Which steps in glycolysis are primarily responsible for ATP production?

In glycolysis, the steps primarily responsible for ATP production are those that involve substrate-level phosphorylation, which occurs at specific points during the pathway. Steps 7 and 10 are crucial in this context.

Step 7 involves the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, catalyzed by the enzyme phosphoglycerate kinase. In this reaction, an inorganic phosphate (Pi) is used to add a phosphate group to ADP, resulting in the formation of ATP. This is a clear example of substrate-level phosphorylation, where ATP is generated directly from a substrate.

Step 10 is another critical step in glycolysis, where phosphoenolpyruvate (PEP) is converted to pyruvate, catalyzed by pyruvate kinase. Similar to step 7, this step also results in the production of ATP through substrate-level phosphorylation. The energy released from the high-energy bond in the PEP molecule is used to convert ADP into ATP.

These two steps are the only points in glycolysis where ATP is produced directly through substrate-level phosphorylation, distinguishing them as the primary contributors to ATP production within the glycolytic pathway.