Final answer:
Tagamet and Zantac decrease acid production by binding to H2 receptors on parietal cells.
Step-by-step explanation:
Tagamet (cimetidine) and Zantac (ranitidine) decrease acid production by binding to H2 receptors on parietal cells in the stomach. These medications are part of a class of drugs called H2 blockers, which reduce the amount of acid produced in the stomach. By binding to H2 receptors, they inhibit the action of histamine, a chemical that stimulates acid secretion by parietal cells.