Glycerol and Fatty Acids
One major class of lipids is called glycerolipids. Glycerolipids are composed of glycerol and fatty acids. Glycerol
, whose structural formula is shown at right, has three carbon atoms, each of which has a hydroxyl (-OH) group bound to it.
are fairly long linear hydrocarbon chains with a carboxylic acid group at one end. Fatty acids are named based on the number of carbon atoms and carbon-carbon double bonds in the chain.
Move your mouse over the sample fatty acids below to see their names.
Note that in the structure of lauric acid, all the carbon-carbon bonds are single bonds. This means that no more hydrogen can be added to it. In other words, the molecule is saturated with hydrogen. In contrast, palmitoleic acid has a carbon-carbon double bond. This bond could bind a molecule of hydrogen, forming a 16-carbon molecule with no carbon-carbon double bonds. In other words, palmitoleic acid is unsaturated, since it is still able to bind additional hydrogen. Lipids made from saturated and unsaturated fatty acids have different properties, as you will discover on the next page.