Acid production in the stomach MCQs With Answer

by

Acid production in the stomach MCQs With Answer

Understanding stomach acid production is essential for B. Pharm students studying pharmacology, gastroenterology, and drug design. This introduction covers gastric acid secretion mechanisms, parietal cell physiology, key regulators like gastrin, histamine (H2), and acetylcholine (M3), and clinical relevance including H. pylori, NSAID-related mucosal injury, and therapies such as proton pump inhibitors (PPIs), H2 blockers, antacids, and mucosal protectants. Learn molecular targets like the H+/K+ ATPase, carbonic anhydrase, and CYP-mediated PPI metabolism to optimize treatment strategies and anticipate drug interactions and adverse effects. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which acid is primarily secreted by parietal cells in the stomach?

  • Hydrochloric acid (HCl)
  • Carbonic acid (H2CO3)
  • Acetic acid
  • Sulfuric acid

Correct Answer: Hydrochloric acid (HCl)

Q2. Parietal cells that secrete gastric acid are predominantly located in which region of the stomach?

  • Antrum
  • Fundus and body (oxyntic mucosa)
  • Pylorus
  • Cardia

Correct Answer: Fundus and body (oxyntic mucosa)

Q3. Which enzyme in parietal cells catalyzes the formation of H+ and HCO3- required for acid secretion?

  • Pepsin
  • Carbonic anhydrase
  • ATP synthase
  • Aminopeptidase

Correct Answer: Carbonic anhydrase

Q4. The final step in gastric acid secretion is mediated by which membrane protein?

  • Na+/K+ ATPase
  • H+/K+ ATPase (proton pump)
  • V-type H+ ATPase
  • Cl-/HCO3- exchanger

Correct Answer: H+/K+ ATPase (proton pump)

Q5. Among primary agonists, which is considered the most potent stimulator of parietal cell acid secretion?

  • Acetylcholine
  • Histamine acting on H2 receptors
  • Somatostatin
  • Secretin

Correct Answer: Histamine acting on H2 receptors

Q6. Histamine stimulates acid secretion through which intracellular messenger in parietal cells?

  • cGMP
  • cAMP
  • Inositol triphosphate (IP3)
  • Nitric oxide

Correct Answer: cAMP

Q7. Gastrin, an important stimulant of acid secretion, is secreted by which gastric cells?

  • Chief cells
  • G cells in the antrum
  • Parietal cells
  • Enterochromaffin-like (ECL) cells

Correct Answer: G cells in the antrum

Q8. Which peptide hormone directly inhibits gastric acid secretion?

  • Gastrin
  • Somatostatin
  • Histamine
  • Cholecystokinin (CCK)

Correct Answer: Somatostatin

Q9. Vagal stimulation increases acid secretion primarily via which receptor on parietal cells?

  • Beta-1 adrenergic receptor
  • M3 muscarinic receptor
  • H1 histamine receptor
  • CCK-B receptor

Correct Answer: M3 muscarinic receptor

Q10. K+ recycling at the apical membrane of parietal cells is essential because:

  • K+ is the main secreted ion in gastric juice
  • K+ is required for H+/K+ ATPase function to exchange intracellular H+ for luminal K+
  • K+ neutralizes HCl in lumen
  • K+ stimulates gastrin release

Correct Answer: K+ is required for H+/K+ ATPase function to exchange intracellular H+ for luminal K+

Q11. Proton pump inhibitors (PPIs) require which condition for activation to their active sulfenamide form?

  • Neutral pH of the stomach
  • Acidic canalicular environment of parietal cells
  • Presence of bile salts
  • Presence of pepsin

Correct Answer: Acidic canalicular environment of parietal cells

Q12. Which statement about PPIs is correct?

  • PPIs are active drugs at neutral pH and inhibit H2 receptors
  • PPIs are prodrugs that irreversibly inhibit H+/K+ ATPase after activation in acidic environment
  • PPIs directly neutralize gastric acid
  • PPIs increase gastrin degradation

Correct Answer: PPIs are prodrugs that irreversibly inhibit H+/K+ ATPase after activation in acidic environment

Q13. Why are many PPIs formulated as enteric-coated tablets?

  • To enhance absorption in the stomach
  • To prevent acid-mediated degradation before reaching small intestine for absorption
  • To deliver drug directly to colon
  • To increase taste masking

Correct Answer: To prevent acid-mediated degradation before reaching small intestine for absorption

Q14. A recognized long-term adverse effect associated with chronic PPI therapy is:

  • Hypomagnesemia
  • Hyperkalemia
  • Pancreatitis
  • Pulmonary fibrosis

Correct Answer: Hypomagnesemia

Q15. Which of the following is a commonly used H2 receptor antagonist?

