Chapter24

Chapter24 - BCH 4054 Chapter 24 Lecture Notes Slide 1...

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Chapter 24, page 1 BCH 4054 Chapter 24 Lecture Notes Slide 1 Chapter 24 Fatty Acid Catabolism Slide 2 Fatty Acids as Energy Source • Triglycerides yield 37 kJ/g dry weight • Protein 17 kJ/g • Glycogen 16 kJ/g (even less wet weight) • Total stored energy in body (Table 24.1) • Fat ~555,000 kJ • Protein ~ 102,000 kJ • Glycogen ~ 3,000 kJ • More reduced than carbohydrate Slide 3 Fatty Acids as Energy Source, con’t. • Major Sources of Fatty Acids • Stored Fat (Adipose Tissue) • Dietary Fat • Biosynthetic Fat (from glucose in liver) • Low solubility of Triglyceride and Fatty Acids require special transport mechanisms involving lipoproteins
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Chapter 24, page 2 Slide 4 Adipose Tissue Triglycerides • Triglycerides hydrolyzed by hormone sensitive lipase • Hormonal (epinephrine, glucagon, ACTH) stimulation activates the cyclic AMP pathway • Fatty acids and glycerol released to the blood • Fatty acids bound to serum albumin for transport in blood • See Fig 24.2 Binding to serum albumin helps to minimize the detergent properties of fatty acids, which otherwise might be strong enough to disrupt cellular membranes. Slide 5 Dietary Triglycerides • Mixed with bile salts to form micelles • Hydrolyzed in the duodenum by pancreatic lipase to fatty acids plus monoglycerides • Micelles adsorbed into epithelial cells where triglycerides are resynthesized and packaged into chylomicrons, which are released into the lymphatic system, then the blood • Short chain fatty acids are transported directly to the portal vein. (See Fig 24.3 and 24.4) Slide 6 Biosynthetic Triglycerides • Made in the liver from carbohydrate • Exported as part of a lipoprotein called very low density lipoprotein (VLDL) • (VLDL is discussed in Section 25.5, page 840) • Triglycerides from both VLDL and chylomicrons are hydrolyzed in the blood by lipoprotein lipase, releasing free fatty acids (FFA) to tissues Lipoprotein lipase is attached to the surface of blood vessels in tissues. The attachment can be released by administration of heparin.
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Chapter 24, page 3 Slide 7 Fatty Acid Activation • Once fatty acids get into the cell, they are immediately activated to thiol esters of coenzyme A. • This costs the equivalent of 2 ATP (Fig 24.7) • Oxidation occurs in the mitochondria, but CoASH esters cannot cross the mitochondrial membrane Slide 8 Role of Carnitine in Fatty Acid Oxidation • To cross the mitochondrial membrane, fatty acids are transesterified to form esters of the amino
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Chapter24 - BCH 4054 Chapter 24 Lecture Notes Slide 1...

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