[Fatty acids: their biochemical and functional classification].

Fatty acids (FA) constitute the main component of phospholipids, triglycerides and cholesterol esters. FA are acidic, monocarboxylic linear chains of variable length: short-chain FA (2-4 carbon atoms), medium-chain FA (6-12 carbon atoms), long-chain FA (14-18 carbon atoms), very long-chain FA (derived from parental 18-carbon molecules). They can be further subdivided into saturated (no double bond), monounsaturated (one double bond) and polyunsaturated (two or more double bonds). They are all involved in energetic, metabolic and structural activities. Short-chain FA act as growth factors; medium chain FA are readily available as energy source; saturated long-chain FA constitute a source of energy but may be implicated in the development of the atherosclerotic process; unsaturated long-chain FA include oleic acid and the essential fatty acids (linoleate and linolenate), and are all implicated in fundamental metabolic processes; very-long chain FA are the most characteristic molecules in biologic membranes. From recent works it is clearly established that the physiological role of FA depends on the chain length, and that the very-long chain molecules could determine the quality of human development. A functional classification of FA today must be based not only on the rate of unsaturation, but also (and most importantly) on the chain length.