Which step in glycolysis generates the energy carrier molecule NADH?

In glycolysis, the generation of the energy carrier molecule NADH occurs specifically during Step 6. This step involves the enzyme glyceraldehyde-3-phosphate dehydrogenase, which catalyzes the oxidation and phosphorylation of glyceraldehyde-3-phosphate (G3P). During this process, G3P is converted to 1,3-bisphosphoglycerate, and in the reaction, NAD+ is reduced to NADH.

The conversion of NAD+ to NADH is a critical part of cellular metabolism because NADH serves as a key electron carrier. It stores energy that can later be used in the electron transport chain during cellular respiration, highlighting the importance of this step in both glycolysis and overall energy production in the cell. The production of NADH here is vital for both anaerobic and aerobic conditions, as it allows glycolysis to continue.

Steps 4, 5, and 8 do not involve the direct generation of NADH, focusing instead on the conversion of substrates that do not include redox reactions leading to NADH production.