Digestion And Absorption

Pancreatic juice reaches the duodenum carrying several proenzymes, including the inactive trypsinogen, kept inactive to protect the pancreas from self-digestion. NCERT Class 11, Chapter 16 (Digestion and Absorption) states that the intestinal mucosal enzyme enterokinase (enteropeptidase) converts trypsinogen into the active protease trypsin. Once formed, trypsin then activates further trypsinogen as well as the other pancreatic proenzymes chymotrypsinogen and procarboxypeptidase, creating an amplifying activation cascade. Hydrochloric acid is wrong because, although HCl activates gastric pepsinogen into pepsin, it acts in the stomach and is neutralised in the alkaline duodenum, so it cannot activate trypsinogen there. Bile salts are incorrect since their role is the physical emulsification of fats, with no involvement in proenzyme activation. Salivary amylase is a carbohydrate-digesting enzyme acting on starch in the mouth and has no protease-activating ability whatsoever. The correct trigger is therefore enterokinase. This arrangement also has a protective logic: keeping the activator confined to the intestinal lining ensures the powerful proteases are switched on only after they have safely left the pancreatic tissue, guarding the gland against autodigestion. A mechanistic plausibility check reinforces this: because trypsin sits at the head of the pancreatic protease cascade, it requires a separate, locally produced activator, and enterokinase from the intestinal lining precisely fulfils that role.