And we'll talk about that in detail in a future electra. Now, coenzymes can bind onto proteins either strongly or weakly. And if we have a coenzyme that is bound very tightly to the enzyme that is known as a prosthetic group number four enzymes are extremely efficient and extremely specific molecules. And what that means is enzymes only bind to specific substrate specific molecules and they carry out either a single reaction or a set of reactions that are closely related to one another. So enzymes bind to specific reactants. We also call substrates and catalyze a single reaction or a set of related reactions.