Only one end of a fatty acid is polar. A fatty acid consists of a polar carboxylic head group and a nonpolar hydrocarbon tail. Most fatty acids have an overall nonpolar character due to the long hydrocarbon chain; however, fatty acids with shorter hydrocarbon chains have an overall polar character.
The hydrocarbon chain length varies from 10 to 30 carbons, with the most common being 12 to 18 carbons in length. A fatty acid can be either saturated or unsaturated. A saturated fatty acid contains only single bonds; an unsaturated fatty acid contains one or more double bonds. Saturated fatty acids have a higher melting point than unsaturated fatty acids.