Ulcer-drug effect on stomach cell. Artwork of an acid-secreting parietal cell from the lining of the human stomach. Large yellow shapes in the cell membrane represent ulcer-healing drugs. At centre is the cell nucleus (purple). Small yellow spheres represent hydrogen ions (protons) produced by the proton pump at centre right. Purple spheres are potassium ions, which drive the pump. The protons secreted by the cell create an acidic pH in the stomach, aiding digestion. The ulcer-healing drugs inhibit the proton pump and thus make the stomach less acidic. Energy-producing mitochondria are green; membranes of the cell's endoplasmic reticulum and golgi bodies are purple and red.