03 Metabolism of Lipids 大学动物营养学课件 英文版.pptVIP

Lipid Metabolism Lipid Transport in Blood Lipids are not water soluble Blood is mainly water… Pack lipids in protein Chylomicrons Made in the enterocytes (small intestine) Lipoproteins(lipids and proteins) VLDL, LDL, HDL made in liver Release of Lipids From Lipoproteins Lipoprotein lipase (LPL) Enzyme anchored on the cell membranes in blood vessels Releases glycerol and free fatty acids from chylomicrons and lipoproteins Glycerol and free fatty acids absorbed by cells Muscle (oxidized as a source of energy) Release of Lipids Chylomicrons ? chylomicron remnants Cholesterol-rich Taken up by liver and fatty acids are metabolized Repackaging in the Liver Lipid is repackaged in the liver to VLDL or very low density lipoprotein Lipoproteins are classified by density Lipoproteins transport lipid to the rest of the body Lipoproteins Classified by density Protein:lipid ratio More protein, increased density More lipid, decreased density Four classes of lipoproteins Chylomicrons VLDL LDL HDL Lipoproteins Differ according to the lipid:protein ratio Density Chylomicrons Very-low–density lipoproteins (VLDL) High lipid content Low-density lipoproteins (LDL) Main cholesterol transport High-density lipoproteins (HDL) Low lipid content Low Density Lipoproteins VLDL ? ? LDL Cholesterol-rich Converted to bile salts Carries cholesterol to tissues Used for membrane synthesis LDL ~ ‘bad cholesterol’ Associated with plaque formation in blood vessels High triglyceride and cholesterol content High Density Lipoproteins Removes cholesterol from: Cells Lipoproteins Deliver cholesterol to liver for excretion Converted to bile salts and excreted in feces HDL ~ ‘good cholesterol’ Is cholesterol ‘bad’ for you? Cell membranes, bile salts, synthesis of steroid hormones Ratio of LDL:HDL vs. total cholesterol Lipid Transport Free fatty acids transported as complex with albumin in blood Lipids rapidly removed from blood Liver Fat depots Other tissue Adipose Tissue Adipocytes are the major stora