Q.12:- Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal.
The digestion of protein starts in stomach and completes in small intestine.
In stomach, active pepsin is formed by the action of HCl on inactive pepsinogen converts proteins into proteases and peptones.
In small intestine, the pancreatic juice contains inactive enzymes – trypsinogen, chymotrypsinogen and procarboxypeptidases in the inactive form. Trypsinogen is activated by an enzyme, enterokinase, secreted by the intestinal mucosa into active trypsin, which in turn activates the other enzymes in the pancreatic juice. Chymotrypsinogen and procarboxypeptidases get converted into chymotrypsin and carboxypeptidase in the presence of trypsin. Chymotrypsin converts the proteins into peptides, and carboxypeptidase further converts peptides into smaller peptide chains and amino acids.