Difference Between NAD and FAD

It is found in all the cells which are living. As the name dinucleotide suggests, it has two nucleotides that are joined together by phosphate groups. NAD can be found in two forms, i.e., oxidized and reduced form or state.

FAD is Flavin adenine dinucleotide is a cofactor which is the type of coenzyme, and it is involved in various enzymatic reactions that are necessary for metabolism.

Comparison Table Between NAD and FAD

Parameters of Comparison NADFAD
Full formNAD  is Nicotinamide adenine dinucleotide.FAD is Flavin adenine dinucleotide.
DefinitionNAD is a coenzyme that can be found in living cells.FAD is a redox cofactor involved in many metabolic and complex reactions.
ProductionIt is produced during glycolysis and the Krebs cycle.It is only produced during the Krebs cycle.
HydrogenIt accepts only one9 hydrogen atom.It can accept two hydrogen atoms.
Electron TransferIt transfers its electron to Cytochrome Complex 1 and gives 3 ATP.It transfers its electron to Cytochrome Complex 2 and gives 2 ATP.

What is NAD?

 Nicotinamide adenine dinucleotide is also known by the name NAD consists of two nucleotides that are joined together by a phosphate group.

Apart from electron transfer, it also helps in the cellular process, such as acting as a catalyst or reagent of enzymes or adding and subtracting chemical groups from the protein itself. NAD and its enzymes are so important that it becomes very vital in drug discovery.

It has a molar mass of 663.43g/molecule. Its melting point is 60 °C (320 °F; 433 K). It looks like a white powder whether it is in any state and is hygroscopic and water-soluble(highly) in nature.

What is FAD?

Flavin adenine dinucleotide is also known by the name FAD, is very vital in the field of biochemistry. It is a redox-active coenzyme that is associated with different types of protein. It has four states in which it can exist: quinone, semiquinone,flavin-N(5)-oxide, and hydroquinone.

Like NAD, FAD also has two parts which are adenine nucleotide, and the flavin mononucleotide (FMN) bonded together by phosphate groups. FAD can be reduced to form FADH2 by accepting two hydrogens and two electrons.

In different states, FAD has different colors. Like in a super oxidized state, it turns yellow-orange. In the fully oxidized state, it is yellow. In the half-reduced form, it is either red or blue-like pH, and if reduced fully, it becomes colorless.

Main Differences Between NAD and FAD

  1. NAD accepts only one hydrogen atom. FAD can accept two hydrogen atoms.
  2. NAD transfers its electron to Cytochrome Complex 1 and gives 3 ATP for each NADH produced. FAD transfers its electron to Cytochrome Complex 2 and gives 2 ATP for each FDH2 produced.


Both NAD and FAD are actively involved in the process of cellular respiration. Both are derived from proteins and accept high-energy electrons and carry them to the electron transport chain.

Both are coenzymes. NAD is very important for carrying and delivering hydrogen and electrons in the biochemical process, whereas FAD uses electrons and hydrogen to make ATP.


  1. https://pubs.acs.org/doi/abs/10.1021/bi002061f
  2. https://academic.oup.com/nar/article-abstract/31/3/e8/1130007

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