A group of polymers that have one characteristic in common, they do not mix with water. They are hydrophobic. Some important groups are fats, phospholipids, and steroids.
Fats: are large molecules composed of 2 types of monomers, glycerol ( an alcohol-containing 3 carbons) and 3 fatty acid molecules. The bond connecting the glycerol and fatty acids in the fat molecule is called an ester bond. There are two types of fatty acids: saturated and unsaturated. The saturated fatty acids do not contain any double bonds between the carbons, while the unsaturated fatty acids contain one or more double bonds between the carbons. These double bonds cut down on the number of hydrogen atoms that can be attached to the carbon in the molecule. This causes the molecule to bend or kink at each of the double bond sites.
Characteristics of Fats:
Saturated 1. solid at room temperature, 2. found mostly in animals, 3. no double bonds between carbons.
Unsaturated 1. liquid at room temperature, 2. found mostly in plants, 3. several double bonds between carbons.
The function of fats: acts as insulation in higher vertebrates, serves as an energy storage source 1g.=9 Kcal of energy, and shock absorber for internal organs.
Phospholipids: structurally related to fats but contain 2 fatty acids and one molecule of phosphate. These molecules are found making up the plasma membrane of cells. They exhibit a polar and nonpolar quality. The phosphate group is hydrophilic while the fatty acid area is hydrophobic.