When an organism such as a yeast lives by fermentation, it converts the pyruvate from glycolysis into a different compound, such as alcohol. Why doesn't it secrete the pyruvate directly?

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Quizplus · Accepted Answer

The conversion of pyruvate into a different compound, such as alcohol in yeast, is necessary to regenerate NAD+, which is needed for glycolysis to continue. Glycolysis requires a supply of NAD+ to oxidize glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate, and the conversion of pyruvate into alcohol (or lactate in other organisms) regenerates NAD+ from NADH, allowing glycolysis to proceed and produce ATP anaerobically.

When an Organism Such as a Yeast Lives by Fermentation