Now, in this particular case, this fe atom has 12345 bonds. And what that means is it can form one more bond with some other Atom. And so on. The top portion of that fe, that is exactly where that bond will be formed between the diatomic oxygen and that metal atom. Remember, it's this metal iron atom of the hemegroup that binds directly and holds onto that diatomic oxygen. So if this is the unbound state of our protoporphy, then when the oxygen actually binds, what happens is this diatomic oxygen moves from the top position of that fe, and it begins to pull away some of that electron density from that metal atom.