A vast array of biomolecules is present in the cell. The structure of each biomolecule determines in what chemical reactions it is able to participate, and hence what role it plays in the cell's life processes. Among the most important classes of biomolecules are nucleic acids, proteins, carbohydrate s, and lipids. Nucleic acids are responsible for storing and transferring genetic information. They are enormous molecule s made up of long strands of subunits, called bases, that are arranged in a precise sequence.
Proteins are large molecules built up of small subunits called amino acids .
Using only 20 different amino acids, a cell constructs thousands of different proteins, each of which has a highly specialized role in the cell. These enzymes serve as promoters, or catalyst s, of chemical reactions. Carbohydrates are the basic fuel molecules of the cell. They contain carbon, hydrogen , and oxygen in approximately equal amounts. Animals, however, obtain their carbohydrates from foods.