6. Which of the following statements about molecular switches is false? A) Prote
ID: 265515 • Letter: 6
Question
6. Which of the following statements about molecular switches is false? A) Protein kinases transfer the terminal phosphate from ATP onto a protein B) Some kinases alter another kinase enzyme. C) A GTP-binding protein exchanges its bound GDP for GTP to become activated D) Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them 'off. E) Binding phosphate changes protein conformation. 7. Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant INSIDE a typical mammalian cell? A) Na B) K D) Cl E) H20 8. Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K' channel in the plasma membrane. Which of the following would enhance this effect of the acetylcholine? A addition of a drug that prevents the a subunit from exchanging GDP for GTP B) mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein c addition of a high concentration of a nonhydrolyzable analog of D) mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine E) addition of a high concentration of ATP 9. Which one of the following binds calcium ions in a smooth muscle causing contraction? A) Myosin B) Troponin C) Tropomyosin Calmodulin E) Actin 10. When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a A) hormone. B) dissolved gas. C) G-protein D neurotransmitter paracrine 11. Which of the following is required for the secretion of neurotransmitters in response to an action potential? A) Na*-K' pumps B) voltage-gated Ca2 channels C) neurotransmitter receptors D) voltage-gated K' channels E) GPCRsExplanation / Answer
6. d. Phosphatases remove the phosphate from GTP on GTP binding proteins, turning them off.
7. b. K+
8. c. addition of a high concentration of non ionizable analog of GTP.
9. d. calmodulin
10. a. hormone
11. b. voltage gated Ca2+ channels
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