Page 1 of 205
San Francisco State University – BIO 240 Exam
3 Actual– Full 100-Question Study Guide
Comprehensive Questions with Answers and
Explanations| PDF
Question 1
Which of the following cytoskeletal components is primarily
responsible for resisting tension (pulling forces) in a cell?
A) Microtubules
B) Intermediate filaments
C) Microfilaments (Actin filaments)
D) Septins
Correct Answer: B
Rationale: Intermediate filaments (e.g., keratins, lamins) are
rope-like structures that provide mechanical strength and resist
tension. They are the most stable and least dynamic of the
,Page 2 of 205
cytoskeletal elements. Microfilaments resist tension but also
participate in contraction; microtubules resist compression.
Intermediate filaments are specifically specialized for tension
resistance and anchoring organelles.
Question 2
A researcher treats cells with a drug that depolymerizes all
microtubules. Which cellular process will be most immediately
disrupted?
A) Muscle contraction
B) Cell crawling via lamellipodia
C) Chromosome separation during mitosis
D) Maintenance of cell shape by the cortex
Correct Answer: C
Rationale: Microtubules form the mitotic spindle, which is
essential for separating chromosomes during anaphase.
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Depolymerizing them prevents spindle formation and arrests cells
in mitosis. Muscle contraction relies on actin/myosin, cell crawling
on actin dynamics, and the cell cortex on actin. Thus, chromosome
separation is the most immediately affected process.
Question 3
[SCENARIO] A patient is diagnosed with a mutation in the gene
encoding dynein. Which of the following clinical findings would
you most expect?
A) Inability to form lamellipodia during wound healing
B) Primary ciliary dyskinesia (chronic respiratory infections and
infertility)
C) Muscular dystrophy
D) Defective cytokinesis
Correct Answer: B
, Page 4 of 205
Rationale: Dynein is the motor protein responsible for the
movement of cilia and flagella. Mutations in dynein cause
primary ciliary dyskinesia (Kartagener syndrome), characterized
by immotile cilia, leading to chronic respiratory infections, situs
inversus, and male infertility. Lamellipodia involve actin; muscular
dystrophy involves dystrophin; cytokinesis involves the contractile
ring (actin/myosin).
Question 4
Which motor protein moves toward the minus-end of a
microtubule?
A) Kinesin-1
B) Myosin V
C) Dynein
D) Kinesin-13
Correct Answer: C
San Francisco State University – BIO 240 Exam
3 Actual– Full 100-Question Study Guide
Comprehensive Questions with Answers and
Explanations| PDF
Question 1
Which of the following cytoskeletal components is primarily
responsible for resisting tension (pulling forces) in a cell?
A) Microtubules
B) Intermediate filaments
C) Microfilaments (Actin filaments)
D) Septins
Correct Answer: B
Rationale: Intermediate filaments (e.g., keratins, lamins) are
rope-like structures that provide mechanical strength and resist
tension. They are the most stable and least dynamic of the
,Page 2 of 205
cytoskeletal elements. Microfilaments resist tension but also
participate in contraction; microtubules resist compression.
Intermediate filaments are specifically specialized for tension
resistance and anchoring organelles.
Question 2
A researcher treats cells with a drug that depolymerizes all
microtubules. Which cellular process will be most immediately
disrupted?
A) Muscle contraction
B) Cell crawling via lamellipodia
C) Chromosome separation during mitosis
D) Maintenance of cell shape by the cortex
Correct Answer: C
Rationale: Microtubules form the mitotic spindle, which is
essential for separating chromosomes during anaphase.
,Page 3 of 205
Depolymerizing them prevents spindle formation and arrests cells
in mitosis. Muscle contraction relies on actin/myosin, cell crawling
on actin dynamics, and the cell cortex on actin. Thus, chromosome
separation is the most immediately affected process.
Question 3
[SCENARIO] A patient is diagnosed with a mutation in the gene
encoding dynein. Which of the following clinical findings would
you most expect?
A) Inability to form lamellipodia during wound healing
B) Primary ciliary dyskinesia (chronic respiratory infections and
infertility)
C) Muscular dystrophy
D) Defective cytokinesis
Correct Answer: B
, Page 4 of 205
Rationale: Dynein is the motor protein responsible for the
movement of cilia and flagella. Mutations in dynein cause
primary ciliary dyskinesia (Kartagener syndrome), characterized
by immotile cilia, leading to chronic respiratory infections, situs
inversus, and male infertility. Lamellipodia involve actin; muscular
dystrophy involves dystrophin; cytokinesis involves the contractile
ring (actin/myosin).
Question 4
Which motor protein moves toward the minus-end of a
microtubule?
A) Kinesin-1
B) Myosin V
C) Dynein
D) Kinesin-13
Correct Answer: C
