Mechanism of HCl Formation Flashcards
What is the primary site of hydrochloric acid (HCl) formation?
The primary site of HCl formation is the gastric parietal cells in the stomach lining.
What cells in the stomach are responsible for producing HCl?
Parietal cells, also known as oxyntic cells, produce HCl in the stomach.
Describe the mechanism of HCl formation in parietal cells.
HCl formation in parietal cells involves the conversion of carbon dioxide and water into bicarbonate ions and hydrogen ions.
What is the role of carbonic anhydrase in HCl formation?
Carbonic anhydrase is an enzyme that catalyzes the conversion of carbon dioxide and water into bicarbonate ions and hydrogen ions.
How does carbon dioxide (CO2) enter parietal cells for HCl formation?
Carbon dioxide enters parietal cells through diffusion across the cell membrane.
What enzyme converts carbon dioxide and water into bicarbonate ions and hydrogen ions?
Carbonic anhydrase converts carbon dioxide and water into bicarbonate ions and hydrogen ions.
What ion exchanger transports bicarbonate ions out of parietal cells in exchange for chloride ions?
The bicarbonate ions are transported out of parietal cells by a bicarbonate-chloride exchanger, exchanging them for chloride ions.
Describe the role of the hydrogen-potassium ATPase pump in HCl formation.
The hydrogen-potassium ATPase pump, also known as the proton pump, transports hydrogen ions into the stomach lumen in exchange for potassium ions.
Where is the hydrogen-potassium ATPase pump located in parietal cells?
The hydrogen-potassium ATPase pump is located in the apical membrane of parietal cells.
What stimulates the activation of the hydrogen-potassium ATPase pump?
Activation of the hydrogen-potassium ATPase pump is stimulated by histamine, gastrin, and acetylcholine.
How does the hydrogen-potassium ATPase pump contribute to acidification of the stomach lumen?
The hydrogen-potassium ATPase pump acidifies the stomach lumen by pumping hydrogen ions into it, contributing to the formation of gastric acid (HCl).
What is the fate of bicarbonate ions produced during HCl formation?
Bicarbonate ions produced during HCl formation are transported out of parietal cells into the blood, contributing to the alkaline tide.
What is the significance of the chloride shift in HCl formation?
The chloride shift involves the exchange of bicarbonate ions from the blood for chloride ions in parietal cells, maintaining electroneutrality during HCl formation.
Describe the role of histamine in regulating HCl formation.
Histamine is released by enterochromaffin-like (ECL) cells in the stomach lining.
What cells release histamine in the stomach?
Histamine stimulates HCl formation in parietal cells by binding to histamine receptors, activating adenylate cyclase and increasing intracellular cyclic AMP levels.
How does histamine stimulate HCl formation in parietal cells?
Histamine receptors activate the hydrogen-potassium ATPase pump, increasing the secretion of HCl into the stomach lumen.
Explain the role of gastrin in regulating HCl formation.
Gastrin is released by G cells (Gastric cells) in the stomach antrum.
What cells release gastrin in the stomach?
Gastrin stimulates HCl formation in parietal cells by binding to gastrin receptors and increasing intracellular calcium levels.
How does gastrin stimulate HCl formation in parietal cells?
Gastrin receptors activate the hydrogen-potassium ATPase pump, increasing the secretion of HCl into the stomach lumen.
Describe the role of acetylcholine in regulating HCl formation.
Acetylcholine is released by parasympathetic nerve fibers and enteric neurons in the stomach.
What cells release acetylcholine in the stomach?
Acetylcholine stimulates HCl formation in parietal cells by binding to muscarinic receptors and increasing intracellular calcium levels.
How does acetylcholine stimulate HCl formation in parietal cells?
Muscarinic receptors activate the hydrogen-potassium ATPase pump, increasing the secretion of HCl into the stomach lumen.
Explain the regulation of HCl formation by the cephalic phase.
The cephalic phase of HCl formation is triggered by the sight, smell, taste, or thought of food.
What triggers the cephalic phase of HCl formation?
The cephalic phase stimulates the release of acetylcholine, gastrin, and histamine, leading to HCl formation in parietal cells.
