In this video, we're going to introduce cofactors. Some enzymes require what are known as cofactors, which are defined as non-protein substances required by an enzyme for catalysis to occur. If there is no cofactor, in some substances, no enzyme catalysis can take place. You can think of cofactors as basically little enzyme helpers— they help the enzyme perform enzyme catalysis.
Not all enzymes have cofactors, but some enzymes 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're not made up of amino acids like proteins are; instead, they're 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 actually assist with enzyme catalysis in many different ways, and we'll be able to see an example of how they can assist down below in our image. A coenzyme sounds a lot like a cofactor because it is a cofactor. A coenzyme is a very specific type of cofactor, defined as an organic molecule cofactor.
If the cofactor is an organic molecule, meaning that it contains 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 just made up of metal atoms; they 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 below to get a better understanding of how cofactors can assist enzymes with catalysis. Some cofactors can assist in substrate binding. In our image below, 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 perfectly tailored for this substrate and perhaps the substrate in some scenarios could not bind to the active site because the active site is not perfectly tailored for the substrate. If that happens, then the enzyme will not be able to perform catalysis. However, if a cofactor is present, such as this orange structure representing the cofactor, then the cofactor can bind into the active site.
Notice here, the cofactor is bound to the active site, which could make the active site better suited and better tailored for the substrate. Only in the presence of the cofactor will the substrate be able to bind into the active site. Once the substrate has bound into the active site, as shown on the far right, then 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 required to help enzymes perform catalysis. We'll be able to get some practice applying these concepts as we move forward in our course.
So I'll see you all in our next video.