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[Biochemistry](https://durgical.com/en/biochemistry/) · Molecule

# NAD⁺ (nicotinamide adenine dinucleotide)

NAD⁺ picks up electrons in glycolysis and the Krebs cycle and carries them to the mitochondria as NADH. It is made from niacin.

Updated 2026-10-31

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## Key facts

- It accepts a hydride ion (H⁻) on its nicotinamide ring and becomes NADH.
- It is made from niacin (vitamin B3) or from tryptophan (about 60 mg of tryptophan per 1 mg of niacin).
- Cytosolic NADH enters the mitochondria through shuttles: malate–aspartate or glycerol-3-phosphate.
- NADH absorbs light at 340 nm and NAD⁺ does not: the basis of many lab enzyme assays.

**Formula**
C₂₁H₂₈N₇O₁₄P₂⁺

**PubChem**
[CID 5892](https://pubchem.ncbi.nlm.nih.gov/compound/5892)

## Structure

- Two nucleotides joined through their phosphates: one with nicotinamide (the working part), one with adenine.

## Clinical notes

- Niacin lack causes pellagra: dermatitis, diarrhea, dementia and, untreated, death.
- Hartnup disease and carcinoid syndrome can cause pellagra because they steal tryptophan.

## Pathways

- [Glycolysis](https://durgical.com/en/biochemistry/pathways/glycolysis/)
- [Krebs cycle (citric acid cycle)](https://durgical.com/en/biochemistry/pathways/krebs-cycle/)

## Related conditions

- [Lactic acidosis](https://durgical.com/en/conditions/lactic-acidosis/)

## Related

- [Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)](https://durgical.com/en/biochemistry/enzymes/glyceraldehyde-3-phosphate-dehydrogenase/)
- [Lactate](https://durgical.com/en/biochemistry/molecules/lactate/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which vitamin is NAD⁺ made from?

Niacin (vitamin B3); it can also be made from tryptophan.

## What are the three Ds of pellagra?

Dermatitis, diarrhea and dementia (the fourth is death).

## Which glycolysis step reduces NAD⁺ to NADH?

Step 6, glyceraldehyde-3-phosphate dehydrogenase.

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Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Nicotinamide adenine dinucleotide (CID 5892)](https://pubchem.ncbi.nlm.nih.gov/compound/5892) (PubChem, NCBI, 2026) · Public domain; [Pellagra: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000342.htm) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/molecules/nad/
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