Explain the physiology of protein digestion in a human body .

Explanation

Digestion in Stomach`:`
Gastric juice `:` Pepsin, and Renin are the proteases present in gastric juice
(i) Pepsin `:` It is an enzyme produced in an inactive form called pepsinogen. Pepsinogen is activated by HCl. Pepsin is an endopeptidase and it breaks inner peptide bonds of the protein molecule to form proteoses, peptones, and polypeptides.
Proteins ` underset("pH 1.5 to 2.5 ")overset("Pepsin")(rarr)` Proteoses, Peptones & Polypeptides.
(ii) Renin `:` Renin is also secreted in an inactive form called prorenin. It is activated by HCl. Renin acts on the milk protein called casein, and converts it into paracasein. Paracasein in turn combines with calcium salts, and forms calcium paracaseinate ( curdy precipitate ).
Casein `underset("pH 1.5 to 2.5")overset("Renin")(rarr)` Paracasein
Paracasein `+` Calcium `underset("pH 1.5 to 2.5")overset("Renin")(rarr)` Calcium paracaseinate ( curdy ppt. )
This process of conversion into calcium paracaseinate is called curdling of milk.
Pancreatic juice `:` Trypsin, Chymotrypsin and Carboxypeptdase are the proteases secreted by the pancreas.
(i) Trypsin `:` It is secreted as an inactive trypsinogen. Later gets activated by enterokinase of the intestinal juice. Trypsin is a endopeptidase. It acts on proteins and converts them into Proteoses, Peptones and Polypeptides.
Proteins `underset("pH 7.1 to 8.2")overset("Trypsin")(rarr)` proteoses, Peptones and Polypeptides
(ii) Chymotrypsin `:` It is secreted as an inactive chymotrypsin and later gets activated by trypsin. Chymotrypsin is also an endopeptidase and convertes Protein into Polypeptides.
Protein `underset("pH 7.1 to 8.2")overset("Chymotrypsin")(rarr)` Polypeptides.
(iii) Carboxypeptidase `:` It converts polypeptides into Tripeptides, Dipeptides and Amino acids.
Polypeptides `underset("pH 7.1 to 8.2")overset("Carboxypeptidase")(rarr)` Tripeptides , Dipeptides, Amino acids.
Intestinal juice `:` The four proteases forming the intenstinal juice are Aminopeptidase. Dipeptidase,Tripeptidase and Erepsin.
(i) Aminopeptidase `:` It is a exopeptidase which acts on the terminal ends of the polypeptides and convert them into Tripeptides, Dipeptides and Amino acids.
Polypeptides `underset("pH 7.1 to 8.2")overset("Aminopeptidase")(rarr)` Tripeptides, Dipeptides, Amino acids.
(ii) Tripeptidase `:` It acts on the Tripeptide units and converts them into amino acids.
Tripeptide `underset("pH 7.1 to 8.2")overset("Tripeptidase")(rarr)` Amino acids
(iii) Dipeptidase `:` It acts on Dipeptide untis and converts them into Amino acids.
Depeptide `underset("pH 7.1 to 8.2")overset("Dipeptidase")(rarr)` Amino acids.
(iv) Erepsin `:` It is a powerful protease of the intestine. it converts polypeptides, and other short chain Amino acids into free Amino acids.
Polypeptide `underset("pH 7.1 to 8.2")overset("Erepsin")(rarr)` Amino acids