Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 8

The Case of the Acid Stomach. The gastric juice in your stomach has a pH of 2.0. This acidity is due to the secretion of protons into the stomach by the epithelial cells of the gastric mucosa. Epithelial cells have an internal pH of 7.0 and a membrane potential of -70 mV (inside is negative)and function at body temperature (37°C).
(a)What is the concentration gradient of protons across the epithelial membrane
(b)Calculate the free energy change associated with the secretion of 1 mole of protons into gastric juice at 37°C.
(c)Do you think that proton transport can be driven by ATP hydrolysis at the ratio of one molecule of ATP per proton transported
(d)If protons were free to move back into the cell, calculate the membrane potential that would be required to prevent them from doing so.