And what happens in this reaction is an enzyme known as phosphoglycerate mutase, basically catalyzes the movement, the transfer of the phosphoryl group shown in blue from the third carbon onto this second carbon here. And so we go from three phosphaglycerate, two two phosphoglycerates. Now we'll talk about why that happens in just a moment. So whenever you hear the word mutase, what that should basically tell you is you're dealing with some type of enzyme that catalyzes a reaction in which it moves some type of group from one point on the molecule to a different point on that molecule. And so in this particular case, the mutase is a phosphoglycerate mutase. It moves a phosphoryl group within this phosphorylycerate molecule.