  • Omeprazole
  • Misoprostol
  • Famotidine
  • Sucralfate

Correct Answer: Famotidine

Q16. The primary mechanism of action of antacid medications is:

  • Irreversible inhibition of H+/K+ ATPase
  • Neutralization of gastric acid to raise lumen pH
  • Blocking H2 receptors on parietal cells
  • Stimulating mucus production via prostaglandins

Correct Answer: Neutralization of gastric acid to raise lumen pH

Q17. The gold-standard noninvasive test to monitor intragastric acidity over 24 hours is:

  • Serum gastrin measurement
  • 24-hour esophageal pH probe (ambulatory pH monitoring)
  • Upper GI endoscopy alone
  • Stool occult blood test

Correct Answer: 24-hour esophageal pH probe (ambulatory pH monitoring)

Q18. Helicobacter pylori survives gastric acidity primarily by producing which enzyme?

  • Urease
  • Peptidase
  • Lipase
  • Protease

Correct Answer: Urease

Q19. Chronic H. pylori infection most commonly leads to which gastric condition?

  • Gastric achlorhydria without inflammation
  • Chronic gastritis and increased risk of peptic ulcer disease
  • Duodenal atresia
  • Immediate gastric perforation in all cases

Correct Answer: Chronic gastritis and increased risk of peptic ulcer disease

Q20. Zollinger-Ellison syndrome causes acid hypersecretion due to a tumor that secretes:

  • Histamine
  • Gastrin (gastrinoma)
  • Somatostatin
  • Ach receptor agonists

Correct Answer: Gastrin (gastrinoma)

Q21. Proton pump inhibitors inhibit acid secretion by which mode of inhibition?

  • Competitive reversible inhibition of H2 receptors
  • Irreversible covalent inhibition of H+/K+ ATPase
  • Blocking muscarinic receptors reversibly
  • Neutralizing gastric lumen pH

Correct Answer: Irreversible covalent inhibition of H+/K+ ATPase

Q22. Which drug is a prostaglandin analogue used to prevent NSAID-induced gastric ulcers?

  • Misoprostol
  • Omeprazole
  • Ranitidine
  • Sucralfate

Correct Answer: Misoprostol

Q23. NSAIDs promote gastric mucosal injury primarily by:

  • Stimulating gastrin secretion
  • Inhibiting cyclooxygenase and reducing protective prostaglandins
  • Activating H+/K+ ATPase directly
  • Increasing HCl synthesis in parietal cells

Correct Answer: Inhibiting cyclooxygenase and reducing protective prostaglandins

Q24. Sucralfate protects ulcerated mucosa by:

  • Neutralizing stomach acid like antacids
  • Forming a viscous, adhesive barrier over ulcers
  • Blocking histamine H2 receptors
  • Inhibiting gastrin secretion

Correct Answer: Forming a viscous, adhesive barrier over ulcers

Q25. The bicarbonate secreted by surface epithelial cells contributes to mucosal defense by:

  • Enhancing pepsin activity
  • Neutralizing acid at the epithelial surface forming a pH gradient
  • Stimulating parietal cell acid secretion
  • Inhibiting mucus secretion

Correct Answer: Neutralizing acid at the epithelial surface forming a pH gradient

Q26. Which basolateral exchanger helps supply chloride for gastric acid secretion?

  • Na+/K+ ATPase on apical membrane
  • Cl-/HCO3- exchanger (anion exchanger)
  • Glucose transporter
  • Ca2+/Na+ exchanger

Correct Answer: Cl-/HCO3- exchanger (anion exchanger)

Q27. Which H2 antagonist is well known for antiandrogenic side effects like gynecomastia?

  • Famotidine
  • Cimetidine
  • Nizatidine
  • Ranitidine

Correct Answer: Cimetidine

Q28. Omeprazole can reduce the effectiveness of clopidogrel because both drugs interact via:

  • Renal excretion pathways
  • CYP2C19-mediated metabolism
  • Plasma protein binding displacement
  • Direct antagonism at P2Y12 receptor

Correct Answer: CYP2C19-mediated metabolism

Q29. Gastrin stimulates acid secretion indirectly by acting on which cells to release histamine?

  • Parietal cells directly only
  • Enterochromaffin-like (ECL) cells
  • Chief cells
  • Goblet cells

Correct Answer: Enterochromaffin-like (ECL) cells

Q30. The H+/K+ ATPase is localized on which membrane domain of the parietal cell?

  • Basolateral membrane facing blood
  • Apical/canalicular membrane facing gastric lumen
  • Mitochondrial membrane
  • Endoplasmic reticulum membrane

Correct Answer: Apical/canalicular membrane facing gastric lumen

Q31. During which phase of digestion is gastric acid secretion maximal?

  • Cephalic phase (sight/smell of food)
  • Gastric phase (food in stomach)
  • Intestinal phase (food in intestine)
  • Fasting state

Correct Answer: Gastric phase (food in stomach)

Q32. A reliable noninvasive diagnostic test for active H. pylori infection is the:

  • Urea breath test
  • Serum pepsinogen level
  • Fasting gastrin assay
  • Complete blood count

Correct Answer: Urea breath test

Q33. Gastrin binds to which receptor on parietal and ECL cells?

