What best explains why aerobic respiration is more energy efficient than anaerobic respiration?

Answer 1

Aerobic respiration produces 36 ATP from one glucose molecules. Anaerobic respiration produces only 2.

Two glucose molecules are produced during glycolysis. In addition to producing ATP from ADP, glycolysis also converts NAD+ to NADH. If no oxygen is available, more energy needs to be produced from glycolysis. However, for glycolysis to occur, NAD+ must be regenerated from NADH. Thus, in a process known as anaerobic fermentation, NAD+ is regenerated from NADH.

Fermentation doe snot fully oxydize glucose. After glycolysis, the glucose molecule has been converted into two molecules of pyruvate. Fermentation uses pyruvate to convert NAD+ back to NADH so it can be used for another round of glycolysis.

If oxygen is present, the two pyruvate molecules from glycolysis can be fully oxydized in a process known as aerobic respiration. This process consists of the citric acid cycle and the electron transport chain. The process is beyond the scope of this post, but aerobic respiration basically produces more NADH and FADH2 from pyruvate and uses the NADH/FADH2 molecules to oxydize O2 to H2O.

The Krebs cycle produces 2 ATP and the electron transport chain produces 32 ATP. Thus, aerobic respiration is a far more efficient means of energy production.