Question

Short / Long answer type questions.
Describe in proper sequence the digestion of proteins through the various regions of the alimentary canal in humans. How are the end products of protein digestion absorbed into the body?

Answer 1

The different parts of the alimentary canal and the enzymes secreted by them involved in the digestion of proteins can be summarised as:

• In the stomach: Digestion of proteins begins in the stomach. When the food enters the stomach, it mixes with the HCl and the enzyme pepsin secreted by the cells of the stomach that initiate the breakdown of proteins. Pepsin breaks down the peptide bonds.
• In the small intestine: The pancreatic enzymes trypsin, chymotrypsin, and carboxypeptidase break down the polypeptides and result in smaller units called peptides. Intestinal juice released in the small intestine also contains several digestive enzymes (peptidases) that act on the peptide bonds. The end product of protein digestion in the small intestines is amino acids.
• Amino acids, the end product of protein digestion are absorbed by an active absorption process. It occurs either by a carrier transport mechanism (The digested amino acids are carried across the mucosal cell membrane from the intestinal lumen to the cytoplasm of the cell by a carrier system specific to that particular amino acid) or by a glutathione transport system (glutathione is used to transport amino acids).