Previously it was considered that after complete oxidation, NADH (Nictotinamide adenine dinucleotide) + H+ would liberate 3 ATP while FADH2 (Flavin adenine dinucleotide) would liberate 2 ATP.

However, according to recent concepts, complete oxidation of NADH + H+ will produce 2.5 ATP whereas complete oxidation of FADH2 will produce 1.5 ATP.