Question 1

Which cytoskeletal element is primarily responsible for resisting compression forces within the cell, and what is its main structural protein?

Accepted Answer

Microtubules; tubulin

Question 2

A patient is treated with colchicine, a drug that binds tubulin monomers. What is the most likely cellular effect?

Accepted Answer

Inhibition of microtubule assembly

Question 3

Which protein is responsible for forming tight bundles of microtubules in axons, and how does it achieve this?

Accepted Answer

Tau; by binding to the microtubule wall and extending an arm to control spacing

Question 4

Which drug would you use to stabilize microfilaments and prevent their depolymerization?

Accepted Answer

Phalloidin

Question 5

During mitosis, the mesh organelle stabilizes kinetochore fibers. Which protein is a key component of the mesh, and what is its role?

Accepted Answer

Clathrin; bridges adjacent microtubules by binding TACC3 complexes

Question 6

What is the effect of a high concentration of GTP-tubulin subunits on microtubule dynamics?

Accepted Answer

Promotes microtubule growth by maintaining the GTP cap

Question 7

Which protein acts as a +–TIP and stabilizes the growing plus end of microtubules?

Accepted Answer

CLIP-170

Question 8

A mutation in the nuclear lamins (Class V intermediate filaments) would most likely affect which cellular process?

Accepted Answer

Disassembly and reassembly of the nuclear envelope during mitosis

Question 9

Which actin-binding protein is responsible for severing actin filaments, and what is the consequence of its activity?

Accepted Answer

Gelsolin; increases the number of filament ends for rapid depolymerization

Question 10

Which cytoskeletal element is NOT polarized and is the most stable and least soluble?

Accepted Answer

Intermediate filaments

Question 11

A cell treated with nocodazole will experience which effect on its microtubules?

Accepted Answer

Inhibition of β-tubulin polymerization

Question 12

Which class of intermediate filament proteins is found in connective tissue and muscle cells?

Accepted Answer

Class III

Question 13

Which equation best describes the rate of microtubule polymerization when GTP-tubulin concentration is high?

Accepted Answer

$$r = k_{on} [Tubulin-GTP] - k_{off}$$

Question 14

Which drug would most likely disrupt cell migration by preventing actin polymerization?

Accepted Answer

Cytochalasin D

Question 15

Which protein complex is recruited to microtubules by TACC3 and is regulated by Aurora-A kinase phosphorylation?

Accepted Answer

ch-TOG

Question 16

Which cytoskeletal element forms the structural core of microvilli?

Accepted Answer

Microfilaments

Question 17

Which linker protein connects intermediate filaments, microfilaments, and microtubules, integrating the cytoskeleton?

Accepted Answer

Plectin

Question 18

Which scenario best illustrates the concept of 'dynamic instability' in microtubules?

Accepted Answer

Microtubules grow and shrink rapidly due to GTP cap loss and gain

Question 19

Which protein prevents the polymerization of tubulin by binding to tubulin heterodimers?

Accepted Answer

Stathmin/Op18

Question 20

Which cytoskeletal element is most likely to confer mechanical strength and elasticity to tissues?

Accepted Answer

Intermediate filaments

Cytoskeletal Systems: Structure, Regulation, and Function

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