NURSING EXAM QUESTIONS
BIOCHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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It is denatured in the alkaline pH of the small intestine.
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It is used up by proteins in the stomach.
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It is inhibited by the alkalinity of stomach pH
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It is replaced by proteins in the stomach
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Detailed explanation-1: -Pepsin will continue to work at the same rate as it moves through the intestines until all the protein is broken down. Salivary amylase activates pepsin, converting it to a functioning form in the stomach. Pepsin will cease to function in the small intestine as basic secretions from the pancreas neutralize the pH.
Detailed explanation-2: -Answer and Explanation: Pepsin would not function in the small intestine because it requires an acidic environment to optimally work for protein digestion. Similarly, trypsin would not work in the stomach as acids will convert it into its inactive form.
Detailed explanation-3: -The digestive power of pepsin is greatest at the acidity of normal gastric juice (pH 1.5–2.5). In the intestine the gastric acids are neutralized (pH 7), and pepsin is no longer effective.
Detailed explanation-4: -Pepsin is a stomach enzyme that serves to digest proteins found in ingested food. 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-5: -Pepsin cleaves peptide bonds in the amino-terminal side of the cyclic amino acid residues (tyrosine, phenylalanine, and tryptophan), breaking the polypeptide chains into smaller peptides (Fange and Grove, 1979).