Final answer:
When one molecule of glucose is fermented, either to alcohol or lactic acid, a net of two ATP molecules are produced. This is a result of glycolysis where four ATPs are generated and two are used up. The net production remains two as no mitochondrial transport is involved in fermentation.
Step-by-step explanation:
The net ATPs synthesised during the fermentation of one molecule of glucose to alcohol or lactic acid are relatively low compared to aerobic respiration. During glycolysis, four ATP molecules are produced, but two are consumed, resulting in a net gain of two ATP molecules. In the case of alcohol fermentation, the glycolytic conversion of one molecule of glucose results in 2 ATP and two molecules of ethyl alcohol. Similarly, anaerobic conversion of pyruvate to lactate during lactic acid fermentation also yields 2 ATP per molecule of glucose.
However, these ATP molecules are not used for the transport of NADH produced during glycolysis, as this transport occurs in the mitochondria, which is not involved in fermentation. Hence, the net production of ATP during fermentation remains two. This contrasts sharply with the energy produced from aerobic respiration, which can yield up to 36-38 ATP molecules from the complete oxidation of a single glucose molecule.