Question 1

Which cytoskeletal element is primarily responsible for maintaining cell shape and polarity in animal cells?

Accepted Answer

Microtubules

Question 2

A drug binds to tubulin monomers and inhibits their assembly. Which cellular process would be most directly affected?

Accepted Answer

Chromosome movement during mitosis

Question 3

Microtubule assembly is polar. Which end of the microtubule typically grows faster?

Accepted Answer

Plus end

Question 4

During microtubule treadmilling, what happens to tubulin subunits at the plus and minus ends?

Accepted Answer

Subunits are added at the plus end and lost at the minus end

Question 5

Which equation best describes the kinetics of microtubule assembly during the elongation phase?

Accepted Answer

$$\Delta [MT] = k_{on}[Tubulin] - k_{off}[MT]$$

Question 6

Which cytoskeletal element is most abundant in the cell cortex and is involved in cell crawling?

Accepted Answer

Actin filaments (microfilaments)

Question 7

A patient is treated with Taxol, a drug that stabilizes microtubules. What is the most likely effect on cell division?

Accepted Answer

Mitotic spindle cannot disassemble, blocking cell division

Question 8

Which structure is composed of actin filaments crosslinked by bundling proteins and is found in intestinal microvilli?

Accepted Answer

Parallel bundle

Question 9

Listeria monocytogenes uses actin filaments to invade cells. Which process does this mimic in normal cell biology?

Accepted Answer

Cell locomotion via actin polymerization

Question 10

Which class of intermediate filaments forms a nuclear scaffold to give shape to the nucleus?

Accepted Answer

Lamin proteins (Class V)

Question 11

Which property distinguishes intermediate filaments from microtubules and microfilaments?

Accepted Answer

High mechanical strength and lack of polarity

Question 12

Which actin-binding protein is responsible for severing actin filaments?

Accepted Answer

Gelsolin

Question 13

A cell treated with cytochalasin D would most likely show which effect?

Accepted Answer

Inhibition of actin polymerization

Question 14

Which equation describes the treadmilling phenomenon in actin filaments?

Accepted Answer

$$r_{+} \u003e r_{-} at $$the plus end, $$r_{-} \u003e r_{+} at $$the minus end$

Question 15

Which cytoskeletal element is most important for axon strength and size determination in neurons?

Accepted Answer

Neurofilaments (Class IV intermediate filaments)

Question 16

Which scenario best illustrates the function of microtubule organizing centers (MTOCs) in animal cells?

Accepted Answer

Formation of the mitotic spindle during cell division

Question 17

Which drug would most likely prevent the addition of new actin monomers to microfilaments?

Accepted Answer

Cytochalasin D

Question 18

Which equation best represents the relationship between the rate of microtubule polymerization and tubulin concentration?

Accepted Answer

$$Rate = k_{on} [Tubulin]$$

Question 19

Which cytoskeletal element is most likely to be disrupted in a patient with a mutation in keratin genes?

Accepted Answer

Intermediate filaments

Question 20

Which process is most directly dependent on the dynamic instability of microtubules?

Accepted Answer

Chromosome segregation during mitosis

Cytoskeletal Systems and Cellular Motility: Microtubules, Microfilaments, and Intermediate Filaments

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