Energy-yielding phase
The energy yielding phase of glycolysis, also called the "pay off" phase, results in the production of 4 ATPs (2 per glucose molecule) and the reduction of NAD+ to NADH. First, the phosphorylation of Glycerealdehyde 3-Phosphate by the Triose phosphate dehydrogenase enzyme produces the molecule 1,3-Biphosphoglycerate (BPG). Next, the enzyme Phosphoglycerate kinase reacts with the BPG molecule to produce ATP and 3-Phosphoglycerate (3-PG). This production of 2 ATPs balances the investment of 2 ATPs during the energy investment phase. A phosphate group of 3-PG is then transferred from the third carbon to the second carbon by phosphoglyceromutase, producing 2-Phosphoglycerate. The enzyme Enolase then converts the 2-Phosphoglycerate into phosphoenolpyruvate (PEP). This step releases potassium, magnesium, and H2O. Finally, PEP is transferred to ADP by the enzyme pyruvate kinase, producing another two ATP molecules and pyruvate. Overall, the energy yielding phase uses glucose, NAD+, 2 ADP, and 2 Pi to produce 2 pyruvate, 2 NADH, 2H, and 2 net ATP.