Sterol

A sterol is a steroid lipid with a hydroxyl group, a fused four-ring structure, and a hydrocarbon side chain. Sterols are components of cell membranes and precursors to other molecules.

Steroid: A family of lipids built around four fused carbon rings, including sterols, steroid hormones, and bile acids. Sterols are the steroid members distinguished by a hydroxyl group and side chain.
Cell membrane: A selectively permeable lipid-and-protein boundary surrounding a cell. Sterols reside between membrane lipids and influence the boundary's physical properties.
Steroid hormone: A signaling molecule derived from cholesterol that regulates processes such as metabolism, reproduction, and stress responses. Cholesterol is the starting material for these hormones.
Sterol ester: A sterol whose hydroxyl group is esterified to a fatty acid or another acid. Esterification removes the free hydroxyl that distinguishes an unmodified sterol.
Hydroxyl group: A functional group consisting of an oxygen atom bonded to a hydrogen atom. Its polar hydroxyl group gives sterols a water-interacting end.
Lipid bilayer: A double layer of amphipathic lipids that forms the basic structure of many biological membranes. Sterols insert among its lipids, with their hydroxyl groups near the aqueous surfaces.
Bile acid: A cholesterol-derived molecule that helps digest and absorb dietary fats in the intestine. The liver converts cholesterol into bile acids for fat digestion.
Stanols: Saturated derivatives of sterols in which one or more carbon–carbon double bonds have been reduced. Stanols resemble sterols but differ in the saturation of their ring structure.
Cholesterol: An animal sterol that stabilizes cell membranes and serves as a precursor to steroid hormones and bile acids. It is the best-known example of the sterol structure.
Membrane fluidity: The mobility of molecules within a biological membrane, influenced by lipid composition and temperature. Sterols buffer changes in lipid movement as temperature shifts.

Linked from 8 pages