Question

All of the enzymes that digest protein are

a. secreted by the pancreas
b. secreted by the liver
c. stimulated by enterokinase
d. secreted in an inactive form

Answer 1

Protein-digesting enzymes are secreted by the pancreas in inactive forms to prevent self-digestion. The small intestine, particularly the duodenum, is where these enzymes, such as trypsinogen, are activated by enteropeptidase. Other enzymes like amylase and lipase are secreted in their active forms as they do not attack the pancreas.

Step-by-step explanation:

The pancreas is responsible for producing protein-digesting enzymes. However, to prevent self-digestion, these enzymes are secreted in their inactive forms, known as proenzymes. Once they reach the small intestine, specifically the duodenum, they are activated. An important enzyme in this activation process is enterokinase (also called enteropeptidase), which is produced by the intestinal mucosa. Enterokinase converts trypsinogen (an inactive enzyme from the pancreas) into its active form, trypsin. Trypsin then further activates other proenzymes like procarboxypeptidase and chymotrypsinogen into their active forms—carboxypeptidase and chymotrypsin—leading to protein digestion.

Enzymes that digest starch (amylase), fat (lipase), and nucleic acids (nuclease) are secreted by the pancreas in their active forms because they do not pose the same risk of attacking the pancreas as do the protein-digesting enzymes.