Carbohydrates
Carbohydrates are molecules generally made of carbon, hydrogen, and oxygen atoms. Commonly referred to as sugars and starches, these structures play important roles in metabolism and photosynthesis. They are used to store and release energy so that our body and that of all organisms may function. Glucose is probably the most well-known of the monosaccharides, or single sugars, because of its critical role in these organic processes. Sucrose, a disaccharide or double sugar, is also famous because of its role as common table sugar.

Lipids
The lipid group is a diverse one classified by its solubility, not its structure like other groups. Lipids are nonpolar molecules that dissolve in fat instead of water. The most common lipids are fats, oils, sterols, waxes, and phospholipids. In the body these structures are often found storing energy.

Proteins
Proteins are often complex, always important structures in an organism that perform many varied tasks. Some are enzymes, or organic catalysts that speed up bodily reactions that would otherwise occur too slowly or not at all. Others are binding proteins that carry material from one place to another. An example of this would be human hemoglobin, a substance that carries oxygen and carbon dioxide in our blood. Still others are structural proteins or other varieties.

A protein is a large molecule made of one or more polypeptides. A polypeptide is a long linear chain of amino acids. The basic structure of proteins, then can be understood as a particular arrangement of the twenty amino acids. These twenty simple building blocks can be arranged to form complex, useful structures much like the twenty-six letters of our alphabet can be rearranged to create a beautiful novel or poem.