Heme is which porphyrin:: (A) Type I, (B) Type II, (C) Type III, (D) Type IV
Answer is C. The side chain groups in porphyrins may be arranged in four different structural configurations (I to IV). Only type I and type III series are found in nature and the porphyrins of type III series are not only more abundant but are also physiologically impoant in humans. Haem is a type III porphyrin.