Carbohydrates contain atoms of carbon, hydrogen and oxygen. There are two times as many hydrogen atoms as carbon or oxygen atoms, according to the Austin Community College.
The human body uses carbohydrates to fuel the nervous system and provide much-needed energy for the muscles. Carbohydrates also prevent the body from using protein as an energy source. The structure of a carbohydrate determines if it is a monosaccharide, disaccharide or polysaccharide. Monosaccharides, also called simple sugars, are used as the building blocks for disaccharides and polysaccharides. When two monosaccharides join together, they form a disaccharide. If more than two monosaccharides join together, they form a polysaccharide.