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CHAPTER 20 SPECIFIC CATABOLIC PATHWAYS LIPIDS

CHAPTER 20 SPECIFIC CATABOLIC PATHWAYS LIPIDS. ADIPOSE TISSUE. 90% of adipose tissue is triglycerides It supplies energy. Insulation. Provides minor physical protection Cholestrol storage . HYDROLYSIS. GLYCEROL. GLUCOSE. GLYCOLYSIS. PYRUVATE. b -Oxidation.

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CHAPTER 20 SPECIFIC CATABOLIC PATHWAYS LIPIDS

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  1. CHAPTER 20 SPECIFIC CATABOLIC PATHWAYS LIPIDS

  2. ADIPOSE TISSUE • 90% of adipose tissue is triglycerides • It supplies energy. • Insulation. • Provides minor physical protection • Cholestrol storage

  3. HYDROLYSIS

  4. GLYCEROL GLUCOSE GLYCOLYSIS PYRUVATE

  5. b-Oxidation • -Oxidation: a series of five enzyme-catalyzed reactions that cleaves carbon atoms two at a time from the carboxyl end of a fatty acid. • Reaction 1: the fatty acid is activated by conversion to an acylCoA

  6. -OXIDATION Blue box =  carbon Red box = acetyl CoA

  7. -OXIDATION • Activation by addition Coenzyme-A •  carbon oxidized from CH2 to C=O (ketone) • Molecule split into acetyl CoA and Fatty acid 2 carbons shorter • Another Coenzyme-A added to shortened Fatty acid

  8. Each cycle produces 1 acetyl-CoA 18 carbon fatty acid would give 9 acetyl-CoA Cycles required is # of carbons/2 – 1 18 carbon fatty acid would require 8 cycles Amount of energy from Fatty Acid depends on length of carbon chain 18 carbon fatty acid would give 146 ATP

  9. Fatty Acid Biosynthesis • While degradation of fatty acids takes place in mitochondria, the majority of fatty acid synthesis takes place in the cytosol. • These two pathways have in common that they both involve acetyl CoA. • Acetyl CoA is the end product of each spiral of b-oxidation. • Fatty acids are synthesized two carbon atoms at a time. • The source of these two carbons is the acetyl group of acetyl CoA. • The key to fatty acid synthesis is a multienzyme complex called acyl carrier protein, ACP-SH.

  10. Fatty Acid Biosynthesis • ACP has a side chain that carries the growing fatty acid • ACP rotates counterclockwise, and its side chain sweeps over the multienzyme system (empty spheres).

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