Proteins Proteins are very complicated molecules made up of amino acids. The 20 amino acids can be arranged in any order to make a polypeptide made up of thousands of amino acids. Their potential for variety is extraordinary. This variety allows proteins to function as extremely specific enzymes that function in a cell's metabolism. Not all proteins are enzymes , but most enzymes are proteins.
Enzymes act as catalysts in the chemical reactions in cells.
A catalyst is a molecule which increases the rate of a reaction but is not the substrate or product of that reaction. A substrate is a molecule upon which an enzyme acts to yield a product. Enzymes are usually named for the substrate on which they act or the action which they perform. They are important metabolically. Sugars are the major energy storage molecules for living organisms.