DISCUSS THE MAIN STEPS IN TJE DIGESTION OF PROTEIN AS THE FOOD PASSES THROUGH DIFFERENT PARTS OF ALIMENTARY CANAL
The digestion of proteins begins in the stomach and is completed in the small intestine. The digestive juice secreted in the gastric glands present on the stomach walls is called gastric juice. The food that enters the stomach becomes acidic on mixing with this gastric juice.
The main components of gastric juice are hydrochloric acid, pepsinogen, mucus, and rennin. Hydrochloric acid dissolves the bits of food and creates an acidic medium so that pepsinogen is converted into pepsin. Pepsin is a protein- digesting enzyme. It is secreted in its inactive form called pepsinogen, which then gets activated by hydrochloric acid. The activated pepsin then converts proteins into proteases and peptides.
Rennin is a proteolytic enzyme,released in an inactive form called prorennin. Rennin plays an important role in the digestion of milk in children.
The proteins, proteoses and peptides (partially hydrolysed proteins) on reaching the small intestines are acted upon by the proteolytic enzymes of pancreatic juice.
The enzymes of the intestinal juice like dipeptidases now act upon the dipeptides and converts them into absorbable form i.e amino acids.
First of all, the food enters the mouth where no protein digestion takes place as no enzymes for it are present. As the food reaches the stomach, the conditions become higly acidic and the enzymes pepsin and rennin( present only in neonates to digest milk protein caesin) act upon the proteins present in thhe food. But complete digestion of proteins still doesn't occur. The remaining proteins are digested in the Duodenum and the ileum using the pancreatic digestive juices