posted by Sasha .
Explanation of the digestion of protein in the human body.
Cheif cells in the stomach secrete pepsinogen, the zymogen precursor to pepsin. The pH of the stomach activates pepsin and also plays a role in the breakdown of proteins by causing denaturation. Large proteins are broken down to smaller proteins by pepsin, and are moved to the small intestine to be broken down into di and tri-peptides. The pancreas secretes trypsin and chymotrypsin, which facilitates the breakdown of proteins even further; enterokinase activates trypsin and trypsin activates chymotrypsin to break down peptides into di and tri-peptides. The di and tri-peptides are shuttled to the brush-border where brush-border enzymes called peptidases break down di and tri-peptides into individual amnio acids where they are absorbed so they can be used by cells to construct proteins, or to be used as an energy source.