Protein Digestion and Absorption

The human body relies heavily on proteins. Muscles, eyes, hair, organs, enzymes and hormones are all made up of proteins. Our body also depends on proteins for repair and maintenance. People can make their bodies consume protein more effectively by ensuring that their protein is of the best quality.

Protein 

Proteins are the building blocks of life. Fish, seafood, milk, yogurt, and beans are some protein-rich foods. Consumption of proteins is essential for repairing and building new cells and maintaining and improving muscle strength. During protein digestion and absorption, the body must break down protein to absorb it and use it effectively for body processes. Certain conditions, such as aging and strenuous exercise, can increase a person’s protein requirement.

Protein Digestion and Absorption 

Acids and enzymes in the stomach interact to digest protein. Proteins are broken down by the enzymes activated by the stomach acid. 

• In the first place, pepsin, an enzyme in the stomach, breaks down and splits the proteins in the food into shorter polypeptides.
• The pancreas further releases enzymes into the small intestine, where the polypeptide chains are broken, and breaking down peptides and amino acids begins.
• The small intestine releases more peptidases to digest the food by breaking down the proteins into amino acids.
• Finally, the amino acids are carried across the small intestinal wall and into the bloodstream. They are taken up and utilized by the tissues in the body to maintain normal, healthy functioning.

Digestion of proteins

• Consuming protein in the diet provides amino acids used to make cellular substances.
• A protein’s absorption requires it to be broken down into amino acids. Dipeptides, tripeptides, and amino acids are digested products of protein.
• A peptide-degrading enzyme called endopeptidase hydrolyzes the interior peptide bonds of proteins, while an exopeptidase enzyme hydrolyzes one amino acid at a time from the C-terminus of proteins.
• The small intestine and the stomach are involved in indigestion.

The enzymes involved are:

Pepsin

• The chief cells of the stomach secrete pepsin in its zymogen form as pepsinogen.
• Gastric H+ triggers the conversion of pepsinogen into pepsin. A pH of 1- 3 is ideal for pepsin.  
• Proteins are hydrolyzed by pepsin into peptides and proteoses.
• Pepsin denatures when the pH exceeds 5. HCO3 thereby increases pH in the duodenum and inactivates pepsin in the intestines as the pancreas secretes it.

Pancreatic proteases

• With the action of the pancreatic and intestinal juice, the digestion is completed in the small intestine.
• Among the proteases are trypsin, elastase, chymotrypsin, carboxypeptidase A, and carboxypeptidase B.
• Inactive forms of these enzymes are secreted into the small intestine, which activates them as follows:
  • By using enterokinase, trypsinogen is converted to trypsin.
  • The enzyme trypsin converts the inactive forms of proelastase, chymotrypsinogen and procarboxypeptidase A and B into their active forms.

Absorption of Proteins

The absorption of proteins occurs in the small intestine, with various enzymes acting upon them.

1. Free amino acids

• In the luminal membrane, co-transport of Na+ dependent amino acids takes place. Glucose and galactose co-transporters are analogous to this transporter.
• The facilitated diffusion transports amino acids from the cells to the blood.
• Four different carriers exist for neutral, acidic, basic, and amino acids.

2. Dipeptides and tripeptides

As compared to free amino acids, they are absorbed faster.

The luminal membrane is also capable of transporting dipeptides and tripeptides.

 The cytoplasmic peptidases hydrolyze the dipeptides and tripeptides into amino acids after being transported into intestinal cells.

The facilitated diffusion transports the amino acids from the cells to the blood.

Conclusion :

The body depends on protein for nearly every function. Before the amino acids are released into the bloodstream, they are digested in the mouth, stomach and small intestine. By eating complete proteins and by chewing thoroughly before swallowing, you can maximize your intake of nutrients from protein sources. Our bodies have a more challenging time absorbing protein in our older years. Athletes require a higher amount of protein to maintain their muscle health. Eating a healthy diet can improve our bodies’ ability to absorb protein, but a diet alone may not be enough. You would need a balanced diet to absorb proteins in the body.