Q: Which of the following equations correctly represents the nucleotide hydrolysis required for actin polymerization?

$\mathrm{G\text{-}actin} + \mathrm{ATP} \rightarrow \mathrm{F\text{-}actin} + \mathrm{ADP}$

Question 1

Which of the following statements best describes the primary function of the cytoskeleton in eukaryotic cells?

Accepted Answer

It is a dynamic network of protein filaments that supports cell shape, enables movement, and organizes intracellular transport.

Question 2

Microtubules are assembled from heterodimers of which two proteins, and what nucleotide is required for their polymerization?

Accepted Answer

Alpha- and beta-tubulin; GTP

Question 3

A researcher treats dividing cancer cells with vincristine. What is the most likely cellular effect of this drug?

Accepted Answer

It inhibits microtubule polymerization, disrupting spindle formation and arresting cell division.

Question 4

Which cytoskeletal component is most directly involved in the formation of the contractile ring during cytokinesis?

Accepted Answer

Microfilaments (actin)

Question 5

A patient presents with Kartagener syndrome, characterized by situs inversus and chronic respiratory infections. Which cytoskeletal motor protein is most likely mutated?

Accepted Answer

Dynein

Question 6

Which of the following best explains why microvilli increase nutrient absorption in intestinal cells?

Accepted Answer

They are supported by parallel bundles of microfilaments, increasing surface area for absorption.

Question 7

During axon growth in neurons, which cytoskeletal elements are most important for extending the growth cone?

Accepted Answer

Microtubules and microfilaments

Question 8

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

Accepted Answer

Microfilaments are composed of actin and have polarity, while intermediate filaments are composed of various proteins and lack polarity.

Question 9

A mutation in the gene encoding desmin is most likely to affect which tissue?

Accepted Answer

Muscle tissue

Question 10

Which process is most directly dependent on the ATP-dependent interaction between actin and myosin?

Accepted Answer

Muscle contraction

Question 11

Which cytoskeletal structure is responsible for the coordinated beating of cilia in respiratory epithelial cells?

Accepted Answer

Axonemal microtubules arranged in a 9+2 pattern

Question 12

Which signaling proteins are most important for regulating cytoskeletal dynamics in response to extracellular signals?

Accepted Answer

Rho, Rac, CDC42

Question 13

A cell is observed to extend a pseudopodium and crawl forward. Which cytoskeletal element is primarily responsible for this type of movement?

Accepted Answer

Microfilaments (actin)

Question 14

Which of the following best describes the assembly of intermediate filaments?

Accepted Answer

Monomers assemble into dimers, which align laterally into tetramers, then into protofilaments.

Question 15

Which cytoskeletal component is most often used as a diagnostic marker in cancer pathology due to its cell-type specificity?

Accepted Answer

Intermediate filaments

Question 16

Which of the following equations correctly represents the nucleotide hydrolysis required for actin polymerization?

Accepted Answer

$\mathrm{G	ext{-}actin} + \mathrm{ATP} ightarrow \mathrm{F	ext{-}actin} + \mathrm{ADP}$

Question 17

Which cytoskeletal element is most critical for the mechanical linkage of epithelial cells via adherens junctions?

Accepted Answer

Microfilaments (actin)

Question 18

A cell is unable to segregate its chromosomes during mitosis. Which cytoskeletal structure is most likely defective?

Accepted Answer

Mitotic spindle microtubules

Question 19

Which of the following best explains the effect of taxanes on microtubules in cancer therapy?

Accepted Answer

They stabilize microtubules, preventing their depolymerization and blocking mitosis.

Question 20

Which intermediate filament protein is most likely to be upregulated during epithelial-to-mesenchymal transition (EMT) in cancer progression?

Accepted Answer

Vimentin

The Cytoskeleton: Structure, Components, and Functions in Eukaryotic Cells

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