How many ATP molecules are produced from fermentation?

In the process of fermentation, a total of 2 ATP molecules are produced per glucose molecule. Fermentation is an anaerobic process, meaning it occurs in the absence of oxygen and allows cells to generate energy through the partial breakdown of glucose.

During glycolysis, which is the first step in both aerobic and anaerobic respiration, one glucose molecule is converted into two molecules of pyruvate, generating 2 NADH and a net gain of 2 ATP. Following glycolysis, in the absence of oxygen, fermentation pathways (like alcoholic fermentation or lactic acid fermentation) proceed to regenerate NAD+ so that glycolysis can continue, but they do not produce additional ATP.

Thus, the energy yield from fermentation results strictly from glycoylsis, culminating in the net gain of 2 ATP, which is characteristic of this metabolic pathway. This understanding is crucial for distinguishing fermentation from aerobic respiration, which yields significantly more ATP due to the complete oxidation of glucose.