In glycolysis, only one oxidative reaction occurs in which the hydrogen liberated is accepted by $\mathrm{N}\mathrm{A}\mathrm{D}+$ forming $\mathrm{N}\mathrm{A}\mathrm{D}\mathrm{H}+\mathrm{H}+$. In this glyceraldehyde 3-phosphate is hydrogen donor and is oxidized to form 1,3 diphosphoglyceric acid.