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A '''fatty acid''' is an organic compound that is an important component of [[lipid]]s in [[plant]]s, [[animal]]s, and [[microorganism]]s. Fatty acids are [[carboxylic acid]]s with a long [[hydrocarbon]] chain, usually straight, as the fourth substituent group on the carboxyl (COOH) group that makes the molecule an acid. If the carbon-to-carbon bonds 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. A high level of saturated fatty acids in the diet raises blood [[cholesterol] levels. A few fatty acids have branched chains. Others (e.g., [[prostaglandin]]s) contain ring structures. Fatty acids in nature are always combined, usually with [[glycerol]] as [[triglyceride]]s 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.
[[Category:Biochemistry]]