Glycolysis requires NAD⁺ and both fermentation and aerobic respiration start with glycolysis.  In glycolysis, the NAD⁺ hydrogen carrier is reduced to NADH₂ and two molecules of ATP are produced. The only ATP that is generated in fermentation is produced at this point.  Fermentation  is needed to ensure that ATP continues to be produced in glycolysis. Thus, the pyruvate that is also generated in glycolysis   acts as the final acceptor of hydrogen from NADH₂, regenerating   NAD⁺.  What acts as the final hydrogen acceptor in aerobic respiration?? Hopefully, you are thinking oxygen!