sterol

of two types, phospholipids and sterols (generally cholesterol). Both types share the defining characteristic of lipids—they dissolve readily in organic solvents—but in addition they both have a region that is attracted to and soluble in water. This “amphiphilic” property (having a dual attraction; i.e., containing both a lipid-soluble and a…

of two types, phospholipids and sterols (generally cholesterol). Both types share the defining characteristic of lipids—they dissolve readily in organic solvents—but in addition they both have a region that is attracted to and soluble in water. This “amphiphilic” property (having a dual attraction; i.e., containing both a lipid-soluble and a…

Sterols are unique among lipids in that they have a multiple-ring structure. The well-known sterol cholesterol is found only in foods of animal origin—meat, egg yolk, fish, poultry, and dairy products. Organ meats (e.g., liver, kidney) and egg yolks have the most cholesterol, while…

, sterols) than do other animals. Some of these sterols (e.g., clionasterol, poriferasterol) are found only in sponges; others (e.g., cholesterol) are common in other animals. Numerous carotenoid pigments occur in sponges, and melanin, chlorophyll, and phycoerythrin derived from algal symbionts and from the diet also…

The most generally abundant steroids are sterols, which occur in all tissues of animals, green plants, and fungi such as yeasts. Evidence for the presence of steroids in bacteria and in primitive blue-green algae is conflicting.

A large group, the sterols, is composed of the common 3-monohydroxy steroids of the cholestane, ergostane, and stigmastane series and their methyl sterol biogenetic precursors: lanosterol, cycloartenol, and certain derivatives of these sterols, such as lophenol. Most sterols have a 3β-hydroxyl group, and many…

by ultraviolet radiation (sunlight) of sterols present in the skin.