What is the net gain of ATP molecules from one molecule of glucose during glycolysis?

During glycolysis, one molecule of glucose is metabolized through a series of enzymatic reactions that ultimately convert it into two molecules of pyruvate. This process occurs in the cytoplasm and involves several key steps.

In the energy investment phase of glycolysis, two ATP molecules are consumed to activate glucose and facilitate its breakdown. However, in the energy payoff phase, four ATP molecules are produced as the resulting three-carbon molecules undergo further transformations. Therefore, when considering both the ATP consumed and the ATP produced, the net gain is calculated as follows:

ATP produced (4) - ATP used (2) = 2 ATP.

This net gain of two ATP molecules is crucial because it represents the energy yield from the breakdown of glucose during the first stage of cellular respiration. It should be noted that glycolysis does not represent the total ATP yield from glucose since additional ATP can be generated through further processes such as the Krebs cycle and oxidative phosphorylation later in cellular respiration.