Leaving Certificate Digestion Practice Test

Many digestive enzymes are secreted as inactive precursors to prevent damage to the tissues that produce them. Pepsinogen is such a precursor released by the stomach’s chief cells. In the acidic environment of the stomach, pepsinogen is activated to pepsin by proteolytic cleavage that removes a small activation segment, revealing the active site. Once activated, pepsin begins breaking down proteins in the stomach. This activation is favored by low pH and can be amplified by pepsin’s own activity in a feedback fashion. If pepsinogen were released in its active form, it could start digesting the stomach lining and other proteins too early, which is why the inactive precursor form is used. The other options don’t fit because pepsinogen is not released as digested protein, a free fatty acid, or an active enzyme.