So we have historine residue one, two, and three, and they're bound to the zinc, as shown. And the final group is a water molecule. And this is the same water molecule that will react with the carbon dioxide to ultimately produce the bicarbonate. 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.