Lodish8e_Ch18_TestBank PDF

18 - 1 18 Cell Organization and Movement II: Microtubules and Intermediate Filaments Section 18.1 1. A microtubule protofilament is formed by the: a. lateral association of onlyg-tubulin subunits. b. head-to-tail association of only g-tubulin subunits. c. lateral association of tubulin dimer...

18 - 1 18 Cell Organization and Movement II: Microtubules and Intermediate Filaments Section 18.1 1. A microtubule protofilament is formed by the: a. lateral association of onlyg-tubulin subunits. b. head-to-tail association of only g-tubulin subunits. c. lateral association of tubulin dimers. d. head-to-tail association of tubulin dimers. Ans: d Question Type: Multiple choice Chapter 18.1 Blooms: Understanding Difficulty: Moderate 2. In cells, the g-tubulin ring complex is found: a. in the hollow core of the microtubule. b. at the microtubule (−) end. c. at the microtubule (+) end. d. along the outer wall of the microtubule. Ans: b Question Type: Multiple choice Chapter 18.1 Blooms: Understanding Difficulty: Moderate 3. In most cells, where do all microtubules originate? Ans: In most cells, microtubules originate from the MTOC, and the minus ends of the microtubules nucleated by this structure usually remain associated with the MTOC. Question Type: Essay Chapter 18.1 Blooms: Remembering Difficulty: Easy 4. What is a microtubule protofilament? Ans: A microtubule protofilament is a head-to-tail assembly of tubulin dimers. Thirteen such structures compose the cylindrical wall of the microtubule. Question Type: Essay Chapter 18.1 Blooms: Understanding Difficulty: Easy 5. The alpha and beta tubulin proteins can bind: a. to ATP or ADP. b. to GTP or GDP. c. only to GDP. d. none of the above Ans: d Question Type: Multiple choice Chapter 18.1 Blooms: Remembering Difficulty: Easy 6. Where are microtubules observed to be present in different polarities? a. axons of nerve cells b. animal cells in interphase c. animal cells in mitosis d. dendrites of nerve cells Ans: d Question Type: Multiple choice Chapter 18.1 Blooms: Remembering Difficulty: Easy Section 18.2 7. At MTOCs, microtubule nucleation is facilitated by: a. centrioles. b. g-tubulin. c. GDP-tubulin dimers. d. basal bodies. Ans: b Question Type: Multiple choice Chapter 18.2 Blooms: Remembering Difficulty: Easy 8. Growing microtubule ends are normally stabilized by: a. a GDP cap. b. a GTP cap. c. phosphorylation of tubulin subunits. d. g-tubulin. Ans: b Question Type: Multiple choice Chapter 18.2 Blooms: Understanding Difficulty: Easy 9. The drug taxol acts to: a. block microtubule assembly. b. stabilize microtubules against depolymerization. c. promote cell division. d. sever microtubules. Ans: b Question Type: Multiple choice Chapter 18.2 Blooms: Remembering Difficulty: Moderate 10. What happens to a microtubule that loses its GTP cap? Ans: Loss of the GTP cap will cause a microtubule to convert from growth to shortening. Shortening will continue until the microtubule disappears or a new cap forms. Question Type: Essay Chapter 18.2 Blooms: Blooms: Applying Difficulty: Moderate 11. What are the effects of colchicine and taxol on cells? Ans: Colchicine blocks assembly of the cell’s microtubules; taxol stabilizes the cell’s tubulin in polymer form. In either case, the normal microtubule dynamics will be disrupted, and the cells will be unable to divide. Question Type: Essay Chapter 18.2 Blooms: Blooms: Applying Difficulty: Moderate 12. A drug that prevents microtubules from depolymerizing could be used to: a. stimulate cytokinesis. b. inhibit mitosis. c. promote cell division. d. treat Alzheimer’s disease. Ans: b Question Type: Multiple choice Chapter 18.2 Blooms: Blooms: Applying Difficulty: Easy Section 18.3 13. Microtubule assembly requires: a. microtubule-associated proteins. ° b. incubation at 4 C. c. ATP. d. a tubulin concentration in excess of the Cc. Ans: d Question Type: Multiple choice Chapter 18.3 Blooms: Understanding Difficulty: Moderate 14. MAP2 and Tau are examples of microtubule: a. destabilizing proteins. b. motor proteins. c. nucleating proteins. d. stabilizing proteins. Ans: d Question Type: Multiple choice Chapter 18.3 Blooms: Remembering Difficulty: Easy 15. The EB1 protein has several functions. Which of the following is/are true regarding EB1? a. It promotes microtubule growth by enhancing polymerization at the (+) end. b. Other microtubule plus-end tracking proteins use EB1 to “hitchhike” onto the growing microtubule. c. It can bind further back from the blunt end of microtubules. d. all of the above Ans: d Question Type: Multiple choice Chapter 18.3 Blooms: Understanding Difficulty: Difficult 16. Which of the following is NOT a way in which a microtubule switches from growing to shortening? a. loss of GTP cap b. treatment with colchicine c. binding of MAP2 d. binding of stathmin Ans: b Question Type: Multiple choice Chapter 18.3 Blooms: Understanding Difficulty: Easy Section 18.4 17. The region of a motor protein that interacts with the motor’s cellular cargo is the: a. head domain. b. tail domain. c. rod domain. d. light chains. Ans: b Question Type: Multiple choice Chapter 18.4 Blooms: