Enzymes and Digestion of Carbs, Proteins, Fats · Physiology

Pepsinogen is the inactive zymogen secreted by gastric chief cells. What is the primary mechanism for its conversion into the active enzyme pepsin?

  1. Cleavage by enterokinase in the duodenum
  2. Cleavage by trypsin in the gastric lumen
  3. Spontaneous acid-catalyzed cleavage at pH below 5
  4. Activation by gastrin-binding in the gastric pits
Show answer and explanation

Correct answer: Spontaneous acid-catalyzed cleavage at pH below 5

In the presence of hydrochloric acid (pH < 5), pepsinogen undergoes a conformational change that allows it to cleave itself (autocatalysis) to form active pepsin. Once some pepsin is formed, it further accelerates the activation of more pepsinogen.

Difficulty: Medium Question 24 of 40

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