Lipids are naturally occurring compounds that do not dissolve in water; we encounter them as oils, waxes or fats. They are usually represented on paper as line structures, and have two major classes. Saponifiable lipids are long chains of fatty acids; these break down with alcohol-based compounds like acetone. Nonsaponifiable substances are fat-soluble; the most famous of these is cholesterol.
Sterol is a Ring Structure
Cholesterol is a member of the sterol family, the only lipid classified as a ring structure. In fact, it has a ring "system" of tetracycline elements; one of the rings joins back on itself in a double bond, thus fortifying the steroid properties of the element.
Sterols Besides Cholesterol
Cholesterol is the only sterol lipid found in any measurable quantity in animals. However, other members of the "ring structure lipid" family -- all of which promote healthy and nutritious benefits to foods -- include sitosterol, stigmasterol, avenasterol, campesterol and brassicasterol. These are all found in plants, particularly canola sprouts, which accounts for the oil's popularity.