Most common elements in living things are carbon, hydrogen, nitrogen, and oxygen. Chemistry of carbon allows the formation of an enormous variety of organic molecules.
Functional groups are clusters of atoms with characteristic structure and functions.
Each small organic molecule can be a unit of a large organic molecule called a macromolecule. Polymers are the large macromolecules composed of three to millions of monomer subunits. Cellular enzymes carry out condensation and hydrolysis of polymers. This produces the water given off during a condensation reaction. Monosaccharides are simple sugars with a carbon backbone of three to seven carbon atoms.