PCB3023C Exam 4: Cell Biology 2026 FGCU
1. Which component of the cytoskeleton is responsible for forming the mitotic
spindle during cell division?
A. Microfilaments
B. Intermediate filaments
C. Septins
D. Microtubules
Answer: D
Rationale: Microtubules are the primary components of the mitotic spindle, facilitating
chromosome segregation.
2. Which of the following motor proteins typically moves toward the minus end
of a microtubule?
A. Kinesin
B. Myosin II
C. Dynein
D. Myosin V
Answer: C
Rationale: Dyneins move toward the minus end (usually the centrosome), while most
kinesins move toward the plus end.
,3. In the G-protein coupled receptor (GPCR) pathway, which molecule acts as
the second messenger after the activation of adenylyl cyclase?
A. GTP
B. IP3
C. cAMP
D. Calcium ions
Answer: C
Rationale: Adenylyl cyclase converts ATP into cyclic AMP (cAMP), which then activates
protein kinase A (PKA).
4. What is the primary role of the p53 protein in the cell cycle?
A. To trigger the start of S phase
B. To act as a transcription factor that halts the cell cycle in response to DNA damage
C. To degrade cyclins during anaphase
D. To promote phosphorylation of the Rb protein
Answer: B
Rationale: p53 is a tumor suppressor that senses DNA damage and induces cell cycle
arrest or apoptosis.
5. Which phase of the cell cycle is characterized by DNA replication?
A. G1 phase
B. M phase
C. G2 phase
D. S phase
Answer: D
Rationale: The S phase (Synthesis phase) is when the cell duplicates its genomic DNA.
, 6. The ‘dynamic instability’ of microtubules refers to their ability to:
A. Form branched networks using Arp2/3
B. Move freely within the cytoplasm
C. Bind to different types of motor proteins
D. Switch between growth and rapid shrinkage
Answer: D
Rationale: Dynamic instability involves the coexistence of growing and shrinking
microtubules in the same cytosolic region.
7. Which enzyme is responsible for the release of Cytochrome c from the
mitochondria during apoptosis?
A. Bax and Bak
B. Caspase-3
C. Bcl-2
D. Adenylyl cyclase
Answer: A
Rationale: Pro-apoptotic proteins Bax and Bak form pores in the mitochondrial outer
membrane to release Cytochrome c.
8. What occurs during the Anaphase B stage of mitosis?
A. Sister chromatids are pulled toward the poles
B. The nuclear envelope reforms
C. Spindle poles themselves move further apart
D. Chromosomes align at the metaphase plate
Answer: C
Rationale: Anaphase B involves the elongation of the spindle and the pushing apart of the
poles.
1. Which component of the cytoskeleton is responsible for forming the mitotic
spindle during cell division?
A. Microfilaments
B. Intermediate filaments
C. Septins
D. Microtubules
Answer: D
Rationale: Microtubules are the primary components of the mitotic spindle, facilitating
chromosome segregation.
2. Which of the following motor proteins typically moves toward the minus end
of a microtubule?
A. Kinesin
B. Myosin II
C. Dynein
D. Myosin V
Answer: C
Rationale: Dyneins move toward the minus end (usually the centrosome), while most
kinesins move toward the plus end.
,3. In the G-protein coupled receptor (GPCR) pathway, which molecule acts as
the second messenger after the activation of adenylyl cyclase?
A. GTP
B. IP3
C. cAMP
D. Calcium ions
Answer: C
Rationale: Adenylyl cyclase converts ATP into cyclic AMP (cAMP), which then activates
protein kinase A (PKA).
4. What is the primary role of the p53 protein in the cell cycle?
A. To trigger the start of S phase
B. To act as a transcription factor that halts the cell cycle in response to DNA damage
C. To degrade cyclins during anaphase
D. To promote phosphorylation of the Rb protein
Answer: B
Rationale: p53 is a tumor suppressor that senses DNA damage and induces cell cycle
arrest or apoptosis.
5. Which phase of the cell cycle is characterized by DNA replication?
A. G1 phase
B. M phase
C. G2 phase
D. S phase
Answer: D
Rationale: The S phase (Synthesis phase) is when the cell duplicates its genomic DNA.
, 6. The ‘dynamic instability’ of microtubules refers to their ability to:
A. Form branched networks using Arp2/3
B. Move freely within the cytoplasm
C. Bind to different types of motor proteins
D. Switch between growth and rapid shrinkage
Answer: D
Rationale: Dynamic instability involves the coexistence of growing and shrinking
microtubules in the same cytosolic region.
7. Which enzyme is responsible for the release of Cytochrome c from the
mitochondria during apoptosis?
A. Bax and Bak
B. Caspase-3
C. Bcl-2
D. Adenylyl cyclase
Answer: A
Rationale: Pro-apoptotic proteins Bax and Bak form pores in the mitochondrial outer
membrane to release Cytochrome c.
8. What occurs during the Anaphase B stage of mitosis?
A. Sister chromatids are pulled toward the poles
B. The nuclear envelope reforms
C. Spindle poles themselves move further apart
D. Chromosomes align at the metaphase plate
Answer: C
Rationale: Anaphase B involves the elongation of the spindle and the pushing apart of the
poles.
