[Campbell Biology P.969] If you put the following events in the order they occur in the huma... | Practice Question

If you put the following events in the order they occur in the human digestive system, which would be the third event in the series?

  • A: Cells in gastric pits secrete protons.
  • B: Pepsin activates pepsinogen.
  • C: HCl activates pepsinogen.
  • D: Partially digested food enters the small intestine.

Explanation

The logical sequence of these events in the human digestive system is: 1. Cells in gastric pits secrete protons and chloride . 2. HCl is formed and activates pepsinogen into pepsin. 3. Pepsin then autocatalytically activates more pepsinogen. Therefore, 'Pepsin activates pepsinogen' is the third event.