So these two proteins contain a special prosthetic group known as the hein group that assists the protein in actually binding the oxygen. And the heme group has the following structure. So the heme group consists of two components. It has the organic component known as protoporphy that contains the carbon atoms, the nitrogen atoms, the hydrogen atoms and the oxygen atoms. And this entire region, shown in black, is the protoporphine. It's the organic component of that Hen group.