PROTEINS IN DIET

PROTEINS IN DIET

Foodstuffs containing high protein content are meat, fish, egg and milk. Proteins are also available in wheat, soybeans, oats and various types of pulses.

Proteins present in common foodstuffs are:

1. Wheat: Glutenin and gliadin, which constitute gluten

2. Milk: Casein, lactalbumin, albumin and myosin

3. Egg: Albumin and vitellin

4. Meat: Collagen, albumin and myosin.

Dietary proteins are formed by long chains of amino acids, bound together by peptide linkages.

DIGESTION OF PROTEINS

Enzymes responsible for the digestion of proteins are called proteolytic enzymes.

IN THE MOUTH

Digestion of proteins does not occur in mouth, since saliva does not contain any proteolytic enzymes. So, thedigestion of proteins starts only in stomach

IN THE STOMACH

Pepsin is the only proteolytic enzyme in gastric juice. Rennin is also present in gastric juice. But

it is absent in human.

IN THE SMALL INTESTINE

Most of the proteins are digested in the duodenum and jejunum by the proteolytic enzymes of the pancreatic juice and succus entericus.

Proteolytic Enzymes in Pancreatic Juice

Pancreatic juice contains trypsin, chymotrypsin and carboxypeptidases. Trypsin and chymotrypsin are

called endopeptidases, as these two enzymes break the interior bonds of the protein molecules.

Proteolytic Enzymes in Succus Entericus

Final digestion of proteins is by the proteolytic enzymes present in the succus entericus. It contains dipeptidases, tripeptidases and aminopeptidases.

FINAL PRODUCTS OF PROTEIN DIGESTION

Final products of protein digestion are the amino acids, which are absorbed into blood from intestine.

ABSORPTION OF PROTEINS

Proteins are absorbed in the form of amino acids from small intestine. The levo amino acids are actively

absorbed by means of sodium cotransport, whereas, the dextro amino acids are absorbed by means of

facilitated diffusion. Absorption of amino acids is faster in duodenum and jejunum and slower in ileum.

IN THE STOMACH

Pepsin is the only proteolytic enzyme in gastric juice. Rennin is also present in gastric juice. But

it is absent in human.

IN THE SMALL INTESTINE

Most of the proteins are digested in the duodenum and jejunum by the proteolytic enzymes of the pancreatic juice and succus entericus.

Proteolytic Enzymes in Pancreatic Juice

Pancreatic juice contains trypsin, chymotrypsin and carboxypeptidases. Trypsin and chymotrypsin are

called endopeptidases, as these two enzymes break the interior bonds of the protein molecules.

Proteolytic Enzymes in Succus Entericus

Final digestion of proteins is by the proteolytic enzymes present in the succus entericus. It contains dipeptidases, tripeptidases and aminopeptidases.

FINAL PRODUCTS OF PROTEIN DIGESTION

Final products of protein digestion are the amino acids, which are absorbed into blood from intestine.

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