In which of the following reactions of glycolysis does oxidation take place?

Explanation

In glycolysis, most reactions involve phosphorylation, but only one includes oxidation. The conversion of glucose to glucose-6-phosphate by hexokinase and fructose-6-phosphate to fructose-1,6-bisphosphate by phosphofructokinase uses ATP for phosphorylation without oxidation. The step where glyceraldehyde-3-phosphate is converted to 1,3-bisphosphoglycerate by glyceraldehyde-3-phosphate dehydrogenase is the only oxidation step, where NAD⁺ is reduced to NADH. The final conversion of phosphoenolpyruvate to pyruvate by pyruvate kinase produces ATP through substrate-level phosphorylation but no oxidation. Thus, oxidation occurs only in the glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate step.