Substrate-level phosphorylations occur when a "high-energy" phosphate containing molecule transfers phosphate to ADP in a chemical reaction to form ATP. Two examples of this type of reaction occur in glycolysis:

1. The reaction catalyzed by the enzyme phosphoglycerate kinase. In this reaction, a high energy phosphate from 1,3 bisphosphoglycerate is transferred to ADP to form ATP and 3-phosphoglycerate.

2. The reaction catalyzed by the enzyme pyruvate kinase. Here, a high energy phosphate is transferred from PEP to ADP to form ATP and pyruvate.