4. What part of the gastrointestinal tract contains trypsin? Explain your answer with reference to the data.

Trypsin is found in the **small intestine**, specifically the **duodenum**.While trypsin is *produced* by the pancreas in an inactive form called trypsinogen, it isn't activated until it reaches the duodenum. The duodenum is the first section of the small intestine, where the partially digested food from the stomach mixes with pancreatic juices. Within these pancreatic juices are several enzymes, including trypsinogen. Trypsinogen is then activated into trypsin by an enzyme called enteropeptidase, which is secreted by the cells lining the duodenum. Therefore, although the *origin* of trypsin is the pancreas, the *active* form of the enzyme carries out its function of protein digestion in the duodenum of the small intestine.