Key Difference – NADH vs FADH2 A coenzyme is an organic non-protein molecule which is relatively small in size and has the ability to carry chemical groups between enzymes and act as an electron carrier. NADH (Nicotinamide Adenine Dinucleotide) and FADH2 (Flavin Adenine Dinucleotide) are two main coenzymes utilized in almost all biochemical pathways. […]