Carbon, hydrogen and oxygen are all elements that make up lipids. Lipids are one of the four major groups of organic molecules. The other three are carbohydrates, proteins and nucleic acid (DNA). One of the key characteristics of lipids is that they do not dissolve in water.
The four main types of lipids are fats, steroids, waxes and phospholipids. Fats are composed of three fatty acid molecules and a glycerol molecule. Fats are either solid or liquid at room temperature, depending on their composition and structure. There are two main types of fats: saturated and unsaturated.
Steroids are built from cholesterol molecules, which are rings of carbon and hydrogen atoms.
Examples of steroids are cholesterol and hormones like estrogen and testosterone. Cholesterol is vital to the functioning of cell membranes. Hormones are chemical signals that regulate body function and development.
Waxes consist of one long fatty acid chain and a glycerol molecule. They are plastic and soft at room temperature and produced by animals and plants. Plants use waxes to prevent water loss, while animals have wax in their ears to protect the eardrum. Phospholipids are the molecules that make up cell membranes. They are very similar to fats in their chemical make-up.