Explain the digestion and absorption of proteins in human intestine.

Explanation

Digestion of proteins begin in the stomach
1. The gastric juice contains HCl and proenzymes.
2. The proenzyme pepsinogen on exposure to HCI gets converted into the active enzyme pepsin which converts proteins into proteoses and pepatones (Peptides).
3. Rennin is a proteolytic enzymes found in the gastric juice of infants . It helps in digestion of milk protein caseinogen to casein in the presence of calcium ions.
Digestion in small Intestine :
1. The bile. pancreatic juice and intestinal juice are the secretions released into the small intestine.
2. The pancreatic juice contains enzymes such as trypsinogen, chymotrypsinogen and carboxy peptidases for digestion of proteins. Bile plays no role in protein digestion.
Trypsinogen (Inactive) `overset(Enterokinase (intestinal mucosa))to` Typsin (Active)
Chymotrypsinogen (Inactive) overset(Trypsin) to Chymotrypsin (Active)`
Proteins and partially digested proteins in the chyme are acted upon by proteolytic enzymes of pancreatic juice.
Trypsin hydrolyses proteins into polypeptides and peptones.
Chymotrypsin hydrolyses peptide bonds associated with specific aminoacids.
The enzymes in the intestinal juice (succus entericus) such as dipeptidases act on the end products of pancreatic digestion of proteins.
Dipeptides, Tripeptides `overset(Peptidase) to` Aminoacids
As a result of digestion, proteins are converted into their respective monomeric units.
`Proteins to Amino acids
The simple substances are absorbed in the jejunum and ileum region of the small intestine.
Absorption :
1. The villi in the lumen of ileum are the absorbing units which are supplied with blood capillaries .
2. Small amounts , of amino acids are generally absorbed by simple diffusion .
3. Nutrients like amino acids are absorbed into the blood against the concentration gradient by active transport .
4. Absorbed substances are transported through blood to the like through the hepatic portal system .
5. From the liver , nutrients are transported to all other regions of the body for utilization.
6. All the body tissues utilize the absorbed substance for their activities and incorporate into their protoplasm . This process is called assimilation .