Question 1

Which of the following best describes the structure of a microtubule as seen in the provided images and study materials?

Accepted Answer

A hollow tube composed of 13 protofilaments made of α/β-tubulin heterodimers

Question 2

What is the primary function of the GTP cap in microtubule dynamics?

Accepted Answer

To stabilize the plus end of the microtubule and promote further polymerization

Question 3

Which of the following drugs would you use to inhibit microtubule polymerization in a cell biology experiment?

Accepted Answer

Colchicine

Question 4

A researcher observes that microtubules in a cell are rapidly depolymerizing at 4°C. What is the most likely explanation for this observation?

Accepted Answer

Microtubule assembly is temperature-dependent and depolymerizes at low temperatures

Question 5

Which of the following best explains the phenomenon of treadmilling in microtubules?

Accepted Answer

Polymerization occurs at the plus end while depolymerization occurs at the minus end, resulting in a net movement of subunits through the microtubule

Question 6

Given the following critical concentrations: $$C_c^+ = 0.12 \ \mu M$$ and $$C_c^- = 0.60 \ \mu M$$, what will happen if the free tubulin concentration is $$0.30 \ \mu M$$?

Accepted Answer

The plus end will grow while the minus end will shrink (treadmilling)

Question 7

Which of the following statements about the polarity of microtubules is correct?

Accepted Answer

Microtubules have distinct plus and minus ends, with the plus end growing faster

Question 8

A patient is treated with Taxol for cancer. What is the mechanism of action of Taxol on microtubules?

Accepted Answer

Taxol stabilizes microtubules, preventing their depolymerization

Question 9

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

Accepted Answer

They serve as nucleation and anchoring sites for microtubules

Question 10

Which protein is responsible for forming tight bundles of microtubules in axons and is implicated in neurodegenerative diseases when misregulated?

Accepted Answer

Tau

Question 11

What is the main difference between microvilli and cilia as described in the study materials?

Accepted Answer

Microvilli are actin-based, non-motile, and mainly function in absorption, while cilia are microtubule-based, motile, and function in sweeping

Question 12

Which of the following best describes the assembly process of microtubules in vitro?

Accepted Answer

Tubulin dimers first form oligomers, then protofilaments, which associate into sheets that close to form a tube

Question 13

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

Accepted Answer

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

Question 14

A cell is treated with a drug that binds to the β-tubulin subunit and prevents GTP hydrolysis. What is the most likely effect on microtubule dynamics?

Accepted Answer

Microtubules will become overly stable and resist depolymerization

Question 15

Which of the following best explains why intermediate filaments are useful in medical diagnostics?

Accepted Answer

Their protein sequences are tissue-specific, allowing identification of cell origin in tumors

Question 16

Which of the following statements about the role of the centrosome in animal cells is correct?

Accepted Answer

It acts as the main microtubule-organizing center (MTOC) and contains a pair of centrioles

Question 17

Which of the following best describes the effect of capping proteins on actin microfilament dynamics?

Accepted Answer

They bind to filament ends and prevent further addition or loss of subunits

Question 18

Which of the following is a function shared by both microtubules and microfilaments?

Accepted Answer

Intracellular transport/trafficking

Question 19

A mutation in the Tau protein leads to its abnormal aggregation in neurons. Which disease is most closely associated with this phenomenon?

Accepted Answer

Alzheimer’s disease

The Cytoskeleton: Structure, Function, and Dynamics of Microtubules, Microfilaments, and Intermediate Filaments

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