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Metabolic
Many prokaryotes, yeasts, muscle cells
Fermentation (Anaerobic)
Regeneration of NAD⁺ from NADH under anaerobic conditions.
Overview
Fermentation allows glycolysis to continue in the absence of oxygen by regenerating NAD⁺. In lactic acid fermentation (muscle, Lactobacillus), pyruvate is reduced to lactate by lactate dehydrogenase. In alcoholic fermentation (yeast), pyruvate is decarboxylated to acetaldehyde, then reduced to ethanol. Both processes yield only 2 ATP per glucose (from glycolysis).
Cellular Location
Cytoplasm
Clinical Significance
Enables ATP production without oxygen; basis of brewing, baking, and dairy industries; lactic acid buildup causes muscle fatigue.