What is the net yield of ATP in anaerobic metabolism from one glucose molecule?

In anaerobic metabolism, glucose is broken down through a process called glycolysis, which occurs in the cytoplasm of the cell. The key outcome of glycolysis is the conversion of one molecule of glucose into two molecules of pyruvate, generating a small amount of energy in the form of ATP.

During glycolysis, a net yield of 2 ATP molecules is produced from each glucose molecule. Although a total of 4 ATP molecules are generated, 2 ATP molecules are used in the initial steps of glycolysis, resulting in a net gain of 2 ATP. This process does not require oxygen, and it is vital for cells that are in conditions where oxygen concentration is low or absent.

Following glycolysis, in the absence of oxygen, cells can further metabolize the pyruvate into lactic acid (in animals) or ethanol and carbon dioxide (in yeast), but this conversion does not yield any additional ATP beyond the 2 earned during glycolysis. Hence, the net yield of ATP from one glucose molecule during anaerobic metabolism remains at 2 ATP.