Now, the molecules or molecule that reacts with our enzyme is known as the substrate. And the substrate binds to a specific location on the enzyme known as the active site. And the interaction between our enzyme and the substrate is electric in nature. The force involved is electric in nature. Now, when the enzyme binds with our substrate this complex is known as the enzyme substrate complex. So in most cases, for the enzyme to actually function effectively and efficiently another type of molecule, a non protein molecule, has to bind to our enzyme and this molecule is known as a Cofactor.