Remembering Difficulty: Easy 18. All of the following statements describe kinesin-I EXCEPT: a. kinesin-I is a (−) end-directed motor. b. kinesin-I transports vesicles along microtubules. c. kinesin-I binds and hydrolyzes ATP to produce movement. d. kinesin-I is composed of two heavy chains and two light chains. Ans: a Question Type: Multiple choice Chapter 18.4 Blooms: Blooms: Applying Difficulty: Moderate 19. The _____ serves as a template for the unusual structure of axoneme microtubules. a. g-tubulin ring complex b. pericentriolar material c. centrosome d. basal body Ans: d Question Type: Multiple choice Chapter 18.4 Blooms: Remembering Difficulty: Easy 20. For kinesin motors, the direction of movement along a microtubule is specified by the motor’s: a. motor (head) domain. b. neck region. c. stalk domain. d. tail domain. Ans: b Question Type: Multiple choice Chapter 18.4 Blooms: Remembering Difficulty: Easy 21. Which of the following is true regarding the transport of cargo by cytoplasmic dynein? a. Dynactin is the protein that links dynein to microtubules. b. Transport is toward the (+) end of the microtubules. c. GTP binds to the head region of dynein. d. LIS1 associates with the head region of dynein to facilitate transport. Ans: d Question Type: Multiple choice Chapter 18.4 Blooms: Understanding Difficulty: Moderate 22. Why would neuronal vesicles probably contain both kinesin and cytosolic dynein? Ans: Neuronal vesicles may contain both motors to allow the vesicle to travel in either direction along a microtubule. Kinesin can carry the vesicle from the cell body to the axon terminus, while dynein can carry the vesicle back to the cell body. Question Type: Essay Chapter 18.4 Blooms: Analyzing Difficulty: Moderate 23. What effect will addition of AMP-PNP have on axonal transport? Ans: AMP-PNP induces tight binding of kinesin (and most other microtubule motors) to microtubules; therefore, vesicle transport would cease because the motors would be locked onto the microtubules. Question Type: Essay Chapter 18.4 Blooms: Analyzing Difficulty: Difficult Section 18.5 24. The force for axoneme bending is derived from the: a. sliding movement of central pair microtubules. b. contraction of central pair microtubules. c. sliding movement of outer doublet microtubules. d. contraction of outer doublet microtubules. Ans: c Question Type: Multiple choice Chapter 18.5 Blooms: Understanding Difficulty: Easy 25. The primary cilium: a. is nonmotile because it lacks the “central pair” of microtubules. b. is relatively susceptible to microtubule destabilizing drugs like colchicine. c. has no known role in humans. d. none of the above Ans: a Question Type: Multiple choice Chapter 18.5 Blooms: Understanding Difficulty: Moderate 26. What motor protein generates the force to cause axoneme bending? Ans: Outer arm axonemal dynein generates the sliding of outer doublets relative to each other, and it is this movement that ultimately produces axoneme bending. Question Type: Essay Chapter 18.5 Blooms: Remembering Difficulty: Moderate 27. What is the role of the basal body in generating axoneme structure? Ans: The basal body is a bundle of nine triplet microtubules. Two tubules of each triplet (the A and the B tubules) act as a template for tubulin assembly and the generation of the A and B tubules of the axoneme. Question Type: Essay Chapter 18.5 Blooms: Understanding Difficulty: Easy 28. Which of the following is NOT true about cilia? a. All cilia arise from nine sets of outer triplet microtubules (similar to centrioles). b. Cilia contain the same transport system as flagella, called IFT. c. All cells with cilia are motile because of the axonemal dynein motor. d. Primary cilia contain receptors that increase the cell’s responsiveness to its environment. Ans: c Question Type: Multiple choice Chapter 18.5 Blooms: Understanding Difficulty: Moderate Section 18.6 29. Separation of spindle poles during spindle formation and anaphase B most likely depends on which of the following? a. (+) end-directed microtubule motors at the cell cortex b. (+) end-directed microtubule motors at the kinetochore c. (−) end-directed microtubule motors in the microtubule overlap zone d. (+) end-directed microtubule motors in the microtubule overlap zone Ans: d Question Type: Multiple choice Chapter 18.6 Blooms: Understanding Difficulty: Easy 30. Which of the following occurs during anaphase A? a. The spindle elongates. b. Kinetochores remain attached to shortening kinetochore microtubules. c. Chromosomes move to the spindle equator. d. The spindle poles move closer together. Ans: b Question Type: Multiple choice Chapter 18.6 Blooms: Remembering Difficulty: Moderate 31. In the mitotic spindle, astral microtubules function to: a. connect the spindle poles. b. attach chromosomes to the spindle. c. carry out cytokinesis. d. anchor the spindle poles to the plasma membrane. Ans: d Question Type: Multiple choice Chapter 18.6 Blooms: Understanding Difficulty: Moderate 32. Treadmilling through kinetochore microtubules can be observed by: a. simple fluorescence microscopy. b. optical trap microscopy. c. fluorescence speckle