Fatty acids are carboxylic acids with 12 to 20 carbon atoms in the chain. In general, animal fats are more saturated and plant oils are more unsaturated. Steroids are another class of lipids. All steroids contain a tetracyclic ring system. One steroid produced by your body is cholesterol.
Some important vitamins are lipids.
Vitamins are substances used by living cells to aid enzyme reactions. Your body uses vitamins in ways ranging from the synthesis of pigments needed for good vision to the red pigment in hemoglobin that carries oxygen in the blood. However, these large polymers are the largest single molecules in the body. Together, DNA and RNA store and transfer genetic information. The diagram at the top of this page is a very small segment of the structural formula for one DNA molecule.