Mechanism of HCl Formation

Question 1

What is the primary site of hydrochloric acid (HCl) formation?

Answer 1

The primary site of HCl formation is the gastric parietal cells in the stomach lining.

Question 2

What cells in the stomach are responsible for producing HCl?

Answer 2

Parietal cells, also known as oxyntic cells, produce HCl in the stomach.

Question 3

Describe the mechanism of HCl formation in parietal cells.

Answer 3

HCl formation in parietal cells involves the conversion of carbon dioxide and water into bicarbonate ions and hydrogen ions.

Question 4

What is the role of carbonic anhydrase in HCl formation?

Answer 4

Carbonic anhydrase is an enzyme that catalyzes the conversion of carbon dioxide and water into bicarbonate ions and hydrogen ions.

Question 5

How does carbon dioxide (CO2) enter parietal cells for HCl formation?

Answer 5

Carbon dioxide enters parietal cells through diffusion across the cell membrane.

Question 6

What enzyme converts carbon dioxide and water into bicarbonate ions and hydrogen ions?

Answer 6

Carbonic anhydrase converts carbon dioxide and water into bicarbonate ions and hydrogen ions.

Question 7

What ion exchanger transports bicarbonate ions out of parietal cells in exchange for chloride ions?

Answer 7

The bicarbonate ions are transported out of parietal cells by a bicarbonate-chloride exchanger, exchanging them for chloride ions.

Question 8

Describe the role of the hydrogen-potassium ATPase pump in HCl formation.

Answer 8

The hydrogen-potassium ATPase pump, also known as the proton pump, transports hydrogen ions into the stomach lumen in exchange for potassium ions.

Question 9

Where is the hydrogen-potassium ATPase pump located in parietal cells?

Answer 9

The hydrogen-potassium ATPase pump is located in the apical membrane of parietal cells.

Question 10

What stimulates the activation of the hydrogen-potassium ATPase pump?

Answer 10

Activation of the hydrogen-potassium ATPase pump is stimulated by histamine, gastrin, and acetylcholine.

Question 11

How does the hydrogen-potassium ATPase pump contribute to acidification of the stomach lumen?

Answer 11

The hydrogen-potassium ATPase pump acidifies the stomach lumen by pumping hydrogen ions into it, contributing to the formation of gastric acid (HCl).

Question 12

What is the fate of bicarbonate ions produced during HCl formation?

Answer 12

Bicarbonate ions produced during HCl formation are transported out of parietal cells into the blood, contributing to the alkaline tide.

Question 13

What is the significance of the chloride shift in HCl formation?

Answer 13

The chloride shift involves the exchange of bicarbonate ions from the blood for chloride ions in parietal cells, maintaining electroneutrality during HCl formation.

Question 14

Describe the role of histamine in regulating HCl formation.

Answer 14

Histamine is released by enterochromaffin-like (ECL) cells in the stomach lining.

Question 15

What cells release histamine in the stomach?

Answer 15

Histamine stimulates HCl formation in parietal cells by binding to histamine receptors, activating adenylate cyclase and increasing intracellular cyclic AMP levels.

Question 16

How does histamine stimulate HCl formation in parietal cells?

Answer 16

Histamine receptors activate the hydrogen-potassium ATPase pump, increasing the secretion of HCl into the stomach lumen.

Question 17

Explain the role of gastrin in regulating HCl formation.

Answer 17

Gastrin is released by G cells (Gastric cells) in the stomach antrum.

Question 18

What cells release gastrin in the stomach?

Answer 18

Gastrin stimulates HCl formation in parietal cells by binding to gastrin receptors and increasing intracellular calcium levels.

Question 19

How does gastrin stimulate HCl formation in parietal cells?

Answer 19

Gastrin receptors activate the hydrogen-potassium ATPase pump, increasing the secretion of HCl into the stomach lumen.

Question 20

Describe the role of acetylcholine in regulating HCl formation.

Answer 20

Acetylcholine is released by parasympathetic nerve fibers and enteric neurons in the stomach.

Question 21

What cells release acetylcholine in the stomach?

Answer 21

Acetylcholine stimulates HCl formation in parietal cells by binding to muscarinic receptors and increasing intracellular calcium levels.

Question 22

How does acetylcholine stimulate HCl formation in parietal cells?

Answer 22

Muscarinic receptors activate the hydrogen-potassium ATPase pump, increasing the secretion of HCl into the stomach lumen.

Question 23

Explain the regulation of HCl formation by the cephalic phase.

Answer 23

The cephalic phase of HCl formation is triggered by the sight, smell, taste, or thought of food.

Question 24

What triggers the cephalic phase of HCl formation?

Answer 24

The cephalic phase stimulates the release of acetylcholine, gastrin, and histamine, leading to HCl formation in parietal cells.

Question 25

Describe the regulation of HCl formation by the gastric phase.

Answer 25

The gastric phase of HCl formation is triggered by the presence of food in the stomach.

Question 26

What triggers the gastric phase of HCl formation?

Answer 26

The gastric phase stimulates the release of gastrin and histamine, further enhancing HCl formation in parietal cells.

Question 27

Explain the regulation of HCl formation by the intestinal phase.

Answer 27

The intestinal phase of HCl formation is triggered by the entry of partially digested food into the duodenum.

Question 28

What triggers the intestinal phase of HCl formation?

Answer 28

The intestinal phase inhibits gastrin release and decreases histamine action, reducing HCl formation in parietal cells.

Question 29

Describe the role of somatostatin in inhibiting HCl formation.

Answer 29

Somatostatin is released by D cells (Delta cells) in the stomach lining.

Question 30

What cells release somatostatin in the stomach?

Answer 30

Somatostatin inhibits HCl formation by suppressing the release of gastrin, histamine, and acetylcholine, reducing the activity of parietal cells.