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. And enzymes are highly efficient and limit the number of unwanted products. So, for example, in the case of carbonic and hydrates, carbonic and hydrates binds the CO2 and the water, and the CO2 is the substrate. Now, CO2 can react with water in many different ways.