In this video, we're going to introduce cofactors, and some enzymes require what are known as cofactors, which are non-protein substances required by an enzyme for catalysis to occur. If there is no cofactor, in some cases, no enzyme catalysis can take place. You can think of cofactors as basically little enzyme helpers. They help the enzyme perform catalysis. Not all enzymes have cofactors, but some do. An example of cofactors includes metal ions. Some enzymes will not be able to perform catalysis without metal ions, which are non-protein because they are not made up of amino acids like proteins. Instead, they are just metal ions. Cofactors are not consumed in the reaction, which means that at the beginning and by the end of the reaction, the cofactor remains the same. Cofactors can assist with enzyme catalysis in many different ways, and we will see an example below in our image.

A coenzyme sounds a lot like a cofactor, and that's because it is a specific type of cofactor. A coenzyme is an organic molecule cofactor. If the cofactor is an organic molecule, containing carbon and hydrogen atoms, then we refer to it as a coenzyme. Not all cofactors are coenzymes because not all cofactors are organic molecules. For example, metal ions are made up of metal atoms and do not contain carbon and hydrogen atoms. It's only the cofactors that are organic molecules that we call coenzymes. Coenzymes tend to be derived from vitamins.

Let's take a look at our example to get a better understanding of how cofactors can assist enzymes with catalysis. Some cofactors can assist in substrate binding. In the image on the left-hand side, notice that the enzyme is shown in red and the substrate in black. Notice that the enzyme's active site here is not ideally tailored for this substrate, so perhaps the substrate could not bind to the active site in some scenarios, and if that happens, the enzyme will not be able to perform catalysis. However, if a cofactor is present, such as the orange structure representing the cofactor, then the cofactor can bind to the active site. Notice here, the cofactor is bound to the active site, which could make the site better suited and better tailored for the substrate. Only in the presence of the cofactor will the substrate be able to bind to the active site. Once the substrate has bound to the active site, as shown on the far right, enzyme catalysis can proceed, and the enzyme can convert the substrate into the product, which is not shown here, but you can imagine the reaction continuing as normal.

This concludes our introduction to cofactors and how they are non-protein substances that are required to help enzymes perform catalysis. We'll get some practice applying these concepts as we move forward in our course, so I'll see you all in our next video.