A biomolecule, also referred to as a biological molecule, is any molecule that is both produced by a living organism and is essential for one or more biological processes. The four largest categories are carbohydrates, lipids, proteins and nucleic acids.
Biomolecules are typically organic compounds composed primarily of carbon, hydrogen, oxygen and nitrogen, with some also containing sulfur or phosphorus or both. However, there are also inorganic biomolecules, including water, some minerals, and some gases (e.g., oxygen and carbon dioxide).
Organic compounds that are not biomolecules include many synthetic and industrial chemicals as well as naturally occurring organic substances that do not participate in biological processes. Examples are plastics and hydrocarbons.
Biomolecules vary widely in size and structure, ranging from small and simple inorganic molecules to small organic molecules, such as vitamins and hormones, to large macromolecules, such as proteins and nucleic acids. Many are polymers, which consist of repeating monomer units.