Cofactors-The first type of enzyme partner is a group called cofactors, or molecules that increase the rate of reaction or are required for enzyme function. Cofactors are not proteins but rather help proteins, such as enzymes, although they can also help non-enzyme proteins as well. Examples of cofactors include metal ions like iron and zinc.

Coenzymes-A specific type of cofactor, coenzymes, are organic molecules that bind to enzymes and help them function. The key here is that they're organic. 'Organic' does not mean you'll find them in a special aisle in the grocery store. Rather, organic molecules are simply molecules that contain carbon. Don't let the name 'coenzymes' fool you, either; coenzymes are not really enzymes. As the prefix 'co-' suggests, they work with enzymes. Many coenzymes are derived from vitamins.These molecules often sit at the active site of an enzyme and aid in recognizing, attracting, or repulsing a substrate or product. Remember that a substrate is the molecule upon which an enzyme catalyzes a reaction. Coenzymes can also shuttle chemical groups from one enzyme to another enzyme. Coenzymes bind loosely to enzymes, while another group of cofactors do not.