<prompt> The pump responsible for gastric acid secretion isH ATPaseNa - H ATPaseH - K ATPaseCa2 - H ATPase  <response>: Gastric parietal cells are highly specialized for their unusual task of secreting concentrated acid. The cells are packed with mitochondria that supply energy to drive the apical H,K-ATPase, or proton pump, that moves H ions out of the parietal cell against a concentration gradient. The apical membrane also contains potassium channels, which supply the K ions to be exchanged for H, and Cl- channels that supply the counterion for HCl secretion. 