Assume that glucose is transported across a membrane at 3 × 10–10 mol/(cm2·s). a
ID: 19786 • Letter: A
Question
Assume that glucose is transported across a membrane at 3 × 10–10 mol/(cm2·s).a) When the ratio of the concentration of glucose in the blood to the concentration of glucose in the cell is halved, what is the effect on the net rate of glucose transport into the cell?
a. The new rate is about 1.5 × 10^-10 mol/(cm^2·s).
b. The new rate is about 3 × 10^–10 mol/(cm^2·s).
c.The new rate is about 1.7 × 10^-5 mol/(cm^2·s).
d. The new rate is about 6 × 10^-10 mol/(cm^2·s).
hint:
J=[-KD1 (C2-C1)]/l
where J is the net rate of transport
K is the partition coefficient
D1 is the diffusion coefficient in cm2/s
C2–C1 is the concentration difference across the membrane
l is the thickness of the membrane in cm
Explanation / Answer
I think the new rate is (a). because in diffusion, the rate of transport is proportional to the difference in the concentrations. When CBlood/Ccell is halved (glucose is transported into the cell - so conc. in blood is higher than cell) either CBlood is directly halved or CCell is doubled or CBlood is decreased-CCell is increased proportionately such that the ratio is halved, then the diffusion rate has to decrease obviously. Hence I think it is (a), but even so i think it should be greater than (a).