In hemoglobin, iron is bound to: (A) Histidine, (B) Leucine, (C) Isoleucine, (D) Valine
Answer is A. The iron atom of hemoglobin has six coordinated bonds : (i) Four bonds are formed between the iron and nitrogen atoms of porphyrin ring system; (ii) Fifth bond is formed between the nitrogen of histidine (proximal histidine: HisF8) of globin; and (iii) Sixth bond is formed with oxygen.