Biochemistry is the study of chemical processes in living organisms, often referred to simply as biochemistry. It is mainly used to study the structure and function of various components in cells, such as proteins, sugars, lipids, nucleic acids and other biological macromolecules. For chemical biology, the emphasis is on the use of chemical synthesis methods to solve the relevant problems found in biochemistry. Although there are a large number of different biomolecules, there are actually many large complex molecules (called "polymers") that are formed from similar subunits (called "monomers") bound together. Each class of biopolymers has its own set of subunit types. For example, proteins are made up of 20 amino acids, while deoxyribonucleic acid (DNA) is made up of four nucleotides.