How many ATP molecules are produced through anaerobic respiration?

Anaerobic respiration primarily occurs in the absence of oxygen and is less efficient at generating ATP compared to aerobic respiration. In anaerobic processes such as lactic acid fermentation (in animals) or alcoholic fermentation (in yeast), glucose is partially broken down to yield ATP.

During anaerobic respiration, glucose undergoes glycolysis, which produces 2 ATP molecules directly for each glucose molecule that is processed. After glycolysis, the pyruvate generated is further converted into lactic acid or ethanol and carbon dioxide, depending on the organism, but this conversion does not yield additional ATP. Therefore, the net production of ATP through anaerobic respiration is generally confirmed to be 2 ATP molecules per molecule of glucose.

This understanding of the ATP yield helps clarify why the other available choices represent incorrect values for ATP production in anaerobic respiration. The higher figures like 36-38 represent the ATP yield from aerobic respiration, where oxygen is present and the full oxidative phosphorylation pathway is utilized. The value of 4 does not correspond with typical anaerobic pathways, and the production of only 1 ATP is not accurate within the context of anaerobic respiration's glycolysis stage, which provides at least 2 ATP molecules.