So the first question is, what is the role that zinc actually plays? So, what zinc actually does is by reacting with the water, it transforms water into a much better nuclear file. And because water will be a much better nuclear file as a result of this interaction, it will be able to react with the carbon dioxide at a much higher rate and so will produce these bicarbonate ions, as we'll see in just a moment, at a much higher rate. So, to see what we mean, let's compare the PKA values of these two reactions. So, remember, the lower the PKA value, the better the acid. Now, if we take just plain water and we allow water to dissociate into H plus ions and these hydroxide ions, the PTA value is 15.7.