And so the nitrogen in this Thiozol ring of the Thiamine pyrophosphate basically acts as an electron acceptor. It accepts those electrons, and it bears those two electrons in this intermediate molecule we call the activated glycoaldehyde. So we have the pi bond and the sigma bond between the carbon that came from this cellulose phyphosphate and this carbon here. Notice we kick off our one, two, three carbon molecule, the glyceroaldehyde three phosphate, and the remaining two carbon atoms remain on this activated glyceroaldehyde. Now, in the next step, we have the other substrate molecule basically coming in. So in this particular case, we're going to use ribose phyphosphate.