Now, Bicarbonate by itself is a stable molecule. It's low in energy. And so in the first step, what we want to do is we want to increase the energy of this molecule, make it more reactive. And so we use an ATP, we essentially phosphorylate this carbon and we form the carboxy phosphate. So now this molecule, unlike this one, has an additional negative charge and that makes it more reactive. Now, we also generate an ADP molecule that is not shown.