Now, why would we want to transfer an H ion? Well, in some cases, if we transfer an H ion from one molecule to another molecule we basically create a strong nucleophile. And that strong nucleophile might be needed in that particular biological reaction. So by transferring hydrogen ion the active site may activate a nucleophile that is required in that catalysis process. Now, by transferring an H ion we can also actually stabilize different types of groups that might be found inside the active site that contain charges. And the transfer of H ions can also be used to increase the electrostatic interactions that take place within that active site and that can interstabilize things like the transition state inside that chemical reaction.