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Chapter 25 Lipid Biosynthesis

Chapter 25 Lipid Biosynthesis. 25.1 The Fatty Acid Biosynthesis and Degradation Pathways Are Different. BIOSYNTHESIS DEGRADATION Cytosol Mitochondria ACP CoA Fatty acid synthase Degradation enzymes

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Chapter 25 Lipid Biosynthesis

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  1. Chapter 25 Lipid Biosynthesis

  2. 25.1 The Fatty Acid Biosynthesis and Degradation Pathways Are Different BIOSYNTHESIS DEGRADATION Cytosol Mitochondria ACP CoA Fatty acid synthase Degradation enzymes NADPH NADH

  3. 25.2 Fatty Acid Synthesis 25.2.1 Hexadecanoate (palmitate) synthesis Transport into the cytosol Formation of acetyl- and malonyl-ACP The elongation cycle of fatty acid synthesis

  4. 1. Tranport of acetyl CoA from the mitochondrial matrix into the cytosol

  5. 2. Formation of acetyl- and malonyl-acyl carrier protein(ACP)

  6. Acetyl CoA Malonyl CoA Acetyl CoA carboxylase Acetyl Malonyl transacylase transacylase Acetyl-ACP Malonyl-ACP HCO3- ATP Pi ADP ACP CoA ACP CoA

  7. 3. The elongation cycle of fatty acid synthesis has four stages for each round of synthesis Condensation Reduction Dehydration Reduction

  8. 25.2.2 Further processing of C16 fatty acids

  9. 25.2.3 Unsaturated fatty acid synthesis Desaturase

  10. 25.2.4 Regulation

  11. 25.3 Metabolism of Triacylglycerols 25.3.1 Breakdown of triacylglycerols Triacylglycerol lipases Glycerol + Free fatty acids Glycolysis Oxidation 3H2O 3H+

  12. 25.3.2 Synthesis of triacylglycerols Glycerol 3-phosphate dihydroxyacetone phosphate glycerol Acyl CoA

  13. Pi Triacylglycerol Diacylglycerol

  14. 25.3.3 Regulation cAMP Glucagon Epinephrine Insulin Norepinephrine cAMP-dependent ATPprotein kinaseADP Inactive Active hormone- hormone- sensitive sensitive lipase lipase Pi Insulin - + + +

  15. 25.4 Cholesterol 25.4.1 Cholesterol biosynthesis Acetyl-CoA MVA IPP Squalene Lanosterol Cholesterol

  16. Acetyl-CoA Mevalonate

  17. Mevalonate IPP Squalene

  18. Squalene Lanosterol Cholesterol

  19. 25.4.2 Biosynthesis of bile acids

  20. 25.4.3 Steroid hormones

  21. 25.5 Transport of Many Lipids Occurs via Lipoprotein Complexes 25.5.1 The structure and synthesis of the lipoproteins Lipoprotein apoprotein (apop)

  22. Chylomicron • Very low density lipoprotein (VLDLs) • Intermediate density lipoprotein (IDLs) • Low density lipoprotein (LDLs) • High density lipoprotein (HDLs)

  23. 25.5.2 Function of the lipoproteins • chylomicrons transport dietary (exogenous) triacylglycerols and cholesterol from the intestines to other tissues in the body. • VLDLs, IDLs and LDLs transport internally produced (endogenous) triacylglycerols and cholesterol from the liver to the tissues. • HDLs transport endogenous cholesterol from the tissues to the liver.

  24. LIVER TARGET CELL INTESTINE LDL VLDL Chylomicrons IDL HDL ADIPOSE TISSUE MUSCLE

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