monomer

Chemical compound composed of simple molecules from which polymers can be made. Under certain conditions the simple molecules (of the monomer) join together (polymerize) to form a very long chain molecule (macromolecule) called a polymer. For example, the polymerization of ethene (ethylene) monomers produces the polymer polythene (polyethylene):

2nCH₂ CH₂®(CH₂CH₂ CH₂CH₂)_n

Large biomolecules are also assembled from monomers, for example proteins from amino acids, and starch from glucose. On a higher structural level, an entire protein can serve as a monomer for the assembly of complex molecular structures, for example in haemoglobin, where four identical protein subunits form a tetramer.