And so we have to add two carbon atoms, and that's exactly what we do in cytrate. So step one, oxalo acetate and acetyl coenzyme A react to form citro coenzyme A, which then reacts with water to form the citrate. The purpose of this step is to create a molecule that will ultimately undergo the decarboxylation reactions. Now let's move on to step number two. In step number two, we see that the citrate cannot actually undergo the decarboxylation directly because the hydroxyl group on citral is not positioned on the correct location. And so what we do is we use a special type of enzyme that transforms the citrate into ISO citrate, which basically is an isomer of this molecule.