This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
[{'content': 'One molecule of Hb can bind to a maximum number of \nSelect and explain. \nA. Two molecules of oxygen, B. One molecule of oxygen, C. Four molecules of oxygen, D. Six molecules of oxygen', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Hemoglobins bind four molecules of O2 per tetramer, one per heme. A molecule of O2 binds to a hemoglobin tetramer more readily if other O2 molecules are already bound.Reference: Harper&;s Biochemistry; 30th edition; Chapter 6; Proteins: Myoglobin & Hemoglobin', 'role': 'assistant'}]