Sterol

A sterol is any organic compound with a skeleton closely related to cholestan-3-ol. The simplest sterol is gonan-3-ol, which has a formula of C
₁₇H
₂₈O, and is derived from that of gonane by replacement of a hydrogen atom on C3 position by a hydroxyl group. It is therefore an alcohol of gonane.^[1][2][3]

More generally, any compounds that contain the gonane structure, additional functional groups, and/or modified ring systems derived from gonane are called steroids. Therefore, sterols are a subgroup of the steroids. They occur naturally in most eukaryotes, including plants, animals, and fungi, and can also be produced by some bacteria (however likely with different functions). ^[4][5] The most familiar type of animal sterol is cholesterol, which is vital to the structure of the cell membrane, and functions as a precursor to fat-soluble vitamins and steroid hormones. While technically alcohols, sterols are classified by biochemists as lipids (fats in the broader sense of the term).

Some sources make a distinction between sterols and stanols. In this context, the difference between them is analogous to the difference between cholesterol and cholestanol, in that sterols have a double bond between C-5 and C-6, while stanols have not.^[6][a]

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