Question 1

Which of the following statements best describes the role of cytoskeletal proteins in eukaryotic cells?

Accepted Answer

They are involved in supporting cell structure, moving materials within the cell, and enabling cell movement.

Question 2

A scientist treats fibroblasts with phalloidin, a toxin that binds and stabilizes actin filaments. What is the most likely effect on the cell?

Accepted Answer

Actin filaments will become stabilized, preventing their normal dynamic rearrangement.

Question 3

Which cytoskeletal element is primarily responsible for the movement of vesicles along axons in nerve cells?

Accepted Answer

Microtubules

Question 4

Microtubules are composed of which type of protein subunits?

Accepted Answer

Alpha and beta tubulin heterodimers

Question 5

Which of the following best explains the concept of 'dynamic instability' in microtubules?

Accepted Answer

Microtubules alternate between rapid growth and shrinkage due to GTP hydrolysis.

Question 6

Given the following diameters, which cytoskeletal element is the thickest?

Accepted Answer

Microtubules ($$25\ \mathrm{nm})$$

Question 7

Which cytoskeletal structure is most directly involved in the formation of the contractile ring during cytokinesis?

Accepted Answer

Microfilaments (actin filaments)

Question 8

A mutation disrupts the function of $$eta-$$tubulin in a cell. Which process would be most directly affected?

Accepted Answer

Assembly and function of microtubules

Question 9

Which of the following proteins is most likely to regulate the polymerization of actin filaments by sequestering actin monomers?

Accepted Answer

Thymosin $$\$$beta_4$$

Question 10

Intermediate filaments are best characterized by which property?

Accepted Answer

They provide tensile strength and are more stable than microtubules or microfilaments.

Question 11

Which cytoskeletal element is most likely to be tissue-specific in its protein composition?

Accepted Answer

Intermediate filaments

Question 12

During cell migration, which actin-based structure is responsible for sensing the environment and directing movement?

Accepted Answer

Filopodium

Question 13

Which of the following best describes the polarity of actin filaments?

Accepted Answer

They have a plus end where monomers add preferentially and a minus end where disassembly occurs.

Question 14

A cell is observed to have defective vesicle transport. Which cytoskeletal structure and associated proteins are most likely involved?

Accepted Answer

Microtubules and motor proteins such as kinesin and dynein

Question 15

Which of the following is a major microtubule-organizing center (MTOC) in animal cells?

Accepted Answer

Centrosome

Question 16

What is the primary function of intermediate filaments at cell-cell junctions?

Accepted Answer

Provide mechanical strength and stability to tissues

Question 17

Which cytoskeletal element is most directly involved in the movement of cilia and flagella?

Accepted Answer

Microtubules

Question 18

If a cell's microtubules are destabilized by loss of the GTP cap, what is the most likely outcome?

Accepted Answer

Microtubules will undergo catastrophic shortening.

Question 19

Which cytoskeletal element is most abundant in the cell cortex and is essential for maintaining cell shape and enabling cell movement?

Accepted Answer

Microfilaments (actin filaments)

Question 20

A patient has a genetic disorder affecting keratin proteins. Which cellular structure is most likely compromised?

Accepted Answer

Intermediate filaments

The Cytoskeleton: Structure and Function in Eukaryotic Cells

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