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FERMENTATION
- define: a metabolic pathway that regenerates NAD+ from stockpiles of NADH, allows glycolysis to continue producing ATP in absence of oxygen
- process stops before pyruvate processing
- in most organisms cellular respiration cannot occur without oxygen
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when does it occur?
- when pyruvate or a molecule derived from pyruvate accepts e- from NADH
- the transfer of e- oxidizes NADH to NAD+
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with NAD+
glycolysis can continue to produce ATP via substrate-level phosphorylation
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fermentation will end with:
- a net of 2 ATP
- per glucose molecule:
- fermentation --- 2 ATP
- cellular respiration --- 29 ATP
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different fermentation pathways
- lactic acid fermentation: occurs in most multi-cellular organisms
- alcohol fermentation: ethanol & NAD+ are produced, occurs in yeast
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lactic acid fermentation
- pyruvate produced by glycolysis accepts e- from NADH
- lactate and NAD+ are produced
- occurs in muscle cells
- *no oxygen present
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alcohol fermentation
- pyruvate is enzymatically converted to acetaldehyde & CO2
- acetaldehyde accepts e- from NADH
- ethanol & NAD+ are produced
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what happens during extreme exercise
- no O2 present:
- glucose --- pyruvate(oxidized) + NADH(reduced) ---lactate(reduced) + NAD+(oxidized)
- NAD+ is reused to make more glucose to start the process all over
- build up of lactic acid...side cramp! end with a lot of lactic acid in liver, its converted to glucose(in case lack of more O2)
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