help A marathon runner is several hours into a race. His metabolism is dominated

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help A marathon runner is several hours into a race. His metabolism is dominated by the influence of epinephrine and glucagon's. Which of the following enzymes is likely to be and active in the liver and muscle tissue? A) glycogen synthase B) pyruvate dehydrogenase C) HMG CoA reductase D) glycogen phosphorylase E) fatty acyl transferase Cyanide, oligomycin, and 2, 4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation. Which of the following statements correctly describes the mode of action of the three inhibitors? A) Cyanide and 2, 4-dinitrophenol inhibit the respiratory chain, and inhibits the synthesis of ATP. B) Cyanide inhibits the respiratory chain, whereas and 2, 4-dinitrophenol inhibit the synthesis of ATP. C) Cyanide, , and 2, 4-dinitrophenol compete with O_3, for cytochrome oxidase (Complex IV). D) Oligomycin and cyanide inhibit synthesis of ATP: 2, 4-dinitrophenol inhibits the respiratory chain. E) Olgomycin inhibits the respiratory chain, whereas cyanide and 2, A-dinitrophenol prevent the synthesis of ATE The standard reduction potentials (E") for the following half reactions are given. + 2H' + 2e^- rightarrow succinate E" = +0.031 V FAD + 2H^+ + 2e^- rightarrow FADH_2 E" = -0.219 V If succinate, , FAD, and FADH, all at I M concentrations, were mixed together in the presence of dehydrogenase, which of the following would happen initially? A) Fumarate and succinate would become oxidized: FAD and FADH2 would become reduced. B) Succinate would become oxidized: FAD would become reduced. C) No reaction would occur because all reactants and products are already at their standard concentration D) Succinate would become oxidized: FADH_2 would be unchanged because it is a cofactor, not a substrate. E) Fumarate would become reduced: FADH_2 would become oxidized. Proteins are effective buffers over a wide range of pHs because they usually contain: A) a large number of amino acids B) a large number of hydrogen bonds in alpha-helices C) amino-terminal and carboxyl-terminal residues that can donate or accept protons D) peptide bonds that readily ionize, consuming H' and OH ions E) amino acid residues with different pK_a values

Explanation / Answer

4. D)glycogen phosphorylase: Epinephrine and glucagon activates glycogen phosphorylase and inhibits glycogen synthase. They stimulates gluconeogenesis. There is activation of protein kinase A on release of these two hormones. It phosphorylates phosphorylase kinase which activates glycogen phosphorylase.

5. B) Cyanide inhibits respiratory chain by blocking cytochrome oxidase, Oligomycin inhibits ATP synthesis by inhibiting ATP synthase and other mechanism, DNP inhibits ATP synthesis by inhibiting oxidative phosphorylation.

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