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Q69 - Localizing Drug Targets in the Parietal Cell Acid-Secretion Pathway

Theoretical B Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Digestive & Metabolic Physiology

Figure Q.69 shows the regulation of HCl secretion in the parietal cell of the stomach.

Figure Q.69

Drugs 1, 2, 3, and 4 inhibit gastric acid secretion differently in vivo via one of the four pathways: inactivating the H+/K+ ATPase, blocking the Histamine 2 receptor, blocking Gastrin receptor, and blocking Acetylcholine (Ach) receptor.

A set of experiments were conducted to determine in which pathway these drugs inhibit gastric acid secretion. Parietal cells were isolated and cultured in different media. Each medium contained one of the four drugs. Each drug-containing medium was added with one of three compounds (Histamine, Gastrin, Ach). The HCl secretion of parietal cells in the cultures was determined. The following table shows the results of the experiments (-: no HCl secretion; +: HCl secretion; ?: not shown).

No drug Drug 1 Drug 2 Drug 3 Drug 4
No addition - - - - -
Histamine added ? ? ? ? -
Gastrin added ? ? ? + ?
Ach added + - ? ? -

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. HCl was secreted by the parietal cells cultured in the medium containing Drug 1 and Histamine.
B. Drug 2 blocked Gastrin receptors.
C. Drug 3 blocked Histamine 2 receptors.
D. The parietal cells cultured in the medium containing Drug 4 and Ach had lower levels of intracellular K+ than the cells cultured in the medium containing only Ach.
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Question reproduced from IBO 2016, Theoretical Paper B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)