What is the net ATP gain from glycolysis per glucose molecule?

The net ATP gain from glycolysis per glucose molecule is indeed 2 ATP. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate through a series of enzymatic reactions.

In the initial stages of glycolysis, energy is invested in the form of ATP to facilitate the conversion of glucose into more reactive intermediates. Specifically, two ATP molecules are used in the energy investment phase. However, in the subsequent steps of glycolysis, four ATP molecules are produced through substrate-level phosphorylation. This results in a gross production of four ATPs.

To determine the net gain, you subtract the two ATPs that were used at the beginning from the four ATPs produced, resulting in a net gain of 2 ATP per glucose molecule. This is a crucial aspect of cellular respiration and metabolic processes, as it represents a small but important return on energy investment for the cell.