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

# Ethanol

The alcohol in drinks: a small molecule that crosses every membrane and that the liver oxidises to acetaldehyde and acetate.

Updated 2026-11-01

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## Key facts

- CH₃–CH₂–OH: soluble in water and slightly in fat, it spreads through total body water.
- It supplies about 7 kcal per gram with no vitamins or protein (empty calories).
- Over 90 % is oxidised in the liver; a small part leaves in urine and breath (the basis of the breathalyser).
- It depresses the nervous system: it enhances GABA-A receptors and inhibits NMDA receptors.

**Also called**
Ethyl alcohol

**Formula**
C₂H₆O

**PubChem**
[CID 702](https://pubchem.ncbi.nlm.nih.gov/compound/702)

## Structure

- Two carbons with a hydroxyl group (–OH) at one end.

## Clinical notes

- Women reach higher levels with the same amount: less body water and less gastric ADH.
- Chronic use causes thiamine (Wernicke), folate and magnesium deficiency.
- It raises the osmolal gap; in methanol and ethylene glycol poisoning it is used as a competitive inhibitor of alcohol dehydrogenase when fomepizole is unavailable.

## Pathways

- [Ethanol metabolism](https://durgical.com/en/biochemistry/pathways/ethanol-metabolism/)

## Related conditions

- [Alcoholic liver disease (biochemistry)](https://durgical.com/en/conditions/alcoholic-liver-disease/)
- [Wernicke encephalopathy (thiamine deficiency)](https://durgical.com/en/conditions/wernicke-encephalopathy/)
- [Methanol poisoning](https://durgical.com/en/conditions/methanol-poisoning/)

## Related

- [Acetaldehyde](https://durgical.com/en/biochemistry/molecules/acetaldehyde/)
- [Alcohol dehydrogenase (ADH)](https://durgical.com/en/biochemistry/enzymes/alcohol-dehydrogenase/)
- [Cytochrome P450 2E1 (CYP2E1, MEOS)](https://durgical.com/en/biochemistry/enzymes/cytochrome-p450-2e1/)
- [Aldehyde dehydrogenase 2 (ALDH2)](https://durgical.com/en/biochemistry/enzymes/aldehyde-dehydrogenase-2/)
- [Thiamine (vitamin B1)](https://durgical.com/en/biochemistry/molecules/thiamine/)

## Test yourself

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

## Why does ethanol provide «empty calories»?

It gives energy (about 7 kcal/g) when oxidised but brings no vitamins, minerals or protein.

## Which vitamin deficiency is typical of chronic ethanol use and what does it cause?

Thiamine (B1) deficiency: Wernicke encephalopathy.

## Why can ethanol work as an antidote in methanol poisoning?

It competes for alcohol dehydrogenase and slows the formation of formic acid.

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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: [Ethanol (CID 702)](https://pubchem.ncbi.nlm.nih.gov/compound/702) (PubChem, NCBI, 2026); [Ethanol oxidation](https://reactome.org/PathwayBrowser/#/R-HSA-71384) (Reactome, 2026); [Alcohol](https://www.who.int/news-room/fact-sheets/detail/alcohol) (World Health Organization, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/molecules/ethanol/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/molecules/ethanol/