Cells in the wall of the mammalian stomach secrete HCl at a concentration of 0.15 M. The secreted protons, which are derived from the intracellular hydration of CO2 by carbonic anhydrase, are pumped out by an (H+ -K+)-ATPase antiport. A K+- Cl co-transporter is also required to complete the overall transport process.
(a) Calculate the pH of the secreted HCl. How does this compare to the cytosolic pH (7.4)?
(b) Write the reaction catalyzed by carbonic anhydrase.
(c) Draw a diagram to show how the action of both transport proteins results in the secretion of HCl.