The Na –glucose symport system of intestinal epithelial cells couples the \\\"do
ID: 48365 • Letter: T
Question
The Na –glucose symport system of intestinal epithelial cells couples the "downhill" transport of two Na ions into the cell to the "uphill" transport of glucose, pumping glucose into the cell against its concentration gradient. If the Na concentration outside the cell ([Na ]out) is 161 mM and that inside the cell ([Na ]in) is 23.0 mM, and the cell potential is -53.0 mV (inside negative), calculate the maximum ratio of [glucose]in to [glucose]out that could theoretically be produced if the energy coupling were 100% efficient. Assume the temperature is 37 °C.
Explanation / Answer
The formula is deltaGchem=RTln([Na+in]/[Na+out])
Where R=gas constant =8.3145
T=temperature in kelvin=310.15
So deltaGchem= -5017.69
DeltaGelec=zFdelta membrane potential
=1x 96.5x -53
=-5114.5
Addding these two we get deltag= (-5017.69)+ (-5114.5)x 2
-20264.38
ratio of glucose in to glucose out = e^(delta g / (Fxdelta cell potential))