Proton Pump HCl — FRCA Primary MCQ
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Correct answer: A — H+/K+ ATPase
The H+/K+ ATPase (proton pump) on the apical membrane secretes H+ in exchange for K+. It generates an H+ gradient of approximately 3 million to 1. PPIs (omeprazole) irreversibly inhibit this pump. H2 receptor antagonists (ranitidine) reduce acid secretion by blocking histamine-stimulated parietal cell activity.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist