1. Recall from the class that we discussed the time required for molecules to diffuse across a certain distance. Conside

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1 Recall From The Class That We Discussed The Time Required For Molecules To Diffuse Across A Certain Distance Conside 1 (102.83 KiB) Viewed 66 times

1. Recall from the class that we discussed the time required for molecules to diffuse across a certain distance. Considering the one-dimensional diffusion case ( dRMS 1D=v2Dt ), how long does it take for Ca2+ to diffuse d=(1, 10, 100 and 1000 um)? Note that the diffusion coefficient for Ca2+ is Dca=0.8 x 10-5 cm2 s-1. What implication can you draw from your calculations? = 2. Recall from our discussion on the time required to abolish a concentration gradient across the membrane ([C] - [C].). We came up with an equation t= 1/k, where t is a time constant that tells us how long it would take to have the gradient dropped to 1le (37%) of the initial level. k is a rate constant and equals the permeability (P) times the surface-to-volume ratio. (a) For a spherical cell with a diameter of 30 um, calculate the t for glucose (Pglucose = 10-7 cm/s) and Nat (PNa+ = 10-13 cm/s). (b) Calculate again for a flat, cuboid cell with dimensions 30x30x3.14 um. (c) What do you learn from these calculations?