  • H2 histamine receptor
  • CCK-B (CCK2) receptor
  • M3 muscarinic receptor
  • V2 vasopressin receptor

Correct Answer: CCK-B (CCK2) receptor

Q34. Which of the following is a potassium-competitive acid blocker (P-CAB) used as an alternative to PPIs?

  • Omeprazole
  • Vonoprazan
  • Famotidine
  • Sucralfate

Correct Answer: Vonoprazan

Q35. Gastric prostaglandins protect the mucosa by all EXCEPT:

  • Stimulating mucus and bicarbonate secretion
  • Maintaining mucosal blood flow
  • Stimulating acid secretion via H+/K+ ATPase
  • Promoting epithelial cell restitution

Correct Answer: Stimulating acid secretion via H+/K+ ATPase

Q36. Which H2 receptor antagonist has the highest potency per mg for suppressing acid?

  • Ranitidine
  • Cimetidine
  • Famotidine
  • Nizatidine

Correct Answer: Famotidine

Q37. Activation of H2 receptors on parietal cells increases which intracellular second messenger to enhance acid secretion?

  • Calcium via IP3/DAG pathway
  • cAMP via adenylate cyclase
  • cGMP via guanylate cyclase
  • ATP via direct synthesis

Correct Answer: cAMP via adenylate cyclase

Q38. Maximal antisecretory effect of once-daily PPI therapy is generally achieved after:

  • One single dose
  • 3–4 days of consistent dosing
  • 4–6 weeks only
  • Immediate intravenous administration

Correct Answer: 3–4 days of consistent dosing

Q39. Which antacid ingredient commonly causes constipation as a side effect?

  • Magnesium hydroxide
  • Aluminum hydroxide
  • Calcium carbonate
  • Sodium bicarbonate

Correct Answer: Aluminum hydroxide

Q40. The chloride ion in gastric juice is supplied to the lumen primarily by which process?

  • Passive diffusion through tight junctions only
  • Transport through apical chloride channels following basolateral Cl-/HCO3- exchange
  • Direct secretion by chief cells
  • Endocytosis of plasma chloride

Correct Answer: Transport through apical chloride channels following basolateral Cl-/HCO3- exchange

Q41. The H+/K+ ATPase exchanges intracellular H+ for extracellular K+ using energy from:

  • GTP hydrolysis
  • ATP hydrolysis
  • Passive diffusion gradients
  • Sodium motive force

Correct Answer: ATP hydrolysis

Q42. Inhibition of carbonic anhydrase in parietal cells would be expected to:

  • Increase gastric acid secretion
  • Decrease gastric acid secretion
  • Have no effect on acid secretion
  • Directly block H2 receptors

Correct Answer: Decrease gastric acid secretion

Q43. Which hormone released from the duodenum in response to acid inhibits gastric emptying and reduces acid secretion?

  • Gastrin
  • Secretin
  • Histamine
  • Ghrelin

Correct Answer: Secretin

Q44. A standard first-line triple therapy for H. pylori eradication commonly includes:

  • PPI, clarithromycin, and amoxicillin
  • H2 blocker, metronidazole, and bismuth
  • Antacid alone for 14 days
  • Misoprostol and sucralfate

Correct Answer: PPI, clarithromycin, and amoxicillin

Q45. Which clinical syndrome is characterized by recurrent peptic ulcers and markedly increased gastric acid secretion?

  • Achalasia
  • Zollinger-Ellison syndrome
  • Crohn’s disease
  • Peptic ulcer disease due to H. pylori only

Correct Answer: Zollinger-Ellison syndrome

Q46. The postprandial “acid pocket” refers to:

  • A localized zone of unbuffered acid near the gastroesophageal junction after a meal contributing to reflux
  • An acid-free area in the stomach after eating
  • A region of high bicarbonate secretion
  • A duodenal area of low acidity

Correct Answer: A localized zone of unbuffered acid near the gastroesophageal junction after a meal contributing to reflux

Q47. A finding consistent with hypochlorhydria on gastric testing would be:

  • Elevated basal acid output (BAO)
  • Low basal acid output and high gastric pH
  • High pepsin activity
  • Markedly low serum bicarbonate only

Correct Answer: Low basal acid output and high gastric pH

Q48. Which luminal stimuli are most effective at stimulating gastrin release and therefore acid secretion?

  • Carbohydrates only
  • Amino acids and peptides from protein digestion
  • Lipids primarily
  • Simple sugars like glucose exclusively

Correct Answer: Amino acids and peptides from protein digestion

Q49. Intrinsic factor, necessary for vitamin B12 absorption, is secreted by which stomach cell?

  • Chief cell
  • Parietal cell
  • Mucous neck cell
  • Enterochromaffin-like cell

Correct Answer: Parietal cell

Q50. Long-term suppression of gastric acid with PPIs can predispose patients to which infectious complication?

  • Increased risk of Clostridioides difficile infection and small intestinal bacterial overgrowth
  • Immediate viral gastroenteritis only
  • Decreased risk of all enteric infections
  • Lower respiratory tract sterilization

Correct Answer: Increased risk of Clostridioides difficile infection and small intestinal bacterial overgrowth

Leave a Comment