Explain the process of protein digestion

Question

What will be an ideal response?

Answer 1

During digestion, proteins are broken down into amino acids with the help of gastric juices, enzymes in the stomach and small intestine, and enzymes from the pancreas and small intestinal lining. A limited supply of amino acids exists in the amino acid pools, which act as a reservoir for protein synthesis. Surplus amino acids are deaminated, with the carbon-containing remnants used for glucose or energy or stored as fat, depending on the body's needs. The nitrogen in the amine groups is eventually converted to the waste product urea and excreted in urine. Nonessential amino acids are synthesized through transamination.
The process of chemical digestion of protein begins in the stomach. Gastrin stimulates the release of HCl from the parietal cells and the inactive enzyme pepsinogen from the chief cells. HCl denatures the protein and converts pepsinogen to pepsin, which breaks polypeptides into shorter chains. Cholecystokinin from the duodenum stimulates release of trypsinogen, carboxypeptidase, and chymotrypsinogen from the pancreas. These proteases hydrolyze the shorter chains into tripeptides and dipeptides. Dipeptidases and tripeptidases hydrolyze the tripeptides and dipeptides into single amino acids that are absorbed through the enterocytes via the portal vein to the liver.