Protein, Lipid and Carbohydrate Digestion Essay Example | Topics and Well Written Essays - 500 words

Protein, Lipid and Carbohydrate Digestion - Essay Example It is inside the stomach, where is it temporarily stored, that preliminary chemical digestion begins. Partially digested food then goes to the small intestine where much of the digestion and absorption of nutrients occur. The large intestine simply serves for the further absorption of water. Chemical digestion of proteins starts in the stomach. The stomach produces HCl which converts pepsinogen to pepsin. Pepsin is a kind of endopeptidase which splits the internal peptide bonds in the protein molecules. That is, it breaks the primary structure of the protein. As opposed to endopeptidases, exopeptidases split the first or last peptide bond in the polypeptide. Zymogens, a form of protease, are secreted by the pancreas, which in turn are activated by enteropeptidase. Enteropeptidases convert trypsinogen to trypsin, which then hastens the conversion of more trypsinogen to trypsin. Furthermore, other zymogens are converted by trypsin into their active forms. Carboxypeptidase is converted from procarboxypeptidase. Chymotrypsin is converted from chymotrypsinogen. Both trypsin and chymotrypsin are endopeptidases. Carboxypeptidase, on the other hand, is an exopeptidase. Protein digestion is a concerted effort of all these enzymes. Lipid or fat digestion occurs only in the small intestine. As a result, most fat/lipid molecules remain undigested when they reach the duodenum.