Question 1

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

Accepted Answer

They provide tensile strength to cells, helping them withstand mechanical stress.

Question 2

A scientist treats fibroblast cells with a drug that sequesters actin monomers, preventing their polymerization. What is the most likely effect on the cell?

Accepted Answer

The cell will lose its ability to form lamellipodia and filopodia, impairing cell movement.

Question 3

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

Accepted Answer

Microtubules

Question 4

Microtubules exhibit 'dynamic instability.' Which molecular event is primarily responsible for the transition from growth to rapid shrinkage (catastrophe) in microtubules?

Accepted Answer

Hydrolysis of GTP to GDP on the beta-tubulin subunit at the plus end

Question 5

A mutation in a gene encoding a microtubule-associated protein (MAP) that stabilizes microtubules would most likely result in which cellular phenotype?

Accepted Answer

Increased frequency of microtubule catastrophes and reduced cell polarity

Question 6

Which of the following statements about actin filaments (microfilaments) is correct?

Accepted Answer

They are double-stranded polymers of actin that bind ATP and are polarized.

Question 7

During axonal transport in nerve cells, which cytoskeletal structure serves as the primary track for vesicle movement?

Accepted Answer

Microtubules

Question 8

A patient has a genetic disorder affecting the protein keratin. Which tissue is most likely to be affected and why?

Accepted Answer

Epithelial tissue, because keratin is a type of intermediate filament providing mechanical strength.

Question 9

Which of the following best explains why microtubules grow and shrink more rapidly at their plus ends than at their minus ends?

Accepted Answer

The plus end is less stably anchored and has a higher rate of tubulin addition and loss.

Question 10

Which of the following is a key difference between microtubules and intermediate filaments?

Accepted Answer

Microtubules are dynamic and polarized, while intermediate filaments are more stable and non-polar.

Question 11

A researcher observes that after treating cells with phalloidin, actin filaments become stabilized and do not depolymerize. What conclusion can be drawn from this experiment?

Accepted Answer

Phalloidin binds to actin filaments and prevents their depolymerization, stabilizing the cytoskeleton.

Question 12

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

Accepted Answer

It nucleates and anchors the minus ends of microtubules, organizing their growth and polarity.

Question 13

Which of the following scenarios would most likely result in the greatest dynamic instability of microtubules?

Accepted Answer

During mitosis, when rapid assembly and disassembly are required for spindle formation.

Question 14

Which of the following best explains why actin filaments are important for the formation of microvilli in intestinal epithelial cells?

Accepted Answer

Actin filaments form the core structure of microvilli, providing support and shape.

Question 15

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

Accepted Answer

They are composed of fibrous dimers that assemble into rope-like polymers, providing mechanical strength.

Question 16

A cell is observed to have defective vesicle transport along its axon. Which cytoskeletal component and associated process is most likely impaired?

Accepted Answer

Microtubules and their polarity-dependent motor protein transport

Question 17

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

Accepted Answer

They have a plus end where monomers add more rapidly and a minus end where disassembly is favored.

Question 18

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

Accepted Answer

Intermediate filaments

Question 19

A cell is exposed to a toxin that prevents the hydrolysis of GTP on beta-tubulin. What is the most likely effect on microtubule dynamics?

Accepted Answer

Microtubules will become excessively stable and fail to undergo normal dynamic instability.

The Cytoskeleton: Structure and Function in Eukaryotic Cells

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