microscopy. d. electron microscopy. Ans: c Question Type: Multiple choice Chapter 18.6 Blooms: Remembering Difficulty: Easy 33. Kinetochores assemble at the: a. centrosome. b. spindle pole. c. telomere. d. centromere. Ans: d Question Type: Multiple choice Chapter 18.6 Blooms: Remembering Difficulty: Easy 34. Capture of microtubule (+) ends by chromosomes occurs during: a. metaphase. b. prometaphase. c. anaphase. d. telophase. Ans: b Question Type: Multiple choice Chapter 18.6 Blooms: Remembering Difficulty: Easy 35. Poleward movement of chromosomes during anaphase A requires: a. microtubule polymerization. b. ATP. c. kinetochore motor proteins. d. BimC. Ans: c Question Type: Multiple choice Chapter 18.6 Blooms: Understanding Difficulty: Easy 36. What function do kinetochore-bound motor proteins perform during anaphase A? Ans: During anaphase A, kinetochore-bound motor proteins are thought to maintain kinetochore attachment to shortening kinetochore microtubules. Question Type: Essay Chapter 18.6 Blooms: Understanding Difficulty: Easy 37. What role do astral microtubules play in spindle elongation? Ans: Astral microtubules may serve as “ropes” by which (−) end-directed microtubule motors at opposite sides of the cell cortex reel in the spindle poles and thereby produce spindle elongation. Question Type: Essay Chapter 18.6 Blooms: Understanding Difficulty: Easy 38. During late anaphase and telophase, the microfilament-based contractile ring facilitates pinching the cell into two, but the ring must first be positioned equidistant between the two spindle poles before this occurs. Describe the mechanism whereby signals from the spindle direct the positioning of the contractile ring. Ans: The chromosome passenger complex (CPC) is part of the signal responsible for regulating microtubule attachment to kinetochores during pro-metaphase. At anaphase the CPC leaves the centromeres and becomes associated with polar microtubules at the spindle center. Here, the CPC recruits the centralspindlin protein complex which includes a kinesin motor protein that concentrates at the middle of the spindle. Later, during anaphase B, centralspindlin recruits a RhoA exchange factor, which exchanges GDP for GTP on RhoA. RhoA, in this GTP-bound state, then activates a formin protein to drive the nucleation of actin into the microfilaments that make up the ring. Thus, the spindle position directly serves to delineate where the contractile ring must form to properly complete cytokinesis. Question Type: Essay Chapter 18.6 Blooms: Blooms: Applying Difficulty: Difficult Section 18.7 39. Which of the following does NOT belong to the intermediate filament protein family? a. vimentin b. keratin c. laminin d. desmin Ans: c Question Type: Multiple choice Chapter 18.7 Blooms: Remembering Difficulty: Easy 40. During mitosis, the breakdown of the nuclear envelope depends on the disassembly of lamin filaments that form a meshwork supporting the membrane. How is that breakdown accomplished? Ans: Phosphorylation of nuclear lamins by a cyclin-dependent kinase active in early mitosis induces their disassembly and prevents their reassembly until the phosphates are removed later in mitosis by specific phosphatases. Question Type: Essay Chapter 18.7 Blooms: Understanding Difficulty: Moderate 41. The important role that intermediate filaments play in the epithelial cells of the skin is evident in which of the following? a. Individual keratin filaments span the cell membrane and directly connect one cell to the next. b. Knockout mice for a keratin gene like K14 exhibit stronger skin that can withstand abrasion. c. The polarity of keratin filaments allows them to withstand shear stress. d. Patients with mutations in keratin genes exhibit skin problems. Ans: d Question Type: Multiple choice Chapter 18.7 Blooms: Understanding Difficulty: Moderate 42. Which of the following is true about intermediate filaments? a. They are named based on their location in cells between actin microfilaments and microtubules. b. All cells express the same class II cytoplasmic intermediate filament proteins. c. Staggered, antiparallel tetramers give intermediate filaments strength. d. Acidic and basic keratins provide dynamic paths on which organelles may travel. Ans: c Question Type: Multiple choice Chapter 18.7 Blooms: Understanding Difficulty: Moderate Section 18.8 43. In studies of wound healing, it was noticed that when the cells at the edge are induced to polarize and move to fill the wound, the Golgi complex moves to the front of the nucleus toward the cell front. What is the purpose of this reorientation and how is it accomplished? Ans: Cdc42 activation at the front of the cell binds to the polarity factor Par6. This initiates a series of interactions that recruits the dynein-dynactin complex to the front of the cell. The dynein-dynactin complex pulls microtubules to orient the centrosome toward the front of the cell. This microtubule reorientation serves to polarize the secretory pathway toward the front of the cell to allow for the delivery of adhesion molecules. Question Type: Essay Chapter 18.8 Blooms: Blooms: Applying Difficulty: Difficult