Question 1

Which of the following best describes the primary structure of microfilaments in eukaryotic cells?

Accepted Answer

Microfilaments are composed of actin monomers polymerized into a double helical filament.

Question 2

Which motor protein is directly associated with microfilaments and is responsible for generating force during muscle contraction?

Accepted Answer

Myosin

Question 3

In epithelial cells, actin assembly forms which of the following structures that is crucial for maintaining cell shape and polarity?

Accepted Answer

Microvilli

Question 4

Which factor is primarily responsible for promoting actin branching during cytoskeletal remodeling?

Accepted Answer

Arp2/3 complex

Question 5

WASP (Wiskott-Aldrich Syndrome Protein) is essential for normal actin polymerization. Loss of function mutations in WASP result in Wiskott-Aldrich Syndrome because:

Accepted Answer

WASP activates the Arp2/3 complex, and its loss impairs immune cell migration and phagocytosis.

Question 6

During Listeria infection, the bacterium hijacks the host cell's actin cytoskeleton to move within and between cells. Which process is most directly involved in this movement?

Accepted Answer

Actin polymerization at the bacterial surface forms a comet tail propelling Listeria.

Question 7

Which of the following best describes the role of the Rho family of GTPases in actin-associated processes?

Accepted Answer

They regulate actin cytoskeleton dynamics by controlling polymerization, branching, and contraction.

Question 8

Cell migration involves several steps. Which sequence correctly represents the order of events during cell crawling?

Accepted Answer

Protrusion, adhesion, contraction, retraction

Question 9

Which protein is primarily responsible for forming the protrusive structures (lamellipodia) at the leading edge of migrating cells?

Accepted Answer

Arp2/3 complex

Question 10

Cell migration must be tightly controlled. Which of the following is a real-world consequence of dysregulated cell migration?

Accepted Answer

Uncontrolled cell migration can lead to cancer metastasis.

Question 11

Which equation best represents the rate of actin polymerization, considering the concentration of actin monomers ($$[A]) $$and the rate constant ($$k$$)?

Accepted Answer

$$	ext{Rate} = k \cdot [A]$$

Question 12

A mutation in the gene encoding WASP results in defective immune cell migration. Which cellular process is most likely impaired?

Accepted Answer

Formation of actin-rich protrusions required for chemotaxis.

Question 13

Which of the following factors can influence the directionality of cell migration in a wound healing scenario?

Accepted Answer

Gradient of chemotactic signals such as growth factors.

Question 14

In mesenchymal cells, actin assembly forms stress fibers. What is the primary function of these structures?

Accepted Answer

Generate contractile force for cell movement and shape changes.

Question 15

Which signaling pathway is most directly involved in regulating actin polymerization during cell migration?

Accepted Answer

Rho GTPase pathway

Question 16

A researcher observes that Listeria is unable to move within host cells after treatment with an Arp2/3 inhibitor. What is the most likely explanation?

Accepted Answer

Actin branching is inhibited, preventing formation of the comet tail.

Question 17

Which of the following best explains why actin polymerization must be regulated during cell migration?

Accepted Answer

Unregulated polymerization can lead to loss of cell polarity and uncontrolled movement.

Question 18

During cell crawling, which protein is most directly involved in the contraction phase that pulls the cell body forward?

Accepted Answer

Myosin II

Question 19

Which of the following scenarios best illustrates the importance of controlled cell migration in development?

Accepted Answer

Neural crest cells migrate to form diverse tissues during embryogenesis.

Question 20

A patient with Wiskott-Aldrich Syndrome is found to have defective actin branching. Which cellular function is most likely compromised?

Accepted Answer

Phagocytosis by immune cells

Cell Biology Study Guide: Cytoskeleton, Actin, and Cell Migration

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