In the situations described below, what is the free energy change if 1 mole of Na* is transported across a membrane from a region where the concentra- tion is 1 µM to a region where it is 100 mM? (Assume T = 37 °C.) (a) In the absence of a membrane potential. (b) When the transport is opposed by a membrane potential of 70 mV. (c) In cach case, will hydrolysis of 1 mole of ATP suffice to drive the trans- port of 1 mole of ion, assuming pH 7.4 and the following cytoplamic concentrations: ATP= 4.60 mM, P = 5.10 mM, ADP = 310 µM?

Calculate the maximum ratio that can be achieved by the plasma membrane Na+-glucose symporter of an epithelial cell when [Na+]in is 12 mM, [Na+]out is 145 mM, the membrane potential is −50 mV (inside negative), and the temperature is 37 °C.

shown below, which of the following would likely happen if the glucose facilitated diffusion transporter, typically located on the basal side of epithelial cells, was also located in the apical side. [Glucose] low Glu Na [Na] high Lumen of kidney or intestine Apical membrane Epithelial cell [Glucose] high Glu Na* [Na] low Glucose would be actively transported into the lumen of the organ. Glucose concentration would be higher in the lumen of the organ and lower in the cytosol of the epithelial cells. O More glucose would be transported in the extracellular fluid. O The sodium/potassium ATPase would stop working.

Determine whether you would expect the interior of an H+transport protein to be positively or negatively charged. Briefly explain your reasoning.