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CHAPTER 5

CHAPTER 5. MICROBIAL METABOLISM. Energy Chemical work Transport work Mechanical work Laws of thermodynamics 1 st 2 nd – entropy. Two fundamental tasks required for growth and reproduction Catabolism Anabolism. Metabolism Amazing diversity but also unity

evan-mcpherson
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CHAPTER 5

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  1. CHAPTER 5 MICROBIAL METABOLISM

  2. Energy • Chemical work • Transport work • Mechanical work • Laws of thermodynamics • 1st • 2nd – entropy

  3. Two fundamental tasks required for growth and reproduction • Catabolism • Anabolism

  4. Metabolism • Amazing diversity but also unity • Ordered, enzyme-mediated pathways • ATP • Redox

  5. Catabolic reactions • hydrolytic, exergonic (-ΔG) • Keq>1, spontaneous • Cellular respiration • Provides precursor molecules and energy for anabolic reactions

  6. Anabolic reactions • dehydration synthesis, endergonic (+ΔG) • Keq<1, not favorable • protein synthesis • Consumes energy and precursor molecules in the biosynthesis of macromolecules

  7. Amphibolic reactions

  8. Energy of Activation (EA) • Catalysts (influence reaction rate): • Temperature • Substrate Concentration • Enzymes – biological catalysts

  9. Enzymes: • All protein or holoenzymes • Apoenzyme + Cofactor (coenzyme)

  10. Characteristics of enzymes • do not make reactions happen that could not happen on their own • not permanently altered or used up • substrate-specific • Function is based on structure

  11. Six functional categories of enzymes:

  12. Unconventional Enzymes • Ribozymes • Novel type of RNA • Extremozymes • Have molecular applications

  13. Mechanism of Enzymatic Action Induced Fit model

  14. Factors influencing enzyme activity • Denaturing stresses • Heat, pH, UV radiation, chemicals • Substrate concentration • Competitive inhibition • Non-competitive (allosteric) inhibition

  15. Feedback Inhibition • Negative allosteric effection

  16. Reduction-Oxidation Reactions • Redox reactions liberate energy • always coupled