Re: Candida

 I've expalined some of the basics, here is an advanced explanation:

http://en.wikipedia.org/wiki/Stomach_acid

Gastric acid secretion happens in several steps. Chloride and hydrogen ions are secreted separately from the cytoplasm of parietal cells and mixed in the canaliculi. Gastric acid is then secreted into the lumen of the oxyntic gland and gradually reaches the main stomach lumen.

Chloride and sodium ions are secreted actively from the cytoplasm of the parietal cell into the lumen of the canaliculus. This creates a negative potentialof -40 mV to -70 mV across the parietal cell membrane that causes potassium ions and a small number of sodium ions to diffuse from the cytoplasm into the parietal cell canaliculi.

The enzyme carbonic anhydrase catalyses the reaction between carbon dioxide and water to form carbonic acid. This acid immediately dissociates into hydrogen and bicarbonate ions. The hydrogen ions leave the cell through H⁺/K⁺ ATPase antiporter pumps.

At the same time sodium ions are actively reabsorbed. This means the majority of secreted K⁺ and Na⁺ ions return to the cytoplasm. In the canaliculus, secreted hydrogen and chloride ions mix and are secreted into the lumen of the oxyntic gland.

The highest concentration that gastric acid reaches in the stomach is 160 mM in the canaliculi. This is about 3 million times that of arterialblood, but almost exactly isotonic with other bodily fluids. The lowest pH of the secreted acid is 0.8,^[1] but the acid is diluted in the stomach lumen to a pH between 1 and 3.