And so this reaction basically cycles back and forth and it takes place very quickly. And so every time this takes place, we produce a bicarbonate. So we transform our carbon dioxide into the bicarbonate which then dissolves into the cytoplasm inside our blood cells and into the blood plasma inside our cardiovascular system. So we see that the proteases we discussed previously were basically examples of Covalent catalysis and acid based catalysis. And in some cases, in the case of metalloproteases, they used the metal ion catalysis. But in the case of carbonic and hydrates these are examples of molecules which always use a metal atom, namely the zinc atom.