As the glycerol molecule in all triglycerides is the same, the differences in the properties of different fats and oils come from variations in the fatty acids. There are over 70 different fatty acids and all have a carboxyl (-COOH) group with a hydrocarbon chain attached. If this chain has no carbon-carbon double bonds, the fatty acid is then described as saturated, because all the caron atoms are linked to the maximum number of hydrogen atoms, in other words they are saturated with hydrogen atoms. If there is a single double bond, it is mono-unsaturated - if more than one double bond is present, it is polyunsaturated.