NAD vs FAD

FAD is flavin adenine dinucleotide, and NAD is nicotinamide adenine dinucleotide. Both the FAD and NAD are electron carriers which have many roles to perform.

Nicotinamide adenine dinucleotide is a coenzyme that is found in all living beings. The nucleotides in NAD are joined together by phosphate groups. Flavin adenine dinucleotide is considered a redox cofactor that is related to many metabolic reactions. FAD also exists in two redox states.

One of the main differences that can be seen between FAD, flavin adenine dinucleotide, and NAD, nicotinamide adenine dinucleotide, is in the difference of accepting hydrogen atoms. FAD can accommodate two hydrogens whereas NAD accepts just one hydrogen. In NAD, a single hydrogen and an electron pair is transferred, and the second hydrogen is freed into the medium. This is why the reduced flavin adenine dinucleotide form has been written as FADH2, and the reduced nicotinamide adenine dinucleotide is NADH + H+.

Nicotinamide adenine dinucleotide gets reduced to NADH in Krebs and glycolysis. It feeds into the electron transport chain at Complex 1 and also gives 3 ATP for every NADH. Flavin adenine dinucleotide is normally reduced to FADH2 in the Krebs cycle. It feeds into the electron transport chain at Complex 11 and also gives 2 ATP for every FADH2.

During electron transfer, the flavin adenine dinucleotide and nicotinamide adenine dinucleotide reduce cytochromes differently. While NADH+H+ reduces Cytochrome I, FADH2 is known to reduce Cytochrome II.

Summary:

1.FAD is flavin adenine dinucleotide, and NAD is nicotinamide adenine dinucleotide.
2.Nicotinamide adenine dinucleotide is a coenzyme that is found in all living beings. Flavin adenine dinucleotide is considered a redox cofactor that is related to many metabolic reactions.
3.Flavin adenine dinucleotide can accommodate two hydrogens whereas nicotinamide adenine dinucleotide accepts just one hydrogen.
4.Nicotinamide adenine dinucleotide gets reduced to NADH in Krebs and glycolysis. Flavin adenine dinucleotide is normally reduced to FADH2 in the Krebs cycle.
5.While NADH+H+ reduces Cytochrome I, FADH2 is known to reduce Cytochrome II.
6.Reduced flavin adenine dinucleotide form has been written as FADH2, and the reduced nicotinamide adenine dinucleotide is NADH + H+.
7.Nicotinamide adenine dinucleotide feeds into the electron transport chain at Complex 1 and also gives 3 ATP for every NADH. Flavin adenine dinucleotide feeds into the electron transport chain at Complex 11 and also gives 2 ATP for every FADH2.

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