AAAS: THE LIVING ENVIRONMENT: CELLS - The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins
The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins. Protein molecules are long, usually folded chains made from 20 different kinds of amino-acid molecules. The function of each protein molecule depends on its specific sequence of amino acids and the shape the chain takes is a consequence of attractions between the chain's parts.