Cofactors and Coenzymes

 Many enzymes require non-protein substances to function. Without them the enzymes would not work efficiently.  There are two types of these enzyme helpers:

 1) Cofactor: inorganic molecules, minerals, usually metal ions. For instance magnesium is important in reactions where a phosphate group is transferred. One example of this is reversible reaction of ATP.
These cofactors can turn enzymes on and off or modify the rate at which enzymes work. Iron is another example.  Iron is an integral part of hemoglobin's ability to transport oxygen,

2) Coenzymes: organic compounds like vitamins. Coenzymes bind to specific site on a protein molecule and provides chemical functions that a protein alone cannot provide.  You body can make the necessary enzymes, but not the necessary minerals and vitamins which must be included in the diet.