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: Physiology
[{'content': 'Hemoglobin unlike myoglobin showsa) Sigmoid curve of oxygen dissociationb) Positive cooperativityc) Hills coefficient of oned) None of above \nSelect and explain. \nA. ac, B. ab, C. ad, D. bc', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Hb-O2 dissociation curve- Sigmoid shape\nCo-operativity- Hb is a tetramer. If one molecule of O2 binds to the tetramer more easily if other O2 is already bound. \n\xa0\nHills coefficient of Hb- 2.8', 'role': 'assistant'}]