Question 1

Which of the following statements best describes the role of γ-tubulin in microtubule organization within animal cells?

Accepted Answer

γ-tubulin forms ring complexes that nucleate the assembly of new microtubules at the centrosome.

Question 2

A researcher treats dividing cancer cells with taxol. What is the most likely effect on microtubule dynamics and cell division?

Accepted Answer

Microtubules will become stabilized, preventing spindle disassembly and arresting cells in mitosis.

Question 3

Which cytoskeletal element is most directly responsible for resisting tensile (stretching) forces in animal cells?

Accepted Answer

Intermediate filaments

Question 4

If the concentration of free tubulin is above the critical concentration for the plus end but below that of the minus end, what will happen to microtubules in vitro?

Accepted Answer

Microtubules will treadmill, with addition at the plus end and loss at the minus end.

Question 5

Which of the following drugs would most likely inhibit the assembly of actin microfilaments by sequestering actin monomers?

Accepted Answer

Latrunculin A

Question 6

A mutation in the gene encoding the Arp2/3 complex would most directly affect which cellular process?

Accepted Answer

Formation of branched actin networks in lamellipodia

Question 7

Which protein is responsible for crosslinking actin filaments into loose networks, such as those found in the cell cortex?

Accepted Answer

Filamin

Question 8

A cell is treated with colchicine. Which process is most likely to be disrupted?

Accepted Answer

Mitotic spindle formation

Question 9

Which of the following best explains why the plus ends of actin filaments are oriented toward the tip of filopodia?

Accepted Answer

The plus end grows faster, allowing rapid extension of the protrusion.

Question 10

Which of the following statements about intermediate filaments is TRUE?

Accepted Answer

They are the most stable and least soluble cytoskeletal elements.

Question 11

Which protein is responsible for stabilizing microtubules by binding along their sides and promoting interaction with other cellular structures?

Accepted Answer

Tau (a MAP)

Question 12

A cell lacking functional Rho GTPase would most likely show defects in which structure?

Accepted Answer

Stress fibers

Question 13

Which of the following best describes the process of microtubule dynamic instability?

Accepted Answer

Microtubules alternate between phases of growth and rapid shrinkage, regulated by the presence of a GTP cap.

Question 14

Which of the following proteins severs actin filaments and caps the newly exposed plus ends, preventing further polymerization?

Accepted Answer

Gelsolin

Question 15

A patient has a genetic defect in keratin. Which tissue is most likely to be affected?

Accepted Answer

Epithelial tissue

Question 16

Which of the following best describes the role of the Arp2/3 complex in actin filament organization?

Accepted Answer

It nucleates new branches on the sides of existing filaments, creating a dendritic network.

Question 17

Which cytoskeletal element is most directly involved in the formation of the mitotic spindle?

Accepted Answer

Microtubules

Question 18

Which of the following proteins is responsible for bundling actin filaments in filopodia, keeping them tightly packed?

Accepted Answer

Fascin

Question 19

Which of the following best explains why antimitotic drugs such as vinblastine are effective in cancer treatment?

Accepted Answer

They inhibit microtubule assembly, preventing spindle formation and blocking cell division in rapidly dividing cells.

Question 20

Which of the following statements about the assembly of intermediate filaments is correct?

Accepted Answer

Intermediate filaments assemble from fibrous subunits that form coiled-coil dimers, which then assemble into tetramers and finally into filaments.

Cytoskeletal Systems: Structure, Function, and Regulation

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