Lipoproteins Lecture 27 PDF

LIPOPROTEINS Lipoproteins Clusters of proteins and lipids. Function in transporting lipids in the blood. All lipoproteins contain: Core of neutral lipids (cholesteryl ester and triacylglycerols) 2 Surface coat: polar lipids(free cholesterol and phospholipids) 3 Apolipoproteins. I.. - Classified as 1...

LIPOPROTEINS Lipoproteins Clusters of proteins and lipids. Function in transporting lipids in the blood. All lipoproteins contain: Core of neutral lipids (cholesteryl ester and triacylglycerols) 2 Surface coat: polar lipids(free cholesterol and phospholipids) 3 Apolipoproteins. I.. - Classified as 1. Size - ester and has triglyceride it density-depends phospholipid the more more the more of the 2. on how cholesterol bigger trig and the size cholesterol of on. lipoprotein these the dense the lipoprotein Lipoproteins Loading… biggest in cholestrol & size becoming smaller memorize this HDL LDL VLDL II Cholesteryl ester II Cholesteryl ester Apolipoproteins Lipid-binding proteins that function in lipid transport. Loading… Apolipoproteins acts as: Structural components of lipoprotein particles, Cofactors for enzymes and Ligands for cell-surface receptors. Classes of apolipoproteins: Divided into 5 major classes Function not fully understood (A , B , < , D , E) Chylomicrons Metabolism Responsible for carrying dietary triglycerides and cholesteryl ester from enterocytes to the blood and finally to the liver. Chylomicrons are formed in enterocytes with apo-48, released in lymphatic system and in blood. ApoCII (lipoprotein lipase activator) and ApoE are added to “nascent” [incomplete] chylomicron. Both the apolipoproteins come from HDL TAGs breaks to free fatty acids which enter adipose tissue and glycerol goes to liver. The small chylomicrons(remnants) with only cholesteryl ester and some TAGs enter liver. VLDL Metabolism Begins in the liver, consist of mostly triglycerides and some cholesteryl ester synthesized in the liver VLDL has Apo B-100 on it and it is released in the blood. Apo CII [lipoprotein lipase activation] and Apo E are added(given by HDL) In the circulation: TAG is degraded by lipoprotein lipase VLDL decreases in size converting to IDL ApoC II and ApoE return to HDL VLDL converts to LDL via formation of IDL. LDL Metabolism LDL particles are made from degradation of VLDL via formation of IDL. LDL largely contains cholesteryl ester and very small amount of triglycerides along with Apo B 100 LDL particles expressing Apo B100 bind to negatively-charged LDL receptors which are coated HDL Structure HDL: Smallest and most dense lipoprotein Structure of HDL: Synthesized in the liver as discoid shape containing phosphatidylcholine (lecithin) and ApoA-I, ApoC-II, and ApoE changes into sphere when cholesterol is added on it by extrahepatic tissues. HDL particles remove fats and cholesterol, from cells, and within artery wall and transport it back to the liver for excretion or re-utilization i.e. why it is called as “good cholesterol” Reverse cholesterol transport (i.e. from the extrahepatic cells Cholesterol is going back to liver) In the liver, cholesterol: Changes to bile Is disposed via bile. Transported to steroidogenic cells for hormone synthesis