In this module:

Formation of Fats and Oils

Glycerolipids are formed by joining fatty acids to glycerol by ester bonds, as shown below.

Click on the step numbers below to see the steps in glycerolipid formation. Click on the mouse icon at left to clear the images and text.

	The glycerol and fatty acids are oriented such that the hydroxyl and acid groups are close to each other.
1
	In an enzyme-catalyzed reaction, the hydroxyl oxygens of glycerol form a bond to the carboxyl carbons of the fatty acids, releasing water in the process.
2
	Ester bonds are left between glycerol and the fatty acids.
3

What aspect of the structure of a glycerolipid do you think might affect its melting point? Write your answer in the space provided, then click on the Check button to check your answer.

The lengths of the chains and the number of double bonds determine the melting point of a glycerolipid. Longer, saturated chains can pack against each other regularly, so there are stronger London forces between the chains, leading to a higher melting point. Shorter, unsaturated chains can't stack together as well, so there are fewer attractive forces between molecules, leading to lower melting points.

Lipids with a higher melting point are usually solids at room temperature and are called fats or waxes. Lipids with a lower melting point are usually liquids at room temperature and are called oils. Numerous studies have shown that a diet higher in oils than fats (shorter, unsaturated or polyunsaturated lipids) lead to a lower incidence of heart and pulmonary disease.