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 CH 2 OH CH 2 OH HO H + H 2 O + RCO 2 _ RCO 2 _ RCO 2 _ R