Chapter29 - 29. The Organic Chemistry of Metabolic Pathways...

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29. The Organic Chemistry of Metabolic Pathways Based on McMurry’s Organic Chemistry , 6 th edition ©2003 Ronald Kluger Department of Chemistry University of Toronto
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 2 29.1 An Overview of Metabolism and Biochemical Energy Metabolism: The reactions in organisms Catabolism: Pathways that break down larger molecules into smaller ones Usually release energy Anabolism: Pathways that synthesize larger biomolecules from smaller ones Usually requires an input of energy
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 3 The First Catabolic Stage: Digestion Food is broken down by hydrolysis of esters, glycosides, and peptide in the digestive system Yields fatty acids, simple sugars, and amino acids Smaller molecules are degraded in cells to acetyl groups attached to the large carrier molecule coenzyme A
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 4 Coenzyme A A complex thiol that transports acyl groups in enzyme reactions Most commonly as acetyl derivative Derived from pantetheine, a vitamin
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 5 Acetyl Coenzyme A The acetyl ester of Coenzyme A (acetyl CoA) Key substance in numerous other biological pathways
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 6 Conversion of Food to Energy: Initial Digestion Digestion begins with enzymes that break down complex macromolecules For example, proteins are converted to peptides and then amino acids Complex carbohydrates are broken down to simple sugars Fats are hydrolyzed to acids and glycerol
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 7 Breakdown of Smaller Molecules Sugars and fat components are broken down in steps that lead to formation of acetate Some steps are coupled to formation of phosphate anhydrides Amino acids are recycled into proteins
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 8 Oxidation of Acetyl Groups Acetyl groups are oxidized inside cellular mitochondria in the the citric acid cycle to yield CO 2 The oxidation process releases energy in matched stages These reactions are coupled to an electron-transport chain (successive reduction) The energy available drives a dehydration reaction that forms to produce molecules of the nucleotide adenosine triphosphate , ATP (shown on the next slide)
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 9 Formation of ATP Energy in electron transport (stepwise oxidation) provides energy for formation of ATP from ADP with elimination of water
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 10 The Role of ATP Catabolic reactions "pay off" in ATP by synthesizing it Anabolic reactions "spend" ATP by transferring the terminal phosphate group while regenerating ADP The transfer of phosphate from ATP to water (hydrolysis) gives off energy that can be used for another reaction!
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Based on McMurry, Organic Chemistry, Chapter 29, 6th 11 Phosphoric Acid Anhydrides Phosphoric acid (H 3 PO 4
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Chapter29 - 29. The Organic Chemistry of Metabolic Pathways...

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