In diagram one, we basically have the inorganic orthophosphate that goes into the active side along with the succinl coenzyme a. So we have the succinct coenzyme a, we have the orthophosphate. And notice the GDP is not found in this location. In fact, the GDP is found nearby, but not in the same location. And we'll see what happens in the final two steps that allows us to actually bring that orthophosphate to that GDP. So in the first step, what happens is the inorganic orthophosphate actually acts as a nucleophile.