Q: Which equation best represents the relationship between the rate of actin filament assembly ($$R_{assembly}) $$and the concentration of actin monomers ($$[A]$$), assuming assembly is directly proportional to monomer concentration?

$$R_{assembly} = k \times [A]$$

Question 1

Which of the following statements best describes the primary function of intermediate filaments in animal cells?

Accepted Answer

They provide tensile strength and mechanical stability to cells.

Question 2

A scientist treats fibroblast cells with phalloidin, a toxin that binds and stabilizes actin filaments. What is the most likely effect on actin dynamics in these cells?

Accepted Answer

Actin filament turnover will decrease, leading to stabilized filaments.

Question 3

Microtubules exhibit dynamic instability, which is crucial for their cellular functions. Which molecular event triggers 'catastrophe' in microtubules?

Accepted Answer

Hydrolysis of GTP to GDP on beta-tubulin near the plus end.

Question 4

Which cytoskeletal element is most directly responsible for the movement of cilia and flagella?

Accepted Answer

Microtubules

Question 5

A nerve cell must transport vesicles from the cell body to the axon terminal. Which cytoskeletal structure and associated proteins are primarily involved in this process?

Accepted Answer

Microtubules and kinesin

Question 6

Which of the following best explains why microtubules are considered 'polarized' structures?

Accepted Answer

They have distinct plus and minus ends, with assembly occurring preferentially at the plus end.

Question 7

Which cytoskeletal component is most likely to be tissue-specific and provide structural support at cell-cell junctions?

Accepted Answer

Intermediate filaments

Question 8

During cell migration, which actin-based structure forms at the leading edge of a moving cell and is responsible for pushing the plasma membrane forward?

Accepted Answer

Lamellipodium

Question 9

Which of the following best describes the role of microtubule-organizing centers (MTOCs) in animal cells?

Accepted Answer

They nucleate and organize the growth of microtubules, with minus ends anchored to the centrosome.

Question 10

A mutation in the gene encoding beta-tubulin affects its ability to bind GTP. What is the most likely consequence for microtubule dynamics in the cell?

Accepted Answer

Microtubule assembly will be impaired, leading to reduced dynamic instability.

Question 11

Which equation best represents the relationship between the rate of actin filament assembly ($$R_{assembly}) $$and the concentration of actin monomers ($$[A]$$), assuming assembly is directly proportional to monomer concentration?

Accepted Answer

$$R_{assembly} = k 	imes [A]$$

Question 12

Which cytoskeletal structure is most likely to be disrupted in a patient with a genetic disorder affecting keratin proteins, leading to fragile skin and blistering?

Accepted Answer

Intermediate filaments

Question 13

Which of the following statements about actin filaments is TRUE?

Accepted Answer

Actin filaments are double-stranded polymers that bind ATP.

Question 14

A cell is observed to have defective vesicle transport along its axon. Which cytoskeletal element and associated protein are most likely malfunctioning?

Accepted Answer

Microtubules and kinesin

Question 15

Which of the following best explains why intermediate filaments are more stable than microtubules or microfilaments?

Accepted Answer

They are made of fibrous dimers that assemble into rope-like structures.

Question 16

Which cytoskeletal element is most important for the formation of microvilli on the surface of intestinal epithelial cells?

Accepted Answer

Microfilaments (actin filaments)

Question 17

During mitosis, which cytoskeletal structure forms the spindle apparatus responsible for chromosome alignment and separation?

Accepted Answer

Microtubules

Question 18

Which of the following proteins is most likely to stimulate actin polymerization at the leading edge of a migrating cell?

Accepted Answer

Formin

Question 19

A cell is exposed to a drug that sequesters actin monomers. What is the most likely effect on the cell's cytoskeleton?

Accepted Answer

Actin filament assembly will decrease.

Question 20

Which of the following best describes the structural organization of a microtubule?

Accepted Answer

A hollow tube composed of protofilaments made from alpha and beta tubulin heterodimers.

The Cytoskeleton: Structure and Function in Eukaryotic Cells

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