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': 'A factor favouring the transport across a cell membrane \nSelect and explain. \nA. Polar substance, B. High concentration gradient, C. Thick membrane, D. Big particle size', 'role': 'user'}, {'content': 'Answer: B \nExplanation: • Simple diffusion refers to the diffusion of the molecule across the membrane following a concentration gradient or chemical gradient, but without the help of any carrier protein.\n• The rate of diffusion depends on the following factors : -\nA) The rate of diffusion is directly proportionate\ni) The concentration (chemical) gradient\nii) The cross-sectional area of the membrane through which diffusion takes place\niii) Lipid solubility of the substance\nB) The rate of diffusion is inversely proportionate \ni) The thickness of the diffusion membrane\nii) Size of the particle\niii) Charge or polarity of the substance\n• So, simple diffusion is favoured by small size, lipid solubility and absence of polarity (non-polar substance) and charge (neutral molecule) through a thin, large membrane where the concentration gradient is more.', 'role': 'assistant'}]