Biochemistry Questions / Explain the significance of fermentation in the absence of aerobic and anaerobic respiration. How does the use of endogenous organic molecules impact ATP synthesis?

Fermentation is an anaerobic process, preventing the use of oxygen as the terminal electron acceptor. In place of oxygen, alternative electron acceptors are used.

Alternative electron acceptors are organic molecules found within, or synthesised by, the cell. Normally, pyruvate is used as the alternative electron acceptor.

The ability to maintain the redox balance in the cell is more difficult in anaerobic conditions. NADH is re-oxidised back to NAD+, producing fermentation products in the process (lactic acid, alcohols, …).

Depending on the specific fermentation process used, 1-3 moles ATP can be obtained. This is far lower than the quantity of ATP synthesised during aerobic respiration.