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
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
Related
- Complex I (NADH dehydrogenase)
- Complex III (cytochrome bc₁)
- Succinate dehydrogenase (complex II)
- Cytochrome c
- HMG-CoA reductase
- 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.
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) (PubChem, NCBI, 2026) · Public domain; Ubiquinol biosynthesis (Reactome, 2026); Primary coenzyme Q10 deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
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