Fermentation in cells occurs in the cytoplasm , not in the mitochondria.

Short answer

  • In both prokaryotic and eukaryotic cells, fermentation pathways (like lactic acid and alcoholic fermentation) take place in the cytoplasm, where pyruvate is converted into products such as lactate or ethanol while regenerating NAD⁺.
  • In human bodies, this is especially important in muscle cells during intense exercise when oxygen is low, so those muscle cells ferment in their cytoplasm and produce lactic acid.

So whenever the question is “where does fermentation occur?” in a cellular respiration context, the precise location to remember is: the cytoplasm of the cell.

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