Explain the reason that the digestive system secretes two different protein enzymes in two different areas of the digestive system

Answer 1

Proteins exhibit tremendous variation in chemical structure and are broken down by several different enzymes. The first class are known as pepsins, which are secreted by the stomach. In the presence of acid (which among other effects, is able to denature proteins, or change the secondary, tertiary, and quaternary structure of proteins) pepsins account for about 10-20 percent of the initial digestion of proteins in the diet. Further down the digestive system, the pancrease secretes a series of more powerful enzymes, trypsins, into the bile via the common bile duct into the duodenum. Protein digestion continues in the duodenum and the jejunum by a process called hydrolysis. The pancreas secretes carboxypeptidases, which further break down proteins into smaller amino acid chains. These 2-3 amino acid chains are absorbed by enterocytes, which line the duodenum and jejunum, and the breakdown into individual amino acids is completed within the enterocytes by peptidases.

So protein breakdown begins in the stomach, continues in the duodenum and jejunum, and is completed at the brush border of the jejunum and within the enterocytes.