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Q&A. All E. coli look alike through a microscope; so how can E. coli O157 be differentiated?. Catabolic and Anabolic Reactions. Learning Objectives. 5-1 Define metabolism , and describe the fundamental differences between anabolism and catabolism.

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  1. Q&A • All E. coli look alike through a microscope; so how can E. coli O157 be differentiated?

  2. Catabolic and Anabolic Reactions Learning Objectives 5-1 Define metabolism, and describe the fundamental differences between anabolism and catabolism. 5-2 Identify the role of ATP as an intermediate between catabolism and anabolism.

  3. Catabolic and Anabolic Reactions • Metabolism: The sum of the chemical reactions in an organism

  4. Catabolic and Anabolic Reactions • Catabolism: Provides energy and building blocks for anabolism. • Anabolism: Uses energy and building blocks to build large molecules

  5. Role of ATP in Coupling Reactions Figure 5.1

  6. ANIMATION Metabolism: Overview Catabolic and Anabolic Reactions • A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell • Metabolic pathways are determined by enzymes • Enzymes are encoded by genes

  7. Check Your Understanding • Distinguish catabolism from anabolism. 5-1 • How is ATP an intermediate between catabolism and anabolism? 5-2

  8. Enzyme Learning Objectives 5-3 Identify the components of an enzyme. 5-4 Describe the mechanism of enzymatic action. 5-5 List the factors that influence enzymatic activity. 5-6 Distinguish competitive and noncompetitive inhibition. 5-7 Define ribozyme.

  9. Collision Theory • The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide • Activation energy is needed to disrupt electronic configurations • Reaction rate is the frequency of collisions with enough energy to bring about a reaction. • Reaction rate can be increased by enzymes or by increasing temperature or pressure

  10. Energy Requirements of a Chemical Reaction Figure 5.2

  11. Enzyme Components • Biological catalysts • Specific for a chemical reaction; not used up in that reaction • Apoenzyme: Protein • Cofactor: Nonprotein component • Coenzyme: Organic cofactor • Holoenzyme: Apoenzyme plus cofactor

  12. Components of a Holoenzyme Figure 5.3

  13. Important Coenzymes • NAD+ • NADP+ • FAD • Coenzyme A

  14. ANIMATION Enzymes: Overview ANIMATION Enzymes: Steps in a Reaction Enzyme Specificity and Efficiency • The turnover number is generally 1 to 10,000 molecules per second

  15. The Mechanism of Enzymatic Action Figure 5.4a

  16. The Mechanism of Enzymatic Action Figure 5.4b

  17. Enzyme Classification • Oxidoreductase: Oxidation-reduction reactions • Transferase: Transfer functional groups • Hydrolase: Hydrolysis • Lyase: Removal of atoms without hydrolysis • Isomerase: Rearrangement of atoms • Ligase: Joining of molecules, uses ATP

  18. Factors Influencing Enzyme Activity • Temperature • pH • Substrate concentration • Inhibitors

  19. Factors Influencing Enzyme Activity • Temperature and pH denature proteins Figure 5.6

  20. Effect of Temperature on Enzyme Activity Figure 5.5a

  21. Effect of pH on Enzyme Activity Figure 5.5b

  22. Effect of Substrate Concentration on Enzyme Activity Figure 5.5c

  23. Enzyme Inhibitors: Competitive Inhibition Figure 5.7a–b

  24. ANIMATION Competitive Inhibition Enzyme Inhibitors: Competitive Inhibition

  25. ANIMATION Non-competitive Inhibition Enzyme Inhibitors: Noncompetitive Inhibition Figure 5.7a, c

  26. Enzyme Inhibitors: Feedback Inhibition Figure 5.8

  27. Ribozymes • RNA that cuts and splices RNA

  28. Check Your Understanding • What is a coenzyme? 5-3 • Why is enzyme specificity important? 5-4 • What happens to an enzyme below its optimal temperature? • Above its optimal temperature? 5-5 • Why is feedback inhibition noncompetitive inhibition? 5-6 • What is a ribozyme? 5-7

  29. Energy Production Learning Objectives 5-8 Explain the term oxidation-reduction. 5-9 List and provide examples of three types of phosphorylation reactions that generate ATP. 5-10 Explain the overall function of metabolic pathways.

  30. Oxidation-Reduction Reactions • Oxidation: Removal of electrons • Reduction: Gain of electrons • Redox reaction: An oxidation reaction paired with a reduction reaction

  31. Oxidation-Reduction Figure 5.9

  32. ANIMATION Oxidation-Reduction Reactions Oxidation-Reduction Reactions • In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.

  33. Representative Biological Oxidation Figure 5.10

  34. The Generation of ATP • ATP is generated by the phosphorylation of ADP

  35. Substrate-Level Phosphorylation • Energy from the transfer of a high-energy PO4– to ADP generates ATP

  36. Oxidative Phosphorylation • Energy released from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP in the electron transport chain

  37. Metabolic Pathways of Energy Production

  38. Check Your Understanding • Why is glucose such an important molecule for organisms? 5-8 • Outline the three ways that ATP is generated. 5-9 • What is the purpose of metabolic pathways? 5-10

  39. Carbohydrate Catabolism Learning Objectives 5-11 Describe the chemical reactions of glycolysis. 5-12 Identify the functions of the pentose phosphate and Entner-Doudoroff pathways. 5-13 Explain the products of the Krebs cycle. 5-14 Describe the chemiosmotic model for ATP generation. 5-15 Compare and contrast aerobic and anaerobic respiration. 5-16 Describe the chemical reactions of, and list some products of, fermentation

  40. Carbohydrate Catabolism • The breakdown of carbohydrates to release energy • Glycolysis • Krebs cycle • Electron transport chain

  41. Glycolysis • The oxidation of glucose to pyruvic acid produces ATP and NADH Figure 5.11

  42. Preparatory Stage of Glycolysis • 2 ATP are used • Glucose is split to form 2 glucose-3-phosphate Figure 5.12, steps 1–5

  43. Energy-Conserving Stage of Glycolysis • 2 glucose-3-phosphate oxidized to 2 pyruvic acid • 4 ATP produced • 2 NADH produced Figure 5.12, steps 6–10

  44. ANIMATION Glycolysis: Overview ANIMATION Glycolysis: Steps Glycolysis • Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+ 2 pyruvic acid + 4 ATP + 2 NADH + 2H+

  45. Alternatives to Glycolysis • Pentose phosphate pathway • Uses pentoses and NADPH • Operates with glycolysis • Entner-Doudoroff pathway • Produces NADPH and ATP • Does not involve glycolysis • Pseudomonas, Rhizobium, Agrobacterium

  46. Cellular Respiration • Oxidation of molecules liberates electrons for an electron transport chain • ATP is generated by oxidative phosphorylation

  47. Intermediate Step • Pyruvic acid (from glycolysis) is oxidized and decarboyxlated Figure 5.13

  48. ANIMATION Krebs Cycle: Overview ANIMATION Krebs Cycle: Steps The Krebs Cycle • Oxidation of acetyl CoA produces NADH and FADH2

  49. The Krebs Cycle Figure 5.13

  50. ANIMATION Electron Transport Chain: Overview The Electron Transport Chain • A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain • Energy released can be used to produce ATP by chemiosmosis

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