This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'In hemoglobin, the innate affinity of heme for carbon monoxide is diminished by the presence of : \nSelect and explain. \nA. His F8, B. His E7, C. Gly B6, D. Thr C4', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The heme has high affinity for carbon monoxide (about 25000 more than for 02). But when heme molecule is associated with Histidine E 7 (as occurs in myoglobin), its affinity for CO is drastically reduced because His E 7 creates a hindered environment for CO by disturbing the orientation of atoms in heme molecules.', 'role': 'assistant'}]