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Unformatted text preview: February 21, 2007 ATP synthesis is reversible ATP to ADP +P i + free energy ATP synthase can also work as an ATPase Why is synthesis preferred? ATP leaves the mitochondrion as soon as it is made The electron transport chain maintains the H + gradient Uncoupling proton diffusion and ATP synthesis Proton diffusion and ATP synthesis are tightly coupled Protons must pass only through the ATP synthase channel Insert another proton channel and these processes are uncoupled Energy of proton gradient is released as heat Some organisms do this deliberately to generate extra heat Hibernating animals, human infants Fermentation The breakdown of pyruvate from glycolysis in the absence of O 2 Releases much less energy than cellular respiration Only 2 ATP molecules for every glucose Why do cells need fermentation? Times of low O 2 supply No NAD + and FAD are regenerated Used by some cells to produce small amounts of ATP when O 2 supply is low Uses NADH + H + to reduce pyruvate regenerating NAD+...
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- Spring '08
- Electron Transport Chain