Characteristics of Lipids

According to Michigan State University, lipids are organic compounds that are related by their solubility in benzene, chloroform, ether and acetone and their general insolubility in water. The American Oil Chemists Society says it is difficult to clearly define lipids and says lipids include fatty acids and their derivatives and substances related to these compounds. Each lipid group has distinctive characteristics.

Fatty Acids

The American Oil Chemists Society says fatty acids are straight chain carbon compounds with zero to three double bonds. They may be better recognized as saturated, monounsaturated and polyunsaturated fatty acids. Saturated fatty acids are long chain carbons without any bonds. Kathleen Mahan and Sylvia Escott-Stump, authors of "Food, Nutrition and Diet Therapy," say the longer the fatty acid chain and the more saturated it is, the harder the fat. Examples of saturated fats include the fat in meats (marbling seen in meat) and butter. Monounsaturated fatty acids contain only one double bond, making it more liquid at room temperature. Examples of monounsaturated fatty acids include olive oil and canola oil. Polyunsaturated fatty acids contain two or more double bonds and are also liquids at room temperature. Examples of polyunsaturated fatty acids include vegetable oil and soy oil. The essential fatty acids, omega-3 and omega-6, are polyunsaturated fatty acids.

Triglycerides

Michigan State University says triglycerides are composed of three fatty acids attached to a glycerol. Triglycerides are found in both plants and animals. Solid triglycerides are more commonly found in animals and contain more saturated fatty acids. Liquid triglycerides, or oils, are more commonly found in plants and contain more unsaturated fatty acids. According to Mahan and Escott-Stump, triglycerides serve as the major storage of energy in the body. Humans have several weeks' worth of stored triglyceride energy in adipose tissue. In addition to stored energy, triglycerides also act as an insulator to preserve body heat.

Sterols

The Michigan State University says sterols, or steroids, are a more complex lipid composed of five- and six-sided rings with individual side groups. The most commonly known sterol is cholesterol. Cholesterol is only found in animals, and according to Mahan and Escott-Stump, is an essential component of cell structure. Cholesterol is also a key player in the synthesis of bile, estrogen and testosterone. Cholesterol and ergosterol, another sterol, are precursors to the formation of Vitamin D.