Enzymes. Most enzymes are globular proteins. Active site: the region of an enzyme surface to which a specific set of substrates binds. Substrate : ( the reactant ) a molecule upon which an enzyme acts. A substrate molecule must fit precisely into an active site.
CO2 + H2O ----- H2CO3
carbon dioxide + water ----- carbonic acid
The reaction is very slow in the absence of an enzyme called carbonic anhydrase. Perhaps 200 molecules of carbonic acid are formed in an hour in a cell.