Calculate the free energy change of pumping Ca⁺² from the cytosol, where its concentration is about 1.0 x 10^-7 M, to the extracellular fluid, where its concentration is about 1.0 mM. Assume a temperature of 37^oC and a transmembrane potential of 50 mV (inside more negative) for the plasma membrane.

Calculate the maximum [Glucose]in/[Glucose]out 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^oC.