PCB3023C Exam 4: Cell Biology Comprehensive Quiz 2026 |FGCU
1. In G-protein coupled receptor signaling, what is the immediate effect of
ligand binding to the receptor?
A. Phosphorylation of the G-protein alpha subunit
B. Conformational change that allows the receptor to act as a GEF
C. Direct activation of Adenylate Cyclase
D. Degradation of the G-protein beta-gamma complex
Answer: B
Rationale: Ligand binding induces a conformational change in the GPCR, allowing it to act
as a Guanine nucleotide Exchange Factor (GEF) for the G-protein.
2. Which molecule acts as a second messenger by opening calcium channels on
the endoplasmic reticulum?
A. cAMP
B. Diacylglycerol (DAG)
C. cGMP
D. Inositol 1,4,5-trisphosphate (IP3)
Answer: D
Rationale: IP3 is produced by the cleavage of PIP2 and binds to receptors on the ER to
release calcium into the cytosol.
,3. Which motor protein is primarily responsible for retrograde transport
(toward the minus end) along microtubules?
A. Kinesin
B. Dynein
C. Myosin II
D. Myosin V
Answer: B
Rationale: Dyneins move toward the minus ends of microtubules (retrograde), while most
kinesins move toward the plus ends (anterograde).
4. What is the primary role of the Cyclin-Dependent Kinase (CDK) inhibitor p21?
A. Stopping the cell cycle in response to DNA damage
B. Promoting the degradation of Cyclin D
C. Activating the Anaphase Promoting Complex
D. Phosphorylating the Rb protein
Answer: A
Rationale: p21 is a CKI induced by p53 in response to DNA damage; it binds to and inhibits
G1/S-CDK and S-CDK complexes.
5. Which of the following occurs during the ‘Anaphase B’ phase of mitosis?
A. Shortening of the kinetochore microtubules
B. Alignment of chromosomes at the metaphase plate
C. Re-formation of the nuclear envelope
D. Sliding of interpolar microtubules to push poles apart
Answer: D
Rationale: Anaphase B involves the spindle poles moving further apart driven by
interpolar microtubule elongation and motor proteins.
, 6. What triggers the activation of the Intrinsic Pathway of apoptosis?
A. Binding of Fas ligand to a death receptor
B. Activation of Caspase-8 by DISC
C. Release of Cytochrome c from the mitochondria
D. Inhibition of BAX and BAK proteins
Answer: C
Rationale: The intrinsic pathway is characterized by mitochondrial outer membrane
permeabilization and the release of Cytochrome c into the cytosol.
7. Which protein complex is responsible for attaching the spindle microtubules
to the centromere of a chromosome?
A. Cohesin
B. Kinetochore
C. Condensin
D. Separase
Answer: B
Rationale: The kinetochore is a large protein complex assembled on the centromeric DNA
that captures spindle microtubules.
8. Taxol is a chemotherapy drug that kills cancer cells by:
A. Preventing microtubule polymerization
B. Inhibiting actin filament formation
C. Stabilizing microtubules and preventing depolymerization
D. Breaking down the nuclear lamina
Answer: C
Rationale: Taxol binds to and stabilizes microtubules, preventing the dynamic instability
required for mitosis, thus arresting cells in M phase.
1. In G-protein coupled receptor signaling, what is the immediate effect of
ligand binding to the receptor?
A. Phosphorylation of the G-protein alpha subunit
B. Conformational change that allows the receptor to act as a GEF
C. Direct activation of Adenylate Cyclase
D. Degradation of the G-protein beta-gamma complex
Answer: B
Rationale: Ligand binding induces a conformational change in the GPCR, allowing it to act
as a Guanine nucleotide Exchange Factor (GEF) for the G-protein.
2. Which molecule acts as a second messenger by opening calcium channels on
the endoplasmic reticulum?
A. cAMP
B. Diacylglycerol (DAG)
C. cGMP
D. Inositol 1,4,5-trisphosphate (IP3)
Answer: D
Rationale: IP3 is produced by the cleavage of PIP2 and binds to receptors on the ER to
release calcium into the cytosol.
,3. Which motor protein is primarily responsible for retrograde transport
(toward the minus end) along microtubules?
A. Kinesin
B. Dynein
C. Myosin II
D. Myosin V
Answer: B
Rationale: Dyneins move toward the minus ends of microtubules (retrograde), while most
kinesins move toward the plus ends (anterograde).
4. What is the primary role of the Cyclin-Dependent Kinase (CDK) inhibitor p21?
A. Stopping the cell cycle in response to DNA damage
B. Promoting the degradation of Cyclin D
C. Activating the Anaphase Promoting Complex
D. Phosphorylating the Rb protein
Answer: A
Rationale: p21 is a CKI induced by p53 in response to DNA damage; it binds to and inhibits
G1/S-CDK and S-CDK complexes.
5. Which of the following occurs during the ‘Anaphase B’ phase of mitosis?
A. Shortening of the kinetochore microtubules
B. Alignment of chromosomes at the metaphase plate
C. Re-formation of the nuclear envelope
D. Sliding of interpolar microtubules to push poles apart
Answer: D
Rationale: Anaphase B involves the spindle poles moving further apart driven by
interpolar microtubule elongation and motor proteins.
, 6. What triggers the activation of the Intrinsic Pathway of apoptosis?
A. Binding of Fas ligand to a death receptor
B. Activation of Caspase-8 by DISC
C. Release of Cytochrome c from the mitochondria
D. Inhibition of BAX and BAK proteins
Answer: C
Rationale: The intrinsic pathway is characterized by mitochondrial outer membrane
permeabilization and the release of Cytochrome c into the cytosol.
7. Which protein complex is responsible for attaching the spindle microtubules
to the centromere of a chromosome?
A. Cohesin
B. Kinetochore
C. Condensin
D. Separase
Answer: B
Rationale: The kinetochore is a large protein complex assembled on the centromeric DNA
that captures spindle microtubules.
8. Taxol is a chemotherapy drug that kills cancer cells by:
A. Preventing microtubule polymerization
B. Inhibiting actin filament formation
C. Stabilizing microtubules and preventing depolymerization
D. Breaking down the nuclear lamina
Answer: C
Rationale: Taxol binds to and stabilizes microtubules, preventing the dynamic instability
required for mitosis, thus arresting cells in M phase.
