So actually, these two molecules are, in fact isomer. So, once again, the glyceroaldehyde phosphate lies directly on the glycolytic pathway, which means it could go on directly into stage three to form the ATP molecules, the Pyruvate and the nadhs, as we'll see in the next lecture. But the dihydroxyantone phosphate does not lie on that pathway directly. And this means that if the DHAP is not changed in any way, is not transformed into this gap molecule, then what will happen is we will not be able to continue that glycosis process and therefore it will not be used to form those high energy ATP molecule that the cell needs so much to actually carry out processes. And so to prevent the loss of this potential energy that is stored in this three carbon molecule, the DHAP has to transform that molecule into the gap. And this is where that second enzyme comes into play.