PHYSIOLOGY
GASTROINTESTINAL PHYSIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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pH
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From the amount of gastric mucosa
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presence of water
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None of the above
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Detailed explanation-1: -Gastric chief cells secrete pepsin as an inactive zymogen called pepsinogen. Parietal cells within the stomach lining secrete hydrochloric acid that lowers the pH of the stomach. A low pH (1.5 to 2) activates pepsin.
Detailed explanation-2: -Secreted pepsinogen has an N-terminal peptide of 44 amino acids blocking the active site. On exposure to pH values below 5, carboxyl groups become protonated abolishing charge–charge interactions. This allows part of the N-terminal protein into the active site where it is cleaved, releasing a 16-amino acid peptide.
Detailed explanation-3: -Answer and Explanation: High pH indicates an alkaline environment which stabilizes the proenzyme pepsinogen and as such, remains inactive.