Hydrochloric acid, also called HCl, is a clear, highly corrosive liquid. HCl is one of the many chemicals released in our stomach when we eat a meal. The role of hydrochloric acid in the stomach, along with the other gastric juices, is to break down foods and cause the release of enzymes that further aid digestion. HCl also protects the body from illness by killing pathogens commonly found on foods.
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Hydrochloric acid is naturally found in the gastric juices of the stomach. The gastric juices, together referred to as gastric acid, contain mostly potassium chloride, or KCl, and sodium chloride, or NaCl. As hydrochloric acid is such a strongly corrosive chemical, it only makes up around 5 percent of the composition of gastric acid. This gives gastric acid a very low pH range, usually between 1 to 2.
Hydrochloric acid is secreted through the parietal cells of the stomach. However, before HCl can be secreted and start digesting food, a few other things must happen. Peptides, found primarily in protein, stimulate the process that leads to HCl secretion. Peptides cause a chemical called gastrin to be secreted by G-cells. The presence of gastrin then stimulates the release of histamine. Finally, the histamine stimulates the parietal cells to begin secreting HCl.
HCl Digestion of Foods
Because of its highly acidic properties, HCl is able to dissolve many of the foods we eat. The corrosiveness of HCl also aids in fighting off infections and helping the immune system. HCl kills any pathogens, disease-causing particles or organisms that may be on the foods we eat. HCl is so strong that if it wasn't for the mucous membrane that protects the stomach lining, the acid would digest the stomach.
HCl and Enzyme Activation
HCl also has another important role to play in the stomach during the digestion process. The presence of HCl in the body of the stomach causes the activation of enzymes. One of the proteins in HCl is used to convert the enzyme pepsinogen into pepsin. Pepsin breaks up the peptides from the protein.
- "Handbook of Physiology"; Cell Biology of Hydrochloric Acid Secretion; John G. Forte, Andrew Soll; 1989
- "Annuals of New York Academy of Science" Pumps and pathways for gastric HCl secretion; Forte et al.; 1989
- "Krause's Food and Nutrition Therapy"; Escott-Stump and Mahan; 2007