Pepsin and Trypsin are protein digesting enzymes. Their optimum pH values are 2 and 9.5 respectively. What is the location of these enzymes in the digestive tract?

Pepsin is a protein-digesting enzyme secreted by the gastric glands of the stomach. It requires a highly acidic medium for its activation and optimal activity, which is provided by hydrochloric acid (HCl) in the stomach, maintaining a pH of around $1.8$ to $2.0$.

Trypsin is secreted as inactive trypsinogen by the pancreas into the duodenum (the first part of the small intestine). It is activated by enterokinase and operates optimally in an alkaline medium with a pH of around $7.8$ to $9.5$, which is maintained by bicarbonate ions in the pancreatic juice and bile.

Therefore, the location of Pepsin is the stomach and Trypsin is the duodenum.

Answer: Pepsin: Stomach : Trypsin : Duodenum.