Question

Compose an essay tracing the path of proteins nutrients throughout each part of the gastrointestinal tract and give an account of what would happen in each one of them. Provide as many details as possible to come up with a thorough picture of the destiny of proteins in the human body.

Answer 1

Destiny of proteins in Human body:

• Proteins nutrients taken as food follows the path of gastrointestinal tract starting with ingesting it from buccal cavity to the area where completely digested proteins gets absorbed. The whole process is the part of digestion takes place with the help of various digestive juices containing enzymes for digestion.
• No protein is digested in the buccal cavity as the saliva does not contain any protein digesting enzyme. Proteins are only digestible with the help of enzymes present in gastric juice of stomach, pancreatic juice and intestinal juice present in intestine.
• Gastric juice contains two proenzymes: propepsin and prorenin. Propepsin enzyme is converted into pepsin by HCl which convert the protein into peptides in an acidic medium. Prorenin is converted into renin by HCl which covert the soluble milk protein (casein) into insoluble compound called paracasein which is further coverted into peptides by pepsin.
• From the stomach, food reaches into the intestine where it is mixed with the pancreatic juice and intestinal juice, and intestinal juice show its action which digests the protein in an alkaline medium created by the bile juice.
• Pancreatic juice contains 2 proenzymes - trypsinogen and chymotrypsinogen and 1 enzyme - carboxypolypeptidases. Trypsinogen is converted into trypsin by a non-digestive enzyme enterokinase which digests the protein into peptide. Chymotrypsinogen is converted into chymotrypsin by trypsin which converts the protein into peptides. Then, carboxypolypeptidases hydrolyse the last peptide bond of the polypeptide chain to release its last aminoacid thereby changing the polypeptides into dipeptide or peptide.
• Intestinal juice contains aminopeptidases and dipeptidases which completes the digestion of protein by converting the dipeptides into amino acids. Finally, from the site of large intestine, absorption of aminoacids into the bloodstream takes place.