Final answer:
The major digestive zymogens released from the pancreas include trypsinogen, chymotrypsinogen, and procarboxypeptidase. They are converted into their active forms, trypsin, chymotrypsin, and carboxypeptidase respectively, inside the small intestine.
Step-by-step explanation:
The pancreas plays a crucial role in the digestive process by releasing various zymogens or inactive forms of enzymes. These zymogens, which are inactive to prevent the pancreas from digesting itself, require activation in the duodenum to carry out their function. The major pancreatic zymogens discussed include trypsinogen, chymotrypsinogen, and procarboxypeptidase.
Activation of Pancreatic Zymogens
Once inside the small intestine, trypsinogen is converted into its active form, trypsin, by enteropeptidase, which is an enzyme secreted by the intestinal mucosal cells. Trypsin then activates other zymogens such as chymotrypsinogen into chymotrypsin. This enzyme now actively breaks down proteins, focusing on peptide bonds involving carboxyl groups of aromatic amino acids. Similarly, procarboxypeptidase is cleaved by trypsin to form carboxypeptidase, which hydrolyzes peptide linkages at the free carboxyl end of peptide chains.
The pancreas also secretes other digestive enzymes in their active forms, such as pancreatic amylase, pancreatic lipase, and pancreatic nuclease, because they don't attack the pancreas like protein-digesting enzymes do. Pancreatic amylase breaks down starch into simpler carbohydrates but cannot cleave α-1→6 glycosidic linkages found at the branching points of starch and glycogen. These are instead digested by isomaltase or α-dextrinase. The pancreatic lipase is responsible for lipid digestion, and pancreatic nuclease assists in the breakdown of nucleic acids.
Lastly, the pancreatic juices are also rich in bicarbonate, which serves to neutralize the acidic chyme entering the small intestine from the stomach, creating an optimal environment for the proper functioning of these digestive enzymes.