The various different lipoprotein types in the plasma contain varying amounts of different apoA and apoC subtypes. ApoA and apoC refer to the class of apolipoprotein. Apolipoprotein B-48 (apoB-48) is specific for chylomicrons just as apoB-100 is specific for LDL. Each lipoprotein type, chylomicron, LDL, and HDL, contain apolipoproteins.
#Idl cholesterol free#
Image demonstrates the phospholipid and free cholesterol outer layer with primarily triglycerides and cholesteryl esters internally. Structure of a chylomicron as a representative structure of a typical lipoprotein particle. These lipid-protein complexes vary in their content of lipid and protein. These complexes contain triglyceride lipid droplets and cholesteryl esters surrounded by the polar phospholipids and proteins identified as apolipoproteins. Within the enterocyte the lipids are used for re-synthesis of triglycerides.ĭietary triglyceride and cholesterol, as well as triglyceride and cholesterol synthesized by the liver, are solubilized in lipid-protein complexes. The products of pancreatic lipases then enter the intestinal epithelial cells via the action of various transporters as well as by simple diffusion. Phospholipids are degraded at the sn-2 position by pancreatic PLA 2 releasing a free fatty acid and the lysophospholipid. Pancreatic lipase degrades triglyceride at the sn-1 and sn-3 positions sequentially to generate 1,2-diglycerides and 2-acylglycerols. These lipases, pancreatic lipase and pancreatic phospholipase A 2 (PLA 2) generate free fatty acids and a mixture of mono- and diglycerides from dietary triglycerides. The emulsification of dietary fats renders them accessible to various pancreatic lipases in the small intestine. Some lipid emulsification occurs in the stomach due to the churning action in this organ which renders some of the lipid accessible to gastric lipase. Following the ingestion of food, bile acids are released and secreted into the gut. Bile acids are synthesized from cholesterol in the liver and then stored in the gallbladder. The solubilization (or emulsification) of dietary lipids is accomplished principally in the small intestine by means of the bile acids. Since these molecules are oils, they are essentially insoluble in the aqueous environment of the intestine. The predominant form of dietary lipid in the human diet is triglyceride. In order for the body to make use of dietary lipids, they must first be absorbed from the small intestine.