Energy gain in one complete cycle of aerobic respiration is :

In aerobic respiration complete oxidation of one glucose molecule produces 38 ATP molecules. But the number of ATP molecules so produced may vary depending upon the mode of entry of NADH₂ in the mitochondria. If the electrons of NADH₂ are accepted by malate then each molecule of NADH₂ yields 3 ATP molecules and the total would be 38 ATP molecules. But if the electrons of NADH₂ are accepted by FAD it yields only 2 ATP molecules making the total of 36 ATP molecules. This type of shuttle occurs in most of the eukaryotic cells.