<prompt> All are factors determining diffusion across membrane exceptTemperatureParticle sizeMembrane pore sizeConcentration gradient Repeat, 2008  <response>: Ans b particle size Ref: Vasudevan 4th ed pg J3, Guyton 48, Ganong 22nd ed pg 4Diffusion is affected by concentration gradient, temperature, and membrane pore size.The text given in Guyton about molecular size appears confusing, but it is clearly stated in Vasudevan andSreekumari that permeability does not depend on molecular sizepage 13.Many would have gone for option c - Temperature, but it is clearly stated in Guyton page 48 that Greater the temperature, greater is the thermal motion of molecules and ions in a solution, so that diffusion increases directly in proportion to temperatureDiffusionIt is the process by which a gas or a substance in solution expands, because of the motion of its particles, to fill all of the available volume Diffusion through a membrane depends on various factors. The concentration gradient is one of the most important factor that affect diffusion. The other factors are cross sectional area, thickness of the membrane, temperature and membrane pore size. Diffusion is guided by the Ficks law of diffusion.Ficks law of diffusion J - DA J is the net rate of diffusionD is the diffusion coefficientA is the areadC dX is the concentration gradientThe minus indicates the direction of diffusion. 