Exam3 - Cell Biology / Cell Biochemistry Exam 3 Nov 2, 2009...

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Cell Biology / Cell Biochemistry Exam 3 Nov 2, 2009 Chose the single best answer to each of the following questions. Read each question carefully . In some cases, key words are emphasized in bold italics font. 1. Which of the following events usually terminates muscle contraction ? a. ATP levels are exhausted b. calcium ions are transported back into the sarcoplasmic reticulum c. myosin head groups are phosphorylated by myosin light chain kinase d. acetylcholine is degraded by acetylcholine esterase e. sodium channels inactivate 2. Which of the following toxins binds to and stabilizes microtubules ? a. cytochalasin B b. taxol c. colchicine d. phalloidin e. vinblastin 3. Which of the following toxins binds to and stabilizes actin filaments ? a. cytochalasin B b. taxol c. colchicine d. phalloidin e. vinblastin 4. In the laboratory, you have shown that activation of a novel GPCR increases phospholipase C activity, and that this effect is blocked by pertussis toxin. This GPCR is probably signaling through which of the following G-proteins? a. Gs d. Gt (transducin) b. Gi e. Ras c. Go 5. Which of the following proteins releases calcium from the sarcoplasmic reticulum in response to muscle depolarization? a. a voltage-gated calcium channel b. a calcium-gated calcium channel c. an M-type calcium ATPase d. a sodium-calcium antiporter e. an IP3 receptor 6. During which phase of the cell cycle does most cell growth occur? a. G1 phase b. S phase c. G2 phase d. M phase e. cell growth occurs throughout the cell cycle 7. The gaseous messenger, nitric oxide, is produced by nitric oxide synthase from which of the following precursors. a. asparagine
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b. arginine c. alanine d. nitrate e. nitrous oxide 8. Cholera toxin disrupts cell biochemistry by covalently modifying the alpha subunit of which of the following trimeric G proteins? a. Gs d. Gq b. Gi e. none of the above c. Go 9. Signaling through a G-protein coupled receptor most often results in which of the following? a. activation of a membrane-associated enzyme b. alteration in gene expression c. reorganization of the cytoskeleton d. calcium mobilization e. none of the above 10. During signaling through a G-protein coupled receptor, which event inactivates the alpha subunit of the trimeric G-protein? a. ATP hydrolysis b. GTP hydrolysis c. binding to the beta-gamma complex d. dissociation from the beta-gamma complex e. exchange of GDP for GTP 11. On which of the following cell membranes would you expect to find inositol 1,4,5-tris phosphate (IP3) receptors? a. the plasma membrane b. the mitochondrial outer membrane c. the nuclear envelope d. the smooth endoplasmic reticulum e. the Golgi complex 12. During embryonic development, the fate of uncommitted cells is often determined by their location along an extracellular gradient of a diffusible “morphogen”. This is an example of which of the following signaling strategies? a. endocrine signaling
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Exam3 - Cell Biology / Cell Biochemistry Exam 3 Nov 2, 2009...

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