<P> Fates of pyruvate under anaerobic conditions: </P> <Ol> <Li> Pyruvate is the terminal electron acceptor in lactic acid fermentation When sufficient oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH produced in glycolysis, NAD+ is regenerated from NADH by reduction of pyruvate to lactate . Pyruvate is converted to lactate by the enzyme lactate dehydrogenase . The standard free energy change of the reaction is - 25.1 kJ / mol . </Li> <Li> Ethanol fermentation Yeast and other anaerobic microorganisms convert glucose to ethanol and CO2 rather than pyruvate . Pyruvate is first converted to acetaldehyde by enzyme pyruvate decarboxylase in the presence of Thiamine pyrophosphate and Mg++ . Carbon - dioxide is released during this reaction . Acetaldehyde is then converted to ethanol by the enzyme alcohol dehydrogenase . NADH is oxidized to NAD+ during this reaction . </Li> </Ol> <Li> Pyruvate is the terminal electron acceptor in lactic acid fermentation When sufficient oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH produced in glycolysis, NAD+ is regenerated from NADH by reduction of pyruvate to lactate . Pyruvate is converted to lactate by the enzyme lactate dehydrogenase . The standard free energy change of the reaction is - 25.1 kJ / mol . </Li> <Li> Ethanol fermentation Yeast and other anaerobic microorganisms convert glucose to ethanol and CO2 rather than pyruvate . Pyruvate is first converted to acetaldehyde by enzyme pyruvate decarboxylase in the presence of Thiamine pyrophosphate and Mg++ . Carbon - dioxide is released during this reaction . Acetaldehyde is then converted to ethanol by the enzyme alcohol dehydrogenase . NADH is oxidized to NAD+ during this reaction . </Li>

The conversion of pyruvate to lactate during exercise requires
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