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

# Arachidonic acid

Arachidonic acid is a 20-carbon omega-6 fatty acid stored in cell membranes. Released on demand, it is the source of all eicosanoids.

Updated 2026-11-01

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## Key facts

- Stored at position sn-2 of membrane phospholipids and freed by phospholipase A₂.
- COX turns it into prostaglandins and thromboxane; 5-lipoxygenase turns it into leukotrienes.
- Humans make it from linoleic acid, an essential fatty acid of the diet.

**Also called**
20:4 ω-6

**Formula**
C₂₀H₃₂O₂

**PubChem**
[CID 444899](https://pubchem.ncbi.nlm.nih.gov/compound/444899)

## Structure

- A 20-carbon chain with four cis double bonds (5, 8, 11, 14) and a carboxyl end.

## Clinical notes

- NSAIDs and glucocorticoids act by limiting what is made from it.
- Omega-3 fatty acids compete with it and lead to less inflammatory eicosanoids.
- Essential fatty acid deficiency (scaly skin, poor growth) appears when linoleic acid is lacking.

## Pathways

- [Prostaglandin and thromboxane synthesis](https://durgical.com/en/biochemistry/pathways/prostaglandin-and-thromboxane-synthesis/)

## Related conditions

- [Asthma](https://durgical.com/en/conditions/asthma/)

## Related

- [Phosphatidylcholine (lecithin)](https://durgical.com/en/biochemistry/molecules/phosphatidylcholine/)
- [Prostaglandin H₂ (PGH₂)](https://durgical.com/en/biochemistry/molecules/prostaglandin-h/)
- [Thromboxane A₂ (TXA₂)](https://durgical.com/en/biochemistry/molecules/thromboxane-a/)
- [Cyclooxygenase (COX-1 and COX-2)](https://durgical.com/en/biochemistry/enzymes/cyclooxygenase/)
- [Eicosanoids: prostaglandins, thromboxanes and leukotrienes](https://durgical.com/en/biochemistry/topics/eicosanoids-prostaglandins-thromboxanes-and-leukotrienes/)
- [Phospholipids](https://durgical.com/en/biochemistry/topics/phospholipids/)
- [Lipid chemistry](https://durgical.com/en/biochemistry/topics/lipid-chemistry/)

## Test yourself

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

## Which enzyme releases arachidonic acid from the membrane?

Phospholipase A₂, which cuts at position sn-2.

## From which dietary fatty acid is arachidonic acid made?

Linoleic acid, an essential omega-6 fatty acid.

## Which two enzyme families turn arachidonic acid into signals?

Cyclooxygenases (prostaglandins, thromboxane) and lipoxygenases (leukotrienes).

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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: [Arachidonic Acid (CID 444899)](https://pubchem.ncbi.nlm.nih.gov/compound/444899) (PubChem, NCBI, 2026) · Public domain; [Cytosolic phospholipase A2 (PLA2G4A) - Homo sapiens](https://www.uniprot.org/uniprotkb/P47712/entry) (UniProt, 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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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/molecules/arachidonic-acid/