Selected MCQ

Current Question
Which cytoskeletal filament requires ATP hydrolysis for its polymerization?
  • A. Microtubules
  • B. Actin microfilaments
  • C. Intermediate filaments
  • D. Cellulose microfibrils
Correct Answer: B
Explanation:
Actin polymerization uses ATP. Microtubules use GTP for tubulin assembly; intermediate filaments do not use nucleotide hydrolysis.
Related Question 1
Crawling movement of cells (e.g., fibroblasts) primarily depends on the polymerization of which cytoskeletal component?
  • A. Microtubules
  • B. Intermediate filaments
  • C. Actin microfilaments
  • D. Centrioles
Correct Answer: C
Explanation:
Lamellipodia and filopodia are actin-based protrusions. Actin polymerization at the leading edge drives cell crawling and motility.
Related Question 2
One major difference between intermediate filaments and microtubules is that intermediate filaments:
  • A. Contain α- and β-tubulin
  • B. Are polar structures
  • C. Degrade in the absence of ATP
  • D. Lack structural polarity
Correct Answer: D
Explanation:
Intermediate filaments are apolar (no distinct plus/minus ends) and do not require nucleotide hydrolysis for polymerization.
Related Question 3
Which type of endocytosis involves clathrin-coated pits and often requires receptor binding?
  • A. Phagocytosis
  • B. Pinocytosis
  • C. Receptor-mediated endocytosis
  • D. Exocytosis
Correct Answer: C
Explanation:
Receptor-mediated endocytosis uses clathrin-coated vesicles. Specific ligands bind membrane receptors, concentrating them in coated pits for internalization.
Related Question 4
Which cytoskeletal element is directly involved in separating sister chromatids during anaphase of mitosis?
  • A. Actin filaments (microfilaments)
  • B. Intermediate filaments
  • C. Microtubules of the mitotic spindle
  • D. Myosin thick filaments
Correct Answer: C
Explanation:
Kinetochore microtubules shorten during anaphase, pulling sister chromatids apart. Actin and myosin are involved in cytokinesis, not chromatid separation.
Related Question 5
Actin filaments (microfilaments) participate in all the following processes except:
  • A. Muscle contraction via interaction with myosin
  • B. Formation of the cleavage furrow during cytokinesis
  • C. Rapid, long-range vesicle transport along axons via kinesin
  • D. Structural support of microvilli in intestinal epithelial cells
Correct Answer: C
Explanation:
Actin is key in muscle contraction, cytokinesis, and microvilli structure. Kinesin motors move along microtubules, not actin, for long-range vesicle transport.