[Campbell Biology P.957] Which of the following correctly describes a step in protein digest... | Practice Question

Which of the following correctly describes a step in protein digestion, including the enzyme and its product s ?

  • A: Proteins in the stomach are broken down by trypsin into smaller polypeptides.
  • B: Small polypeptides in the small intestine are acted upon by pancreatic carboxypeptidase to yield amino acids.
  • C: Small peptides are acted upon by dipeptidases, carboxypeptidase, and aminopeptidase (from intestinal epithelium) to produce amino acids.
  • D: Pancreatic trypsin and chymotrypsin convert proteins directly into small peptides.

Explanation

According to Figure 41.11, Dipeptidases, carboxypeptidase, and aminopeptidase, which are enzymes from the intestinal epithelium, act on small peptides derived from protein breakdown by pancreatic enzymes to yield the final absorbable products, amino acids. Option A is incorrect because pepsin, not trypsin, is the stomach enzyme. Option B is incorrect because pancreatic carboxypeptidase yields small peptides, not directly amino acids. Option D is incorrect because pancreatic trypsin and chymotrypsin act on smaller polypeptides from the stomach, producing smaller polypeptides, not directly converting proteins to small peptides.