Gastric acid network (called canaliculi) from which the hydrochloric acid is secreted into the lumen of the stomach. The pH of gastric acid is 1.5 to 3.5 in the human stomach lumen, the acidity being maintained by the proton pump H/K ATPase. The parietal cell releases bicarbonate into the bloodstream in the process, which causes a temporary rise of pH in the blood, known as an alkaline tide. The highly acidic environment in the stomach lumen causes proteins from food to lose their characteristic folded structure (or denature). This exposes the protein's peptide bonds. The gastric chief cells of the stomach secrete
Break key scancodes at all on release; therefore it is not possible for any software to determine whether this key is being held down. On modern keyboards, the key is usually labeled "Pause" with "Break" below, sometimes separated by a line: formula_1, or "Pause" on the top of the keycap and "Break" on the front. In most Windows environments, the key combination brings up the system properties. Compact and notebook keyboards often do not have a dedicated key. These may use the following substitutes for : Substitutes for : Apple keyboards do not have the Pause/Break key, as Mac OS X does