So two were used here. And now the third one we're using in this particular step. So we have the enzyme transketilase, which actually requires a cofactor we call Thiamine pyrophosphate. And we'll talk about the mechanism of this enzyme and what this actually does in the next lecture. But basically what the transketulase actually does, it takes a two carbon group from the zelulose. It takes this entire section, places it onto the ribbon.