And by the way, what is the difference between galactose and glucose? Well, galactose and glucose are epimers, and what that means is they only differ in the stereo chemistry at a single chiral carbon atom. So which one? Well, this carbon atom number four in galactose, it points up, in glucose, it points down. So it might seem that the only thing we have to do is basically flip this down. But that's not actually what happens because our cells follow a slightly more complicated pathway.