The heme portion of the hemoglobin molecule consists of:: (A) Porphyrin ring with a molecule of Fe in the center, (B) A polypeptide chain containing Fe, (C) A pyrole ring with four molecules of Fe in the center, (D) Four porphyrin rings, each containing a molecule of Fe in the center
Answer is D. Structurally, porphyrin consists of four pyrrole rings (five-membered closed structures containing one nitrogen and four carbon atoms) linked to each other by methine groups (−CH=).
The iron atom is kept in the centre of the porphyrin ring by interaction with the four nitrogen atoms.