The functional group in fats is the carboxylic acid group:
![[Carboxylic Molecule]](../../media/molecules/carboxylic.gif)
Fats or Lipids are often called fatty acids. Generally, fatty acids have a long hydrocarbon chain with a carboxylic acid group on the end. Saturated fats contain all single bonds in the hydrocarbon chain. Polyunsaturated fats contain some double bonds between carbon atoms in the hydrocarbon chain.
These fatty acids do not actually exist in that form in fats and oils; they are present in the form of esters, the result of a reaction between a carboxylic acid and an alcohol,glycerol. Glyderol is a compound which has three alcohol groups, and these combine with three fatty acid molecules to form a triglyceride. Triglycerides serve as energy storage compounds. Cholesterol is also a lipid found in the body.