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

# Ubiquinone (coenzyme Q₁₀)

Ubiquinone is a fatty molecule that moves within the mitochondrial membrane and carries electrons from complexes I and II to complex III.

Updated 2026-11-01

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## Key facts

- It receives electrons from complex I, complex II, glycerol-3-phosphate dehydrogenase and fatty acid oxidation (ETF).
- It accepts 2 electrons and 2 protons: ubiquinone (Q) → semiquinone (radical) → ubiquinol (QH₂).
- It is not a vitamin: the body makes it; its isoprene tail comes from the mevalonate pathway, the same as cholesterol.
- In its reduced form it is also a membrane antioxidant.

**Also called**
Coenzyme Q, CoQ10

**Formula**
C₅₉H₉₀O₄

**PubChem**
[CID 5281915](https://pubchem.ncbi.nlm.nih.gov/compound/5281915)

## Structure

- A benzoquinone ring (the part that takes electrons) with a tail of 10 isoprene units that anchors it in the bilayer.

## Clinical notes

- Statins inhibit HMG-CoA reductase and lower plasma ubiquinone; its role in muscle pain is still debated.
- Primary coenzyme Q₁₀ deficiency is a rare mitochondrial disease (encephalopathy, nephropathy, ataxia) that can improve with supplements.
- The semiquinone can give one electron to O₂ and form superoxide.

## Pathways

- [Electron transport chain and oxidative phosphorylation](https://durgical.com/en/biochemistry/pathways/electron-transport-chain-and-oxidative-phosphorylation/)
- [Pyrimidine synthesis](https://durgical.com/en/biochemistry/pathways/pyrimidine-synthesis/)

## Related

- [Complex I (NADH dehydrogenase)](https://durgical.com/en/biochemistry/enzymes/complex-i/)
- [Complex III (cytochrome bc₁)](https://durgical.com/en/biochemistry/enzymes/complex-iii/)
- [Succinate dehydrogenase (complex II)](https://durgical.com/en/biochemistry/enzymes/succinate-dehydrogenase/)
- [Cytochrome c](https://durgical.com/en/biochemistry/enzymes/cytochrome-c/)
- [HMG-CoA reductase](https://durgical.com/en/biochemistry/enzymes/hmg-coa-reductase/)
- [Mitochondrial NADH shuttles](https://durgical.com/en/biochemistry/topics/mitochondrial-nadh-shuttles/)

## Test yourself

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

## Which complexes give electrons to ubiquinone?

Complex I (from NADH) and complex II (from succinate's FADH₂), plus other membrane dehydrogenases.

## Which metabolic pathway supplies ubiquinone's tail?

The mevalonate pathway, the same as cholesterol.

## Why do statins lower coenzyme Q₁₀?

They inhibit HMG-CoA reductase, which makes the mevalonate its isoprene tail is built from.

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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: [Coenzyme Q10 (CID 5281915)](https://pubchem.ncbi.nlm.nih.gov/compound/5281915) (PubChem, NCBI, 2026) · Public domain; [Ubiquinol biosynthesis](https://reactome.org/PathwayBrowser/#/R-HSA-2142789) (Reactome, 2026); [Primary coenzyme Q10 deficiency: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/primary-coenzyme-q10-deficiency/) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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