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5.1 Microtubules — Test 1
Q1. Microtubules are composed of:✓ Tubulin
Q2. In eukaryotic flagella, the arrangement of microtubules in the axoneme is:✓ 9 + 2
Q3. The typical arrangement of a motile cilium is:✓ 9+2 with a pair of dynein arms on outer doublets containing 13 protofilaments
Q4. Colchicine-treated cells are arrested in:✓ Metaphase
Q5. Colchicine is a chemical which:✓ Prevents microtubule polymerization
Q6. Taxol acts by:✓ Stabilizing microtubules
Q7. The primary function of the centrosome's microtubule-organizing centre (MTOC) is:✓ Microtubule nucleation
Q8. Kinesin motors move along:✓ Microtubules
Q9. Which one of the following is NOT a molecular motor?✓ Dynamin
Q10. Which statement is NOT correct about tubulin?✓ α-tubulin hydrolyzes its bound GTP
Q11. All of the following structures are made up of tubulin EXCEPT:✓ Lamellipodia
Q12. A loss-of-function mutation in the γ-tubulin gene is most likely to:✓ Inhibit microtubule nucleation at the centrosome
5.2 Microfilaments (Actin) — Test 2
Q13. Phalloidin affects which of the following structures?✓ Microfilaments
Q14. Phalloidin is an inhibitor of actin that works by:✓ Stabilizing the filaments (preventing depolymerization)
Q15. Cytochalasin D inhibits microfilament formation. Which of the following activities will NOT be hindered?✓ Cytosolic transport of vesicles
Q16. The rapid plus-end (barbed-end) growth of an actin polymer depends on monomers binding to:✓ Profilin
Q17. The molecular mechanism behind amoeboid locomotion via pseudopodia involves:✓ Activation of formins
Q18. ADF/cofilin increases actin turnover by regulating the actin filament's:✓ Severing
Q19. Which protein is involved in cross-linking actin filaments?✓ α-Actinin
Q20. Actin filaments are found in all of the following EXCEPT:✓ Flagella of bacteria
Q21. Cytochalasin B added just before mitosis begins is most likely to:✓ Allow mitosis to complete but arrest at cytokinesis
Q22. Which molecule depresses cardiac contractility by disrupting F-actin?✓ Cytochalasin D
5.3 Intermediate Filaments — Test 3
Q23. Desmin filaments are found in:✓ Muscle cells
Q24. The major structural protein underlying the nuclear envelope is:✓ Lamin
Q25. Which protein links actin to intermediate filaments in a cell?✓ Plectin
Q26. Lamin proteins are present in which compartment of the cell?✓ Nucleus
Q27. Which intermediate-filament protein is characteristic of epithelial cells?✓ Keratin
Q28. Defective cleavage of prelamin A to lamin A on the nuclear membrane causes:✓ Progeria
5.4 Cytoskeletal Organization — Test 4
Q29. The cytoskeleton of eukaryotic cells is formed by:✓ Protein filaments
Q30. The actin-binding protein that forms a flexible bridge between two actin filaments at various angles is:✓ Filamin
Q31. Which combination correctly matches each cytoskeletal filament to its main function?✓ Intermediate filaments → mechanical strength; microtubules → tracks for motors; actin → cell locomotion
Q32. Which protein links the actin cytoskeleton to the plasma membrane, forming the membrane skeleton of red blood cells?✓ Spectrin
Q33. A motor protein that walks along microtubules toward the minus end is:✓ Dynein
Q34. Tau, which forms neurofibrillary tangles when hyperphosphorylated, is basically a:✓ Microtubule-associated protein (MAP)