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': 'Rate limiting step in facilitated diffusion? \nSelect and explain. \nA. Availability of contranspo, B. Conformational change in transpoer, C. Synthesis of carrier protein, D. Polarization of solute', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is'b'i.e., Conformational change in transpoer(Ref: Essentials of membrane Biophysics p. 25I).The relative slowness of the rate constant for conformational change reorienting the Solute-unoccupied transpoer (Step-4) makes it the rate-limiting step in the process of facilitated diffusion.", 'role': 'assistant'}]