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': 'Hemoglobin acts as a buffer because of: \nSelect and explain. \nA. Glycine, B. Histidine, C. Alanine, D. Valine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Heamoglobin has 4 polypeptide chains, two identical a- chains and two identical p chains.Iron (Fe2+) of Hb is bound to histidine & four pyrrole rings.', 'role': 'assistant'}]