CID 5997

C₂₇H₄₆O

Cholesterol

C 27
H 46
O 1

Ball-and-stick Stick Space-filling

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74 atoms, 77 bonds.

IUPAC name: (3S,8S,9S,10R,13R,14S,17R)-10,13-dimethyl-17-[(2R)-6-methylheptan-2-yl]-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-3-ol
Molar mass: 386.664(64) g/mol
Atoms: 74
SMILES: CC(C)CCCC(C)C1CCC2C1(CCC3C2CC=C4C3(CCC(C4)O)C)C
InChIKey: HVYWMOMLDIMFJA-DPAQBDIFSA-N
PubChem CID: 5997

Made of

C H O

Structural formula of cholesterol. Each unlabelled corner is a carbon atom, and the 30 hydrogens on carbon are not drawn. Wedges come toward you, hashes go back. It shows which atoms are joined to which, not the shape. The model above shows the shape.

Among the steroids, cholesterol is the most common, on the count of OpenStax Biology. Like every steroid it is built on four linked rings of carbon, and like several of them it has a short tail. The whole molecule, C₂₇H₄₆O with a molar mass of 386.7 g/mol, holds just one atom of oxygen among its carbons and hydrogens.

OpenStax groups steroids such as cholesterol with the lipids, which are largely nonpolar because their bonds are mostly carbon–carbon and carbon–hydrogen. Nonpolar molecules are hydrophobic, meaning they do not mix with water. Hazardous Substances Data Bank (HSDB) data on PubChem put cholesterol’s solubility at 0.095 mg per litre at 30 °C. It dissolves instead in oils, fats, benzene and solutions of bile salts.

The pure substance forms white or faintly yellow pearly crystals that melt at 148.5 °C. The lone oxygen belongs to an –OH group, which places cholesterol among the alcohols; steroids of that kind are called sterols.

Structure and bonding

Cholesterol’s 74 atoms and 77 bonds fall into three parts. Four rings are fused edge to edge, with a branched hydrocarbon tail at one end and the –OH group at the other. Every carbon–carbon bond is single except one. That double bond sits in the second ring and is the “5-en” in cholest-5-en-3-ol, the name chemical inventories such as the US EPA’s list use. With Labels switched on, the single O stands out among 27 C and 46 H.

In the Space-filling view the hydrogens wrap the carbon frame almost completely. The oxygen’s red sphere sits at one end; in PubChem’s computed model its centre lies about 14.5 Å (an ångström is 10⁻¹⁰ m) from the farthest carbon. The Stick view thins everything to lines, which makes the ring junctions easy to trace.

Larger molecules, OpenStax Chemistry notes, have no single central atom, only local geometries around interior atoms. No one VSEPR (valence-shell electron-pair repulsion) shape word fits cholesterol. The model draws the neutral free sterol, and that is its real bonding: no aromatic ring, no resonance form, no charge. Cholesteryl esters, the form in which the body stores some of it, are separate compounds.

Where it turns up

HSDB, on PubChem, finds cholesterol in all body tissues, above all in the brain and spinal cord, and in animal fats and oils. It is also the main constituent of gallstones. Inside a cell, the Human Metabolome Database (HMDB) lists it in the membranes, the endoplasmic reticulum, the mitochondria, lysosomes and the Golgi apparatus. The Toxin and Toxin Target Database (T3DB) names the foods that supply it: meats, eggs, milk, cheese, fish and shellfish.

The commercial product comes from the spinal cords of cattle and from wool grease. HSDB notes that cholesterol taken from animal organs always contains cholestanol and other saturated sterols as impurities. Pharmaceutical and skin preparations use it as an emulsifying agent, an ingredient that holds oil and water together in one cream. The NORMAN database lists its cosmetic roles as stabilising, emulsifying and emollient, and personal-care products contain it, according to a US consumer-product database.

Why it matters

A body gets cholesterol by absorbing it from food or by making it. OpenStax names the liver as a maker, and its anatomy text places the same process in fat cells too. Its carbons come from acetyl coenzyme A (acetyl CoA), a molecule made when the body breaks down glucose, through an intermediate called hydroxymethylglutaryl CoA (HMG CoA). The liver turns it into bile salts, which help emulsify dietary fats for absorption. It yields steroid hormones such as testosterone and estradiol; vitamin D comes from its precursor, 7-dehydrocholesterol, MeSH and MedlinePlus Genetics explain.

Chylomicrons, particles of triglyceride, phospholipid and protein, move water-insoluble cholesterol, free and esterified, from the intestine through the lymph into the watery bloodstream. In the blood it also travels in other lipoproteins, the LDL and HDL (low- and high-density lipoproteins) that HSDB names. Only the liver has the enzymes to break down significant amounts, mainly into cholic acid and chenodeoxycholic acid. Bile acids were once thought to carry about 90 per cent of all elimination. T3DB adds a second route, trans-intestinal cholesterol efflux, straight into the intestine.

Properties

Properties of cholesterol Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 5997.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₂₇H₄₆O
Molar mass	386.664(64) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	27
Hydrogen atoms	46
Oxygen atoms	1
Bonds	77
Single bonds	76
Double bonds	1
PubChem molecular weight	386.7 g/mol	g/mol	PubChem

Safety

As a pure substance, cholesterol is essentially harmless. Of 227 company reports to the European Chemicals Agency (ECHA), gathered on PubChem, 97.8% find that it meets no GHS (Globally Harmonized System) hazard criteria. Blood cholesterol is a medical question for a doctor, not a hazard of the chemical. The PubChem Laboratory Chemical Safety Summary is the sheet for the substance itself.

Questions

Where is cholesterol found in a cell?

Mainly in its membranes. OpenStax Biology says sterols are components of the plasma membrane and sit within the phospholipid bilayer, the double layer of phospholipids that is the major component of all cell membranes. Animal cells use cholesterol there, and plants use phytosterols. The Toxin and Toxin Target Database calls it essential for membrane integrity, and the Human Metabolome Database also places it in the endoplasmic reticulum, mitochondria, lysosomes and Golgi apparatus.

Why doesn't cholesterol dissolve in water?

Its 27 carbons and 46 hydrogens are joined mostly by carbon-carbon and carbon-hydrogen bonds, which OpenStax describes as nonpolar. Lipids built that way are hydrophobic, and HSDB data on PubChem put cholesterol's solubility at only 0.095 mg per litre at 30 °C. From the intestine it travels through lymph and blood inside chylomicrons, particles of fat, phospholipid and protein; other lipoproteins such as LDL and HDL also carry it in blood.

Is cholesterol bad for you?

OpenStax Biology stresses that the body needs cholesterol to work properly, whatever its everyday reputation. The concern is with how it travels in blood. A raised LDL level, the low-density lipoprotein often called the 'bad' kind, may lead to plaque in the arteries and so to heart disease. Unsaturated fats help lower blood cholesterol, and dietary fibre binds cholesterol in the small intestine and keeps it out of the bloodstream.

What do plants have instead of cholesterol?

Plant cell membranes hold related sterols called phytosterols in the place where animal membranes hold cholesterol, according to OpenStax Biology. The Merck Index, quoted on PubChem, calls cholesterol the main sterol of higher animals. T3DB lists the foods it is found in as animal products: meats, eggs, milk, cheese, fish and shellfish.

Made of the same elements

C₂₇H₄₄O Cholecalciferol 72 atoms, 74 bonds.
C₁₈H₃₄O₂ Oleic acid 54 atoms, 53 bonds.
C₂₁H₃₀O₂ Progesterone 53 atoms, 56 bonds.
C₂₁H₃₀O₅ Cortisol 56 atoms, 59 bonds.
C₁₆H₃₂O₂ Palmitic acid 50 atoms, 49 bonds.
C₁₉H₂₈O₂ Testosterone 49 atoms, 52 bonds.
C₁₈H₂₄O₂ Estradiol 44 atoms, 47 bonds.
C₂₀H₁₄O₄ Phenolphthalein 38 atoms, 41 bonds.

All 51 compounds made of carbon, hydrogen and oxygen

C₁₅H₁₆O₂ Bisphenol A 33 atoms, 34 bonds.
C₁₃H₁₈O₂ Ibuprofen 33 atoms, 33 bonds.
C₁₀H₂₀O Menthol 31 atoms, 31 single bonds.
C₁₄H₁₄O₃ Naproxen 31 atoms, 32 bonds.
C₁₂H₂₂O₁₁ Lactose 45 atoms, 46 single bonds.
C₁₂H₂₂O₁₁ Sucrose 45 atoms, 46 single bonds.
C₄H₉OH 1-Butanol 15 atoms, 14 single bonds.
C₉H₈O₄ Aspirin 21 atoms, 21 bonds.
C₂H₅OC₂H₅ Diethyl ether 15 atoms, 14 single bonds.
C₈H₈O₃ Methyl salicylate 19 atoms, 19 bonds.
C₈H₈O₃ Vanillin 19 atoms, 19 bonds.
C₆H₅CHO Benzaldehyde 14 atoms, 14 bonds.
C₆H₁₂O₆ Fructose 24 atoms, 24 single bonds.
C₆H₁₂O₆ Glucose 24 atoms, 24 single bonds.
C₆H₅COOH Benzoic acid 15 atoms, 15 bonds.
C₄H₈O Butanone 13 atoms, 12 bonds.
C₆H₅OH Phenol 13 atoms, 13 bonds.
C₃H₇OH 1-Propanol 12 atoms, 11 single bonds.
C₃H₇COOH Butyric acid 14 atoms, 13 bonds.
CH₃COOC₂H₅ Ethyl acetate 14 atoms, 13 bonds.
C₃H₈O Isopropyl alcohol 12 atoms, 11 single bonds.
C₇H₆O₃ Salicylic acid 16 atoms, 16 bonds.
C₃H₈O₂ Propylene glycol 13 atoms, 12 single bonds.
C₃H₆O Acetone 10 atoms, 9 bonds.
C₆H₈O₆ Ascorbic acid 20 atoms, 20 bonds.
C₃H₈O₃ Glycerol 14 atoms, 13 single bonds.
C₆H₈O₇ Citric acid 21 atoms, 20 bonds.
CH₃OCH₃ Dimethyl ether 9 atoms, 8 single bonds.
C₂H₅OH Ethanol 9 atoms, 8 single bonds.
C₂H₅COOH Propionic acid 11 atoms, 10 bonds.
C₂H₆O₂ Ethylene glycol 10 atoms, 9 single bonds.
C₃H₆O₃ Lactic acid 12 atoms, 11 bonds.
CH₃CHO Acetaldehyde 7 atoms, 6 bonds.
C₂H₄O Ethylene oxide 7 atoms, 7 single bonds.
C₄H₆O₅ Malic acid 15 atoms, 14 bonds.
CH₃COOH Acetic acid 8 atoms, 7 bonds.
CH₃OH Methanol 6 atoms, 5 single bonds.
C₄H₆O₆ Tartaric acid 16 atoms, 15 bonds.
C₂H₄O₃ Glycolic acid 9 atoms, 8 bonds.
CH₂O Formaldehyde 4 atoms, 3 bonds.
HCOOH Formic acid 5 atoms, 4 bonds.
H₂CO₃ Carbonic acid 6 atoms, 5 bonds.
H₂C₂O₄ Oxalic acid 8 atoms, 7 bonds.