In this case, because we used the Xyulose phyphosphate and the ribose phyphosphate. This product is the cetohptylos seven phosphate molecule. It's the ketos product. So in the final step, we want to reform this initial Thiamine Pyrophosphate in the protonated form. And so the H atom that was kicked off is basically picked up by this carbon atom to reform that protonated Thiamine pyrophosphate molecule. So we see that in this six step process, what ultimately happens is the transketulase uses that prosthetic group, the thymine pyrophosphate, to help transfer a two carbon group from the Xylose phyphosphate, the keto substrate, molecule two, that Aldo substrate, that ribose phyphosphate.