How many ATP are generated during glycolysis?

During glycolysis, a total of 4 ATP molecules are produced. However, it is important to note that the process also consumes 2 ATP during the initial energy investment phase. As a result, the net gain of ATP from glycolysis is 2 ATP.

Glycolysis occurs in the cytoplasm and involves the breakdown of one molecule of glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon compound). The process encompasses ten enzymatic steps. In the energy payoff phase of glycolysis, two molecules of NADH and four ATP molecules are generated. After accounting for the 2 ATP molecules utilized at the beginning of glycolysis, the overall net gain stands at 2 ATP. This net yield emphasizes the efficiency of glycolysis in terms of ATP production relative to its initial investment.

The reason why understanding this process is crucial is that glycolysis is the first step in cellular respiration, and it sets the stage for subsequent metabolic pathways like the Krebs cycle and oxidative phosphorylation, which further contribute to ATP production in the presence of oxygen.