BCH-8 Lipid Metabolism

BCH-8 Lipid Metabolism - LIPID METABOLISM Stored lipids are...

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LIPID METABOLISM Stored lipids are a great source of energy; these are mostly triacylglycerols stored in adipose tissue . Catabolism of stored fats is carried out in mitochondria, after hydrolysis of triacylglycerols by lipase, the long chain fatty acids are fed by β - oxidation as acetyl-CoA units shuttled into the citric acid cycle. Lipids are synthesized in the cytosol of the cell using NADPH , whereas the catabolism of lipids occurs in the mitochondria using FAD and NAD + .
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How are Lipids Catabolized? – Both triacylglycerols and phosphoacylglycerols can be hydrolyzed to release fatty acids. Lipases and phospholipases release the fatty acids. Phospholipases can hydrolyze the molecule in four places and yield slightly different products. hospholipases re active ingredients of pider and Phospholipases are active ingredients of spider and snake venoms . Hormones control the release of fatty acids from adipose tissue. The binding of epinephrine activates adenylate cyclase which leads to active protein kinase A which phosphorylates triacylglycerol lipase.
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Phospholipase A 2 – from the pancreas, heart, snake venoms (rattlesnake and cobra) Phospholipase C – bacteria Clostridium perfringens and Bacillus cereus Phospholipase D – peanuts, cabbage and bacteria Streptomyces
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Fatty Acid Oxidation – Begins with activation of the molecule, a thioester bond is formed between the carboxyl group of the fatty acid and the thiol group of coenzyme A (CoA-SH). The enzyme that carries out this reaction, acyl-CoA synthetase requires ATP for action. The fatty acid is adenylated by ATP, then the thioester is formed with hydrolysis of the pyrophosphate supplying energy.
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Esterification takes place in the cytosol, and the acyl-CoA can cross the outer mitochondrial membrane, but not the inner membrane. The acyl group is transferred to carnitine by transesterification by carnitine palmitoyltranferase ( CPT-I ) with specificity for acyl groups with 14-18 carbons. The acylcarnitine is transported through the inner membrane by carnitine translocase . The acylcarnitine in converted back to acyl-CoA by carnitine palmitoyltranferase ( CPT-II ), completing a shuttling system to get the acyl-CoA from the cytosol to the mitochondrial matrix.
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β -oxidation , a repeated sequence of reactions successively cleaves two-carbon units from the
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BCH-8 Lipid Metabolism - LIPID METABOLISM Stored lipids are...

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