Lecture 10 Lipid Metabolism

Lecture 10 Lipid Metabolism - IPHY 3060 Lecture 10: Lipid...

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Unformatted text preview: IPHY 3060 Lecture 10: Lipid Metabolism Key Point from Last Time: Fatty acids can be oxidized to produce ATP via the Citric Acid Cycle How do cells obtain lipids for use as an energy substrate? Cells Obtain Lipids 2 Different Ways: Synthesizing lipids themselves Importing them from the blood after they are digested and absorbed by the intestines most important Import of Lipids from the Blood Lipid Transport Proteins Because lipids are insoluble in aqueous solutions like blood plasma, lipids need to be transported by proteins in the blood and extracellular fluid Lipid Transport Proteins Albumin Lipoproteins Lipoprotein complexes Composed of proteins and lipids Forms a spherical particle with a polar surface and a non- polar core 4 Main Classes of Lipoprotein Complexes Chylomicronscarry triglycerides from intestines to liver and other tissues VLDLcarry triglycerides from liver to tissues LDLcarry lipids and cholesterol to liver and to tissues HDLdelivers cholesterol from tissues to liver for disposal Lipoprotein delivery of lipids SR-BI Steps of lipid delivery by lipoproteins Dietary lipids are absorbed by intestinal cells, which package them into chylomicrons Chylomicrons are delivered to and taken up by the liver The liver releases repackaged lipids as VLDL particles VLDL particles are converted to LDL particles by lipoprotein lipase (LPL) found on the surface of blood vessel cells LDL can be taken up by the liver or by other cells in the body Excess cholesterol is packaged into HDL and returns to the liver for excretion 2 Main Pathways for Importing Lipids Into Cells from Lipoproteins Extracellular hydrolysis of lipoprotein lipids followed by transport-protein-mediated uptake by cells Lipoprotein-mediated endocytosis Transport protein-mediated lipid import Lipids are cleaved from lipoprotein complexes extracellularly by lipoprotein lipase Lipids are then imported into the cell by transport proteins Plasma membrane lipids can move from transporter into plasma membrane Other lipids are bound by intracellular binding proteins LPL Lipoprotein-mediated endocytosis Lipoprotein binds to cell surface receptor Lipoprotein-mediated endocytosis Lipoprotein binds to cell surface receptor Lipoprotein binding causes internalization by receptor- mediated endocytosis Lipoprotein-mediated endocytosis Lipoprotein binds to cell surface receptor Lipoprotein binding causes internalization by receptor- mediated endocytosis Low pH in endosome causes lipoprotein complex to detach from receptor Lipoprotein-mediated endocytosis Lipoprotein binds to cell surface receptor Lipoprotein binding causes internalization by receptor- mediated endocytosis Low pH in endosome causes lipoprotein complex to detach from receptor Receptor vesicles split off and are recycled back to the cell membrane Lipoprotein-mediated endocytosis...
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Lecture 10 Lipid Metabolism - IPHY 3060 Lecture 10: Lipid...

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