20- Which of the conditions below might decrease the likelihood for a skeletal m
ID: 269528 • Letter: 2
Question
20- Which of the conditions below might decrease the likelihood for a skeletal muscle to contract? a. Partial depolarization of the T-tubule membrane. b. Addition of a drug that blocks tropomyosin binding to actin. c. Addition of a drug that blocks calcium binding to troponin. d. An increase in the amount of ATP in the cell. e. A mutation in tropomyosin that decreases its affinity for the actin filament 21- Which of the following is an incorrect match? a GTP binding ? switches on a G protein. b, Protein kinase ? switches ON a phospho protein. c. Protein phosphatase ? switches off a phospho protein. d. GDP phosphory lation switches ON a G protein e. ATP ? Donates phosphate to proteins. 22- In the GPCR signaling pathway, the production of cAMP by the adenylyl cyclase is a. b. c. d- e. An amplification step. An integration step. A distribution step. The cellular response. An inactivation step. 23- Which of the following can play the role of SECOND MESSENGER in the pathway downstream of adenylyl cyclase? a. IP3 b. DAG ?. CAMP. d. All of the above. e. "a" and "b" only. 24- Which of the following can play the role of SECOND MESSENGER in a pathway downstream of the G-protein coupled receptor? a. IP3 b. DAG c. CAMP All of the above. "a" and "to", only. d. e. 25- Which of the following is observed during the activation of a signaling pathway initiated by a growth factor that binds a GPCR? a. Receptor dimerization. b. Receptor phosphorylation. c. Activation of trimeric G proteins. d. Activation of a monomeric G protein. e. All of the above 26- In signaling pathways, molecular switches might be a. lons channels b. G proteins c. Phospho proteins d. ..b" and "e" e. "a" and e".Explanation / Answer
20. For a skeletal muscle to contract, Ca2+ must bind to troponin. So if there is a drug that prevent this binding, the signal is not conducted properly, resulting in decreased likelihood of skeletal muscle contration.
ANSWER: c.
21. In GPCR signalling, GTP binding activates G-protein, protein kinase activates phosphoprotein, phosphatase deactivates phosphoprotein, GDP inactivates G-protein. ATP serves as a phosphate donor. The incoorect pair is the GDP biniding and switching on of G-protein
ANSWER: d.
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