- fatty acid
Biochem.any of a class of aliphatic acids, esp. palmitic, stearic, or oleic acid, consisting of a long hydrocarbon chain ending in a carboxyl group that bonds to glycerol to form a fat.[1860-65]
* * *Organic compound that is an important component of lipids in plants, animals, and microorganisms.Fatty acids are carboxylic acids with a long hydrocarbon chain, usually straight, as the fourth substituent group on the carboxyl (―COOH) group (see functional group) that makes the molecule an acid. If the carbon-to-carbon bonds (see bonding) in that chain are all single, the fatty acid is saturated; artificial saturation is called hydrogenation. A fatty acid with one double bond is monounsaturated; one with more is polyunsaturated. These are more reactive chemically. Most unsaturated fats are liquid at room temperature, so food manufacturers hydrogenate them to make them solid (see margarine). A high level of saturated fatty acids in the diet raises blood cholesterol levels. A few fatty acids have branched chains. Others (e.g., prostaglandins) contain ring structures. Fatty acids in nature are always combined, usually with glycerol as triglycerides in fats. Oleic acid (unsaturated, with 18 carbon atoms) is almost half of human fat and is abundant in such oils as olive, palm, and peanut. Most animals, including mammals, cannot synthesize some unsaturated "essential" fatty acids; humans need linoleic, linolenic, and arachidonic acids in their diet.
* * *important component of lipids (fat-soluble components of living cells) in plants, animals, and microorganisms. Generally, a fatty acid consists of a straight chain of an even number of carbon atoms, with hydrogen atoms along the length of the chain and at one end of the chain and a carboxyl group (−COOH) at the other end. It is this carboxyl group that makes it an acid (carboxylic acid). If the carbon-to-carbon bonds are all single, the acid is saturated; if any of the bonds is double or triple, the acid is unsaturated and is more reactive. A few fatty acids have branched chains; others contain ring structures (e.g., prostaglandins). Fatty acids are not found in a free state in nature; commonly they exist in combination with the alcohol glycerol in the form of triglyceride (q.v.).The most widely distributed fatty acid is oleic acid, which is abundant in some vegetable oils (e.g., olive, palm, peanut, and sunflower seed) and which makes up about 46 percent of human fat.Many animals cannot synthesize one or more of the fatty acids and must ingest them in foods. Two such derived fatty acids are linoleic and linolenic acids; these, and sometimes arachidonic acid, which can be synthesized from linolenic, are required by all mammals and are called essential fatty acids.Soaps are the sodium and potassium salts of fatty acids.
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