How many ATP molecules are produced from one molecule of glucose during glycolysis?

Glycolysis is the initial step of cellular respiration that occurs in the cytoplasm of the cell. During this process, one molecule of glucose, which is a six-carbon sugar, is broken down into two molecules of pyruvate. Throughout the glycolytic pathway, there are two main phases: the energy investment phase and the energy payoff phase.

In the energy investment phase, two ATP molecules are consumed to help initiate the breakdown of glucose. However, during the energy payoff phase, a total of four ATP molecules are generated through substrate-level phosphorylation as the pyruvate molecules are formed. Therefore, when considering the net gain of ATP from glycolysis, two ATP molecules are produced after accounting for the two that were utilized in the investment phase.

This leads to the conclusion that for each molecule of glucose that undergoes glycolysis, a net yield of two ATP molecules can be obtained, making this understanding crucial for grasping the overall energy yield from glucose during the first stage of cellular respiration.