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

# Squalene

Squalene is a linear 30-carbon hydrocarbon, with no oxygen, that folds up to form the first sterol.

Updated 2026-11-01

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## Key facts

- It forms when two farnesyl pyrophosphates (C15) are joined tail-to-tail with NADPH (squalene synthase).
- It is the first intermediate used only for sterols: earlier ones also feed other isoprenoids.
- Squalene epoxidase oxidises it to 2,3-oxidosqualene, which lanosterol synthase cyclises.

**Formula**
C₃₀H₅₀

**PubChem**
[CID 638072](https://pubchem.ncbi.nlm.nih.gov/compound/638072)

## Structure

- Six isoprene units with six trans double bonds; very hydrophobic.
- It is abundant in shark-liver oil (hence the name, from Squalus) and in human sebum.

## Clinical notes

- Fungi treated with terbinafine accumulate squalene, which is toxic to them.
- Squalene emulsions are used as an adjuvant in some vaccines.

## Pathways

- [Cholesterol synthesis (mevalonate pathway)](https://durgical.com/en/biochemistry/pathways/cholesterol-synthesis/)

## Related

- [Isopentenyl pyrophosphate (IPP)](https://durgical.com/en/biochemistry/molecules/isopentenyl-pyrophosphate/)
- [Squalene epoxidase](https://durgical.com/en/biochemistry/enzymes/squalene-epoxidase/)
- [Lanosterol](https://durgical.com/en/biochemistry/molecules/lanosterol/)

## Test yourself

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

## How is squalene formed?

Squalene synthase joins two farnesyl pyrophosphates tail-to-tail using NADPH.

## Which enzyme acts on squalene, and which drug blocks it in fungi?

Squalene epoxidase; terbinafine inhibits it in fungi.

## Why is squalene called the first sterol-committed intermediate?

Because earlier compounds also make other isoprenoids, while squalene only goes on to sterols.

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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: [Squalene (CID 638072)](https://pubchem.ncbi.nlm.nih.gov/compound/638072) (PubChem, NCBI, 2026) · Public domain; [Cholesterol biosynthesis (R-HSA-191273)](https://reactome.org/PathwayBrowser/#/R-HSA-191273) (Reactome, 2026).

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Representative model, for educational purposes only.

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