胆汁（bile）.ppt

Remember Miller Experiment? TCA Makes pancreatic juices and hormones Pancreas 胰脏 Function The pancreas is both an exocrine and endocrine gland. The exocrine portion of the gland produces a secretion that contains enzymes that are capable of hydrolyzing proteins, fats, and carbohydrates The endocrine portion of the gland, the pancreatic islet, produces the hormones insulin and glucagon that play a key role in carbohydrate metabolism Pancreatic juice is clear, colorless and watery solution; pH is slightly basic 8.0-8.3 Contains 1.5% solids 2/3 of solids : inorganic matter 1/3 of solids : organic matter Pancreatic juice HCO3: content is very high ( 5 times more than the plasma). Cl Na K small amounts of Phosphate, Ca, Mg inorganic matter Organic matter: enzymes/proenzymes Enzymes are produced, stored and released as their inactive precursors so that they don’t digest and destroy the pancreas itself. Main pancreatic enzyme : protease trypsin chymotrypsin elastase Carboxypeptidase pancreatic lipase Amylase Inactive : trypsinogen. Activated by enteropeptidase ( 肠激酶）. Properties : Trypsin (胰蛋白酶) Alkaline pH 8.0-9.0 Endopeptidase Activates other pancreatic proenzyme is active against the peptide bonds in protein molecules that have carboxyl groups donated by Arg and Lys Trypsin inhibitor is present in the pancreatic juice as well as in the plasma Chymotrypsin (胰凝乳蛋白酶) secreted in the inactive form. Activated by trypsin. Endopeptidase pH 8-9 is active against the peptide bonds in protein molecules that have carboxyl groups donated by Tyr,Phe,Trp,Met and Leu Pancreatic lipase It is water soluble and can act only on the surface of fat globules after their emulsification. Acts only in the presence of bile salts which seems to activate it. Activity is increased by certain proteins and amino acids. Optimum pH is 8.2- 9.2. ?Zymogen Activation by Proteolytic Cleavage secrtin (促胰液素） cholecystokinin (CCK, 胆囊收缩素) Regu