The formation of HCI in the stomach involves the
Select one:
a. active transport of hydrogen ions from parietal cells into the lumen of the stomach.
b. exchange of sodium ions for hydrogen ions in the transport process.
c. active transport of chloride ions from parietal cells into the lumen of the stomach
d. exchange of sodium and bicarbonate ions.
e. the combination of carbon dioxide and water.

HCl is the best-known constituent of gastric juice and is then secreted by the parietal cells. After getting activated, the parietal cells discharge hydrochloric acid into large canaliculi, that is, the deep foldings of the plasma membrane, which continues with the stomach's lumen.

The concentration of hydrogen ions in the secretions of parietal cells is about 3 million times more in comparison to blood, and secretion of chloride takes place against both electric and concentration gradient. Therefore, the tendency of the parietal cell to discharge acid relies upon active transport.