And we want to discuss the mechanism that this molecule actually uses to promote and catalyze this reaction. And what this reaction ultimately does is it hydrates the carbon dioxide. So water adds onto the carbon dioxide, and that ultimately produces the carbonic acid, which dissociates into bicarbonate ion and the H plus ion. So let's begin by taking a look at the active side of carbonic and hydrase II. So, in our discussion on the mechanisms of enzymes, we said that one mechanism that enzymes use is known as metal ion catalysis. And in metal ion catalysis, the active side of the enzyme uses some type of metal ion to basically form a strong nucleophile.