So to see how that takes place, let's take a look at the following diagram. So, in this diagram to the left, we have the alpha helix of one of the polypeptide chains. And this alpha helix is attached to this heme group. So remember, the heme group shown here consists of the organic component that is known as the protoporphrine. And it also contains that inorganic metal atom, that iron atom. Now, the iron atom is attached to the proximal HistoGene amino acid that is attached to this polypeptide chain.