Question

Why does the enzyme trypsin get deactivated when introduced in the gastric juice of the stomach?

- The optimum pH for trypsin is about 8.0, which is the pH of the intestine, whereas the pH of gastric juice is 1.5 - 2.0, which is highly acidic.

- The optimum pH for trypsin is about 2.0, which is the pH of the intestine, whereas the pH of gastric juice is 8.0, which is highly alkaline.

- The optimum temperature for trypsin is about 98.6°F (37°C), which is the temperature of the intestine; whereas the temperature of gastric juice is 392 - 482°F (200°C - 250°C).

Answer 1

The optimum pH for trypsin is about 8.0, which is the pH of the small intestine, whereas the pH of gastric juice is 1.5 - 2.0, which is highly acidic.

Answer 2

The right answer is A.

Trypsin is an endoprotease that hydrolyzes peptide bonds in which a basic amino acid (Lys-Xaa or Arg-Xaa) engages its acidic function (except in the case where the following amino acid (schematized here as "Xaa ") is a Proline). It cuts in C-terminal of these amino acids. In other words, it converts the polypeptide chains into shorter protein chains to allow digestion. Effective at pH 7.5 - 8.5, it is inactivated and digested in a few hours at neutral pH (= 7) in the intestine and at an acidic pH in the stomach.