Lipid Metabolism - Lipid Metabolism Subject Lehninger...

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Lipid Metabolism Lehninger Principles of Biochemistry, 5th Edition Subject Chapter Reading Lipid Structure & Chemistry (Review) 10 pp 343-350, 355,359 Lipid Degradation 17 pp 647-665 Ketogenesis 17 pp 666-668 Fatty acid Synthesis 21 pp 805-817 Integration 23 various Triglyceride/Phospholipid Biosynthesis 21 pp 820-831 Cholesterol/Steroid metabolism/ 21 pp 831-845 Lipoproteins
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Lipid Classes (Review) 1. Simple fatty acids - saturated -unsaturated 2. Mono, di- and triglyceride 3. Glycerolphospholipids (phosphoglycerides) e.g. lecithin (phosphatidyl choline) 4. Sphingolipids 5. Steroids 6. Prostaglandins 7. Lipid Vitamins
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Lipid Catabolism Triglyceride Glycerol + Fatty Acids Glycolysis Sat Unsat Odd Fatty Acids ACETYL-CoA Propionyl- CoA Succinyl-CoA TCA HMG CoA Ketone Bodies CO 2 ACETYL-CoA
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Lipid Anabolism(Biosynthesis) Fatty acids Cholesterol ACETYL-CoA Prostaglandins Phospholipids Triglycerides Sphingolipids HMG-CoA Steroids Bile Acids Vit D
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General Triglyceride Catabolism - Fatty acids in triglycerides (TG) are the major source of energy in the body. TG are stored in adipocytes or are found in dietary fat. - 40% of daily energy requirement of people in industrial countries is met with TG. - Main tissues using fatty acids as energy source are liver, heart and resting skeletal muscle - A 70kg male has about 7 kg of lipid. A 65 kg female has about 14 kg of lipid. This is adequate for about a month of starvation.
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-There are carbohydrate stores for only about a day -Carbohydrate and protein yield about 4 kcal energy/g, whereas, triglycerides yield about 9 kcal of energy/g - Excess dietary carbohydrate is converted into TG - Two reasons for using fat as an energy storage form are its high energy yield/g and since fat is very hydrophobic, it can be stored in a compact form.
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Utilization of Dietary Fats Bile salts and pancreatic lipases in the small intestines lead to breakdown of dietary fats to fatty acids, glycerol, mono- and diglycerides for absorption into the intestine. These absorbed products are used to re- synthesize triglycerides (TG) in the intestinal cells and the TG are then distributed to various tissues in the body by lipoproteins.
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Mobilization of Fats in Adipocytes (Fat Cells) -Within the fat cells in peripheral tissues, lipids are stored in oil drops. -When needed, the triglycerides are broken down by a different lipase called the hormone sensitive lipase . triacylglycerides glycerol fatty acids lipase CH 2 O CH 2 O O H 2 OH 2 OH HO H + H 2 O + RCO 2 _ RCO 2 _ RCO 2 _ R O R O R O
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Hormone Sensitive Lipase Lehn fig 17-3 Hydrolyzes triglycerides to glycerol and free fatty acids Hormonally regulated Provides mechanism of liberating stored fatty acids so they can be distributed to other tissues. Albumin carries fatty acids in bloodstream
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Regulation of Hormone Sensitive Lipase Epinephrine or Glucagon Insulin stimulates adenylyl cyclase cyclic AMP stimulates protein kinase inactive protein active protein kinase A kinase A ATP ADP inactive lipase mobilized & active lipase- P TG glycerol + fatty acids -
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Glycerol Metabolism CH 2 OH CH 2 OH HO H + ATP CH 2 OPO 3 _ CH 2 OH HO H + ADP CH 2
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Lipid Metabolism - Lipid Metabolism Subject Lehninger...

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