Anaerobic Respiration (Fermentation)

1. Anaerobic respiration (fermentation):

    - respiration takes place in the absence of O2
    - occurs only in the cytoplasm.

    - produces: pyruvate, 2 NADH + 2 mol ATP 
    - pyruvate + NADH accumulate in cytoplasm

2. - pyruvate + NADH accumulate in cytoplasm
       --> causes tissues to run out of H acceptor (NAD+) - limited supply.

       --> glycolysis may not occur.

       --> need for an alternative H acceptor.

       --> pyruvate or acetaldehyde becomes the H acceptor.

       --> pyruvate can undergo both aerobic and anaerobic respiration.

3. In plants:

    - pyruvate undergoes alcohol fermentation --> produce ethanol,
    - occurs in roots of the plants (water logged conditions).

4. In animals:

    - pyruvate undergoes lactic acid fermentation --> produce lactic acid
    - occurs in the muscles during vigorous activity + strenuous exercise.

7. Fermentation products are used commercially.

    - Wine, methanol and formic acid are formed by alcohol fermentation.

    - Yogurt, cheese and soy sauce are formed by lactic acid fermentation.