Biochemistry · Molecule
Cholesterol !
Cholesterol is a 27-carbon sterol that stiffens membranes and is the raw material for steroid hormones, bile acids and vitamin D.
Updated 2026-11-01
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Key facts
- Four fused rings, an OH on C3 and an 8-carbon side chain: amphipathic but almost insoluble in water.
- It travels in blood inside lipoproteins, about two-thirds as cholesteryl ester.
- The body makes it (mainly the liver) and gets it from animal foods; plants contain no cholesterol.
- It is not broken down to CO₂: it leaves the body as cholesterol in bile and as bile acids.
- Desirable total cholesterol in adults: below 200 mg/dL.
- Formula
- C₂₇H₄₆O
- PubChem
- CID 5997
Structure
- The C3 OH faces the water and the rest sinks between phospholipids: it stiffens fluid membranes and loosens rigid ones.
- Cholesteryl ester loses the free OH and is even more hydrophobic: it is stored in lipid droplets or the lipoprotein core.
Clinical notes
- High LDL deposits cholesterol in the artery wall and forms atheromatous plaques.
- Bile supersaturated with cholesterol forms gallstones.
- Tendon xanthomas or corneal arcus in a young person suggest familial hypercholesterolaemia.
Pathways
- Cholesterol synthesis (mevalonate pathway)
- Adrenal cortisol synthesis
- Classic bile acid synthesis pathway
Related conditions
Related
- Lanosterol
- HMG-CoA reductase
- LDL (low-density lipoprotein)
- HDL (high-density lipoprotein)
- Bile acid synthesis
- Steroid hormone synthesis (overview)
- Cholic acid
Test yourself
Think of the answer, then tap the question to see it.
Which three groups of molecules are made from cholesterol?
Steroid hormones, bile acids and vitamin D (from 7-dehydrocholesterol).
How does the body get rid of cholesterol if it does not oxidise it to CO₂?
It excretes it in bile, both as free cholesterol and converted to bile acids.
Why does cholesteryl ester sit in the lipoprotein core?
Without the free OH it is fully hydrophobic and cannot stay on the water-facing surface.
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: Cholesterol (CID 5997) (PubChem, NCBI, 2026) · Public domain; Cholesterol | High Cholesterol | MedlinePlus (MedlinePlus, US National Library of Medicine, 2026); High blood cholesterol levels: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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