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Ch 5 Microbial Metabolism

Ch 5 Microbial Metabolism. Objectives:. Differentiate between, anabolism, and catabolism. Identify the components of an enzyme and describe the mechanism of enzymatic action. List the factors that influence enzymatic activity. Explain what is meant by oxidation–reduction.

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Ch 5 Microbial Metabolism

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  1. Ch 5Microbial Metabolism

  2. Objectives: Differentiate between, anabolism, and catabolism. Identify the components of an enzyme and describe the mechanism of enzymatic action. List the factors that influence enzymatic activity. Explain what is meant by oxidation–reduction. Describe the chemical reactions of glycolysis. Explain the products of the Krebs cycle. Describe the chemiosmotic model for ATP generation. Compare and contrast aerobic and anaerobic respiration. Describe the chemical reactions and some products of fermentation. Categorize the various nutritional patterns among organisms according to energy and carbon source.

  3. Catabolic and Anabolic Reactions • Metabolism: The sum of all chemical reactions in an organism • Catabolism: Provides energy and building blocks for anabolism. • Anabolism: Uses energy and building blocks to build large molecules

  4. Role of ATP in Coupling Reactions A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell. Metabolic pathways are determined by enzymes, which are encoded by genes. Fig 5.1

  5. 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

  6. Enzymes lower Activation Energy Compare to Fig 5.2

  7. Fig 5.3 Enzymes • Biological catalysts; specific; not used up in that reaction • Enzyme components: • Apoenzymes, Cofactors, Holoenzymes • Coenzymes (NAD+, NADP+, FAD) • Naming of enzymes (see Table 5.1): Lactate dehydrogenase; Cytochromeoxidase; ligase, transferase etc.

  8. Mechanism of Enzymatic Reactions Compare to Fig 5.4

  9. Factors Influencing Enzyme Activity Enzymes can be denatured by temperature and pH Fig 5.5c Fig 5.6 Substrate concentration influencing enzyme activity

  10. Inhibitors Noncompetitive – allosteric inhibitors vs Competitive inhibitors Fig 5.7

  11. Sulfa drugs

  12. Feedback Inhibition Also known as end-product inhibition Controls amount of substance produced by a cell Mechanism is allosteric inhibition Fig 5.8

  13. Energy Production: Oxidation-Reduction Reactions Redox reaction = oxidation reaction paired with reduction reaction. • Oxidation = removal of e- • Reduction = gain of e- Fig 5.9

  14. Oxidation-Reduction cont. In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations. Fig 5.10

  15. The Generation of ATP Phosphorylation: • Substrate level phosphorylation:transfer of a high-energy PO4– to ADP. • Oxidative phosphorylation: transfer of electrons from one compound to another is used to generate ATP by chemiosmosis.

  16. Metabolic Pathways of Energy Production: COH Catabolism • Cellular respiration • Aerobic respiration • Anaerobic respiration • Fermentation The three steps of aerobic respiration • Glycolysis (oxidation of _____ to ______) • Krebs cycle (oxidation of acetyl CoA to ___) • Oxidative phosphorylation (e- transport chain)

  17. Glycolysis Multi – step breakdown of glucose into pyruvate Generates • small amount of ATP(how many?) • small amount of reducing power – (?) • Alternative pathways: Pentose phosphate and Entner-Doudoroff

  18. The Steps of Glycolysis Compare to Fig. 5.12

  19. Krebs Cycle • Other names? • Transition step generates acetyl-CoA from pyruvate (decarboxylation) • Acetyl group of acetyl-CoA enters TCA cycle • Generates ATP and reducing power • Generates precursor metabolites

  20. Krebs Cycle Compare to Fig 5.13

  21. Electron Transport Chain • Formed by series of electron carriers (cytochromes) located in ___________ • Oxidation/Reduction reactions. Electron carriers (reducing power) from glycolysis and TCA cycle transfer their electrons to the electron transport chain • Generates proton gradient or proton motive force(pmf) • In chemiosmosis, pmf generates energy via oxidative phosphorylation

  22. Electron Transport and the Chemiosmotic Generation of ATP Fig. 5.16

  23. Overview of Respiration and Fermentation Foundation Figure Fig 5.11

  24. Fig 5.17

  25. Anaerobic Respiration • Inorganicmolecule is final electron acceptor, e.g.: • NO3- • SO42- • ATP yield lower than in aerobic respiration because only part of Krebs cycle operates under anaerobic conditions.

  26. Fermentation • Any spoilage of food by microorganisms (general use) • Any process that produces alcoholic beverages or acidic dairy products (general use) • Any large-scale microbial process occurring with or without air (common definition used in industry) Scientific definition: • Uses an organic molecule as the final electron acceptor • Does not use the Krebs cycle or ETC • Energy yield low • Diversity of end products: _____________________ (see Table 5.4)

  27. The Relationship of Fermentation to Glycolysis Not in book Also view Fig 5.18

  28. Location of Carbohydrate Catabolism

  29. Energy produced from complete oxidation of one glucose molecule using aerobic respiration

  30. ATP produced from complete oxidation of one glucose using aerobic respiration

  31. Carbohydrate Catabolism • 36 ATPs are produced in eukaryotes

  32. Catabolism of Other Compounds • Polysaccharides and disaccharides • Amylases for digestion of ___________ (very common) • Cellulase for digestion of cellulose (only bacteria and fungi have this enzyme) • Disaccharidases • Lipid catabolism not covered

  33. Decarboxylation Protein Catabolism Extracellular proteases Protein Amino acids Deamination, decarboxylation, dehydrogenation, desulfurylation Krebs cycle Organic acid

  34. Biochemical Tests and Bacterial Identification: Fermentation Tests Different species produce different enzymes  test detects enzyme Mannitol Fermentation:

  35. Metabolic Diversity among Organisms • Energy source: Phototrophs vs. Chemotrophs • Principal carbon source: Autotrophs vs. Heterotrophs • Chemoheterotrophsuse same organic compound as energy source and carbon source. Most medically important bacteria. • Saprophytes vs. parasites

  36. Anabolic Pathways Biosynthesis not covered, except for Protein biosynthesis (see Ch 8) the end

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