Unit 3: Cytoskeleton and Nucleus - Practice Quiz

1 What is the basic protein subunit of a microtubule?

2 Which cellular structure is commonly organized by microtubules?

3 Which motor protein generally moves cargo toward the plus end of a microtubule?

4 What is one important function of microtubules during cell division?

5 Which cytoskeletal filament is usually the thinnest?

6 What is a major function of intermediate filaments?

7 Which protein is the main component of actin filaments?

8 Which motor protein interacts directly with actin filaments?

9 Actin filaments are especially important in which process?

10 How many membranes make up the nuclear envelope?

11 What is the main function of a nuclear pore complex?

12 Nuclear pore complexes are embedded in which structure?

13 What is the central passageway of a nuclear pore complex used for?

14 The nuclear lamina is located mainly on which side of the nuclear envelope?

15 Which proteins form the main structural network of the nuclear lamina?

16 What is one function of the nuclear lamina?

17 What signal directs many proteins into the nucleus?

18 Which transport receptor commonly carries proteins into the nucleus?

19 What signal is commonly required for nuclear protein export?

20 Which small GTPase helps provide directionality for nuclear transport?

21 A drug prevents tubulin subunits from adding to microtubule plus ends. Which cellular process would be most directly impaired?

22 A cell treated with a compound that prevents GTP hydrolysis in tubulin would most likely show which effect?

23 A motor protein moves cargo toward the microtubule-organizing center in an axon. Which motor is most likely responsible?

24 If centrosome function is disrupted in a dividing animal cell, which defect is most likely?

25 A mutation weakens keratin filament connections between epithelial cells. Which tissue-level consequence is most likely?

26 A migrating cell cannot form branched actin networks at its leading edge. Which process would be most directly affected?

27 A toxin prevents actin filament depolymerization but does not block polymerization. What is the likely cellular outcome?

28 A cell has normal actin polymerization but defective myosin II activity. Which event would be most impaired?

29 Which feature best explains why intermediate filaments are especially useful for resisting mechanical stress?

30 A mutation removes a nucleoporin that forms part of the central transport channel. Which consequence is most likely?

31 Why can small ions pass through nuclear pore complexes more freely than large protein complexes?

32 A defect prevents nuclear pore complexes from being inserted into the double membrane of the nuclear envelope. Which structure would be directly affected?

33 A mutation reduces lamin filament assembly. Which nuclear defect would be most likely?

34 During mitosis, phosphorylation of nuclear lamins promotes which event?

35 A cell expresses a lamin variant that cannot be properly modified after translation. Which process may be disrupted during cell division?

36 A protein containing a functional nuclear localization signal is synthesized in the cytoplasm. Which factor typically recognizes this signal?

37 A nuclear protein remains in the cytoplasm even though its nuclear localization signal is intact. A mutation in which factor could explain this result?

38 A newly synthesized RNA-binding protein must leave the nucleus after binding an export receptor. Which signal would most directly support this transport?

39 A transcription factor is retained in the cytoplasm when a signaling pathway keeps it bound to an inhibitory protein. How does this regulation work?

40 Why is the Ran-GTP/Ran-GDP gradient important for directional nuclear transport?

41 A cell expresses a tubulin mutant that retains GTP binding but cannot hydrolyze tubulin-bound GTP after polymerization. Which phenotype is most likely?

42 A drug selectively prevents microtubule minus ends from being anchored at centrosomes but does not affect tubulin polymerization. Which consequence is most likely in a migrating animal cell?

43 A vesicle normally transported toward the cell center continues moving after dynein inhibition but accumulates near the cell cortex. Which interpretation best explains the result?

44 A mitotic cell is treated with a compound that suppresses microtubule catastrophe but leaves kinetochore attachment intact. Which defect is most likely?

45 A keratin mutation prevents formation of stable lateral interactions between keratin tetramers but does not affect keratin expression. Which cellular property is most directly compromised?

46 A nonhydrolyzable ATP-actin analog is incorporated into a growing filament. Compared with normal actin, what is the most likely effect?

47 A cell has normal actin polymerization but lacks functional profilin. Which process is most likely impaired under conditions requiring rapid filament growth?

48 A migrating cell expresses a constitutively active cofilin phosphatase. Which outcome is most likely if cofilin remains persistently active?

49 A mutation removes the cytoplasmic filaments of the nuclear pore complex but leaves the central channel intact. Which defect is most likely?

50 A nuclear pore complex retains its scaffold but has altered phenylalanine-glycine-rich nucleoporins that no longer form a selective permeability barrier. Which result is expected?

51 A cell contains normal nuclear pores but develops a mutation that prevents fusion of the inner and outer nuclear membranes at pore sites. What is the direct consequence?

52 A lamin mutant cannot be phosphorylated during mitosis but retains normal polymerization in interphase. Which phenotype is most likely?

53 A mutation weakens lamin attachment to chromatin without changing lamin abundance. Which nuclear defect is most plausible?

54 A nucleus has a mechanically defective lamina but normal nuclear pores and normal chromatin composition. Which cellular response is most likely after repeated mechanical stress?

55 A nuclear protein contains a functional nuclear localization signal, but its import receptor cannot bind Ran-GTP. Which outcome is most likely?

56 A protein lacking a classical nuclear localization signal is nevertheless imported efficiently when bound to a partner containing such a signal. What mechanism explains this result?

57 A nuclear export cargo binds its export receptor only in the presence of Ran-GTP. If Ran-GTP is experimentally depleted from the nucleus, what happens first?

58 A transcription factor is phosphorylated near its nuclear localization signal, reducing importin binding. What regulatory outcome is most likely?

59 A signaling pathway inhibits the cytoplasmic Ran-GAP while leaving nuclear Ran-GEF active. Which change is expected in the Ran system?

60 A nuclear export signal is exposed only after ligand binding causes a conformational change in a regulatory protein. Which prediction is most appropriate?