Solns prob set #2

Solns prob set #2 - BIPN 108, Physiology of Exercise,...

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BIPN 108, Physiology of Exercise, Solutions to problem set #2 Page 1 1. a. The three phases of energy metabolism are: (1) glycolysis takes place in the cytoplasm and produces either 4 or 6 ATPs per glucose molecule, depending on whether the O 2 supply is adequate to allow the electron transport system to function (2) the citric acid cycle takes place in mitochondria and produces 30 ATPs per glucose molecule if the O 2 supply is adequate to allow the electron transport system to function (it contributes only 2 ATPs if the electron transport system cannot function, and it wouldn’t do that for very long because accumulation of NADH would halt the reactions) (3) the electron transport system is located in the mitochondria and produces 32 ATPs per glucose molecules, but only if sufficient O 2 is available. b. A wide variety of substrate molecules are converted to pyruvate or to acetyl co-A, and these two molecules then proceed through the citric acid cycle. c. In anaerobic conditions, NADH is produced during glycolysis. Because insufficient O 2 is available to allow the electron transport chain to work, the NADH could build up and force glycolysis to stop. Instead, NADH reduces pyruvate to lactate, which restores the supply of NAD + and allows glycolytic production of ATP to continue. (Accumulation of lactate in working muscle fibers would also slow down the pyruvate -> lactate conversion, but lactate leaves the muscle fibers--driven by its concentration gradient--and enters the bloodstream, which carries it away, so it is not allowed to accumulate.) In aerobic conditions, NADH is produced at several steps in glycolysis and in the citric acid cycle. The NADH molecules transfer electrons to the electron transport system, becoming oxidized in the process, and ATP is synthesized as the electrons travel along the
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Solns prob set #2 - BIPN 108, Physiology of Exercise,...

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