HAEM: what is a haem?

This is a non-protein part of haemoglobin. It is an iron containing pigment. Its pigment part is called porphyrin. Four molecules of pyrole form one porphyrin. The pyroles are attached to each other by methane bridges. The iron is attached to each – N group of the pyrole and that of globin
i.e Hb + 4O2 —-> HbO8