=Cofactors= A cofactor is a non-protein chemical compound that is required for the protein's biological activity. Many enzymes require cofactors to function properly. Cofactors can be considered "helper molecules" that assist enzymes in their action. Cofactors can be ions or organic molecules (called coenzymes). Organic cofactors are often vitamins or are made from vitamins. Small quantities of these vitamins must be consumed in order for our enzymes to function correctly. [image:http://i.imgur.com/d3ikJnz.png?2] '''Mechanism of Action''' Many cofactors will sit in the enzyme active site and assist the binding of the substrate. An inactive enzyme without the cofactor is called an apoenzyme, while the complete enzyme with cofactor is called a holoenzyme.