How HCl is made in the Stomach

[NerdFencer]

This is the answer to the question posed in class today. The website
below explains the process in better detail, but I will copy the
essentials from the page below.

* Hydrogen ions are generated within the parietal cell from
dissociation of water. The hydroxyl ions formed in this process
rapidly combine with carbon dioxide to form bicarbonate ion, a
reaction cataylzed by carbonic anhydrase.
* Bicarbonate is transported out of the basolateral membrane in
exchange for chloride. The outflow of bicarbonate into blood results
in a slight elevation of blood pH known as the "alkaline tide". This
process serves to maintain intracellular pH in the parietal cell.
* Chloride and potassium ions are transported into the lumen of
the cannaliculus by conductance channels, and such is necessary for
secretion of acid.
* Hydrogen ion is pumped out of the cell, into the lumen, in
exchange for potassium through the action of the proton pump;
potassium is thus effectively recycled.
* Accumulation of osmotically-active hydrogen ion in the
cannaliculus generates an osmotic gradient across the membrane that
results in outward diffusion of water - the resulting gastric juice is
155 mM HCl and 15 mM KCl with a small amount of NaCl.

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/stomach/parietal.html