Lipids

LIPIDS

Figure 84.

Lipids can be fatty acids, which have a carboxylic acid end and a long hydrocarbon chain. Three fatty acid molecules are attached to glycerol to form what are known as “triglycerides”. These are the storage form of fatty acids. As you may know, there are saturated fatty acids, which have all the hydrocarbons saturated with hydrogen atoms, monounsaturated fatty acids, which have the loss of hydrogen atoms because of a double bond between carbon atoms, and polyunsaturated fatty acids, which have many double bonds in the fatty acid carbon chain. Figure 85 is a sampling of some fatty acids:

Figure 85.

Besides fatty acids, there are cholesterol-based molecules that are also called lipids. The basic structure of cholesterol is shown in figure 86:

Figure 86.

While cholesterol looks nothing like a fatty acid, it is still considered a lipid and is the backbone molecule to many lipid-soluble molecules, such as estrogen, progesterone, and testosterone—all important molecules in biochemical reactions in higher-order animals.