Lecture 29 - 29 The Organic Chemistry of Metabolic Pathways Based on McMurry's Organic Chemistry 7th edition Why this Chapter To examine some of

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29. The Organic Chemistry of Metabolic Pathways Based on McMurry’s Organic Chemistry , 7 th edition
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2 Why this Chapter? To examine some of the pathways by which organisms carry out their chemistry To give us an idea of the kinds of processes that may occur
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3 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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4 Catabolism Food is broken down by hydrolysis of esters, glycosides, and peptides 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 Examine Figure 29.1
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5 Acetyl Coenzyme A The acetyl ester of Coenzyme A (acetyl CoA) Key substance in numerous other biological pathways
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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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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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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 molecules of the nucleotide adenosine triphosphate , ATP (shown on the next slide)
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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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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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11 Phosphorylation ATP reacts with alcohols in enzyme reactions to produce esters of phosphoric acids, called phosphate esters The process is called phosphorylation
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12 Metabolic Use of ATP An endergonic reaction has a thermodynamic barrier in addition to a kinetic barrier Enzymes can cut kinetic barriers only Combining the reaction with an exergonic process (hydrolysis of ATP) converts the energetics of the total process The endergonic reaction is "coupled" to an energetically favorable reaction so that the overall free-energy change for the two reactions together is favorable
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This note was uploaded on 09/06/2009 for the course CHEM chem 12 AB taught by Professor Adamczeski during the Spring '09 term at San Jose City College.

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Lecture 29 - 29 The Organic Chemistry of Metabolic Pathways Based on McMurry's Organic Chemistry 7th edition Why this Chapter To examine some of

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