susceptibility to phospholipase A₂ cleavage
E. Fluidity at low temperatures
🔴🔴 B. Resistance to thermal denaturation and chemical hydrolysis
Rationale: Ether linkages are far more resistant to hydrolysis than ester bonds, and
branched chains pack more stably at high temperatures. This is a classic archaeal
membrane adaptation. Lateral diffusion, permeability, and phospholipase susceptibility
are not the primary consequences of ether branching.
🟢 Q2. In a FRAP (fluorescence recovery after photobleaching) experiment, a GFP-tagged
plasma membrane protein shows rapid lateral recovery after bleaching. Which
cytoskeletal element, if disrupted, would most likely reduce this mobility?
A. Actin microfilaments
B. Microtubules
C. Intermediate filaments
,D. Septin rings
E. Spectrin meshwork
🔴🔴 A. Actin microfilaments
Rationale: The actin-based membrane skeleton (cortical actin) creates diffusion barriers
and corrals. Disrupting actin increases—rather than reduces—mobility of many
membrane proteins. Microtubules and intermediate filaments do not primarily restrict
lateral diffusion of plasma membrane proteins in this context.
🟢 Q3. The selectivity filter of a K⁺ channel achieves >10,000-fold selectivity for K⁺ over
Na⁺. Which statement best explains this?
A. K⁺ is smaller than Na⁺ and therefore enters the pore more easily.
B. The filter provides precisely spaced carbonyl oxygens that mimic the hydration shell
of K⁺ but not Na⁺.
C. Na⁺ is actively pumped out of the pore by an adjacent ATPase.
D. The pore is lined with negatively charged residues that repel Na⁺.
E. K⁺ channels are open only when the membrane is depolarized.
🔴🔴 B. The filter provides precisely spaced carbonyl oxygens that mimic the hydration
shell of K⁺ but not Na⁺.
Rationale: The K⁺ channel selectivity filter dehydrates K⁺ and coordinates it with
backbone carbonyls at an ideal distance. Na⁺, being smaller, cannot be coordinated with
the same geometry and remains preferentially hydrated.
🟢 Q4. A patient carries a mutation that eliminates the Na⁺/K⁺-ATPase pump in neurons.
Which immediate consequence is most likely?
, A. Increased resting membrane potential magnitude (hyperpolarization)
B. Gradual loss of the resting membrane potential and cell swelling
C. Enhanced action potential amplitude
D. Increased intracellular K⁺ and decreased intracellular Na⁺
E. Complete block of neurotransmitter release
🔴🔴 B. Gradual loss of the resting membrane potential and cell swelling
Rationale: The Na⁺/K⁺ pump maintains the ionic gradients that underlie the resting
potential and controls cell volume. Without it, Na⁺ accumulates intracellularly, K⁺ leaks
out, and osmotic swelling occurs.
🟢 Q5. A v-type H⁺-ATPase acidifies the lysosomal lumen. This transport process is best
classified as:
A. Primary active transport
B. Secondary active transport
C. Facilitated diffusion
D. Simple diffusion
E. Group translocation
🔴🔴 A. Primary active transport
Rationale: The v-type H⁺-ATPase directly hydrolyzes ATP to pump protons against their
gradient. This is the definition of primary active transport. Secondary active transport
would couple proton movement to another solute's gradient.
🟢 Q6. In an experiment, a cell is placed in a hypotonic solution and swells but does not
lyse immediately. Which membrane feature most likely prevents rupture?
Target Audience: College students (upper-division) and professionals
Format: One correct answer per question; conceptual, application-based, and scenario-
based items
Sources: Alberts Molecular Biology of the Cell (6th/7th ed.) test banks; Lodish Molecular
Cell Biology (9th ed.) test banks; BIO 353 / BIOL 302 advanced cell biology examination
banks; StudyX cell biology MCQ bank
Table of Contents
1. Membrane Structure and Membrane Transport (Q1–Q20)
2. Organelles, Protein Sorting, and Vesicular Traffic (Q21–Q40)
3. Cytoskeleton and Cell Motility (Q41–Q60)
4. Cell Signaling and Signal Transduction (Q61–Q80)
5. Cell Cycle Regulation and Mitosis (Q81–Q100)
6. Apoptosis and Cell Death (Q101–Q115)
7. Cancer Cell Biology (Q116–Q130)
8. Extracellular Matrix and Cell Adhesion (Q131–Q140)
9. Cellular Metabolism and Mitochondrial Function (Q141–Q150)
, 10. Answer Key with Rationales and Citations
Section 1: Membrane Structure and Membrane Transport
🟢 Q1. A newly discovered extremophile possesses membrane lipids with ether linkages
and branched hydrocarbon chains. Compared with standard eukaryotic phospholipids,
which property of this membrane would be most directly enhanced?
A. Lateral diffusion rate of integral proteins
B. Resistance to thermal denaturation and chemical hydrolysis
C. Permeability to small nonpolar solutes
D. Susceptibility to phospholipase A₂ cleavage
E. Fluidity at low temperatures
🔴🔴 B. Resistance to thermal denaturation and chemical hydrolysis
Rationale: Ether linkages are far more resistant to hydrolysis than ester bonds, and
branched chains pack more stably at high temperatures. This is a classic archaeal
membrane adaptation. Lateral diffusion, permeability, and phospholipase susceptibility
are not the primary consequences of ether branching.
🟢 Q2. In a FRAP (fluorescence recovery after photobleaching) experiment, a GFP-tagged
plasma membrane protein shows rapid lateral recovery after bleaching. Which
cytoskeletal element, if disrupted, would most likely reduce this mobility?
A. Actin microfilaments
B. Microtubules
C. Intermediate filaments
,D. Septin rings
E. Spectrin meshwork
🔴🔴 A. Actin microfilaments
Rationale: The actin-based membrane skeleton (cortical actin) creates diffusion barriers
and corrals. Disrupting actin increases—rather than reduces—mobility of many
membrane proteins. Microtubules and intermediate filaments do not primarily restrict
lateral diffusion of plasma membrane proteins in this context.
🟢 Q3. The selectivity filter of a K⁺ channel achieves >10,000-fold selectivity for K⁺ over
Na⁺. Which statement best explains this?
A. K⁺ is smaller than Na⁺ and therefore enters the pore more easily.
B. The filter provides precisely spaced carbonyl oxygens that mimic the hydration shell
of K⁺ but not Na⁺.
C. Na⁺ is actively pumped out of the pore by an adjacent ATPase.
D. The pore is lined with negatively charged residues that repel Na⁺.
E. K⁺ channels are open only when the membrane is depolarized.
🔴🔴 B. The filter provides precisely spaced carbonyl oxygens that mimic the hydration
shell of K⁺ but not Na⁺.
Rationale: The K⁺ channel selectivity filter dehydrates K⁺ and coordinates it with
backbone carbonyls at an ideal distance. Na⁺, being smaller, cannot be coordinated with
the same geometry and remains preferentially hydrated.
🟢 Q4. A patient carries a mutation that eliminates the Na⁺/K⁺-ATPase pump in neurons.
Which immediate consequence is most likely?
, A. Increased resting membrane potential magnitude (hyperpolarization)
B. Gradual loss of the resting membrane potential and cell swelling
C. Enhanced action potential amplitude
D. Increased intracellular K⁺ and decreased intracellular Na⁺
E. Complete block of neurotransmitter release
🔴🔴 B. Gradual loss of the resting membrane potential and cell swelling
Rationale: The Na⁺/K⁺ pump maintains the ionic gradients that underlie the resting
potential and controls cell volume. Without it, Na⁺ accumulates intracellularly, K⁺ leaks
out, and osmotic swelling occurs.
🟢 Q5. A v-type H⁺-ATPase acidifies the lysosomal lumen. This transport process is best
classified as:
A. Primary active transport
B. Secondary active transport
C. Facilitated diffusion
D. Simple diffusion
E. Group translocation
🔴🔴 A. Primary active transport
Rationale: The v-type H⁺-ATPase directly hydrolyzes ATP to pump protons against their
gradient. This is the definition of primary active transport. Secondary active transport
would couple proton movement to another solute's gradient.
🟢 Q6. In an experiment, a cell is placed in a hypotonic solution and swells but does not
lyse immediately. Which membrane feature most likely prevents rupture?
