2. Both cellular respiration and fermentation convert nutrients from sugar, amino acids and fatty acids to form ATP, but they differ in their processes and levels of energy that they release. 3. Cellular respiration produces 38 ATP, while fermentation produces only 2 ATP.
Fermentation and cellular respiration differ in one critical factor: oxygen. Cellular respiration uses oxygen in the chemical reaction that releases energy from food. Because fermentation doesn't use oxygen, the sugar molecule doesn't break down completely and so releases less energy.