Chemistry. An organic acid molecule consisting of a chain of carbon molecules and a carboxylic acid group. Fatty acids are found in fats, oils, and as components of a number of essential lipids, such as phospholipids and triglycerides. Fatty acids are classified as saturated and unsaturated. A saturated fatty acid contains only single bonds in the carbon chain. An unsaturated fatty acid possesses one or more double or triple bonds in the carbon chain. These bonds are easily split in chemical reactions, and other substances may be joined to the carbon atoms involved.