Biochemistry is the study of the chemical processes and transformations in living organisms. It deals with the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules. Chemical biology aims to answer many questions arising from biochemistry by using tools developed within synthetic chemistry.
Although there are a vast number of different biomolecules, many are complex and large molecules (called polymers) that are composed of similar repeating subunits (called monomers). Each class of polymeric biomolecule has a different set of subunit types. For example, a protein is a polymer made up of 40 or more amino acids. Biochemistry studies the chemical properties of important biological molecules, like proteins, in particular the chemistry of enzyme-catalyzed reactions.
The biochemistry of cell metabolism and the endocrine system has been extensively described. Other areas of biochemistry include the genetic code (DNA, RNA), protein synthesis, cell membrane transport, and signal transduction.
This article only discusses terrestrial biochemistry (carbon- and water-based), as all the life forms we know are on Earth. Since life forms alive today are hypothesized by most to have descended from the same common ancestor, they would naturally have similar biochemistries, even for matters that seem to be essentially arbitrary, such as handedness of various biomolecules. It is unknown whether alternative biochemistries are possible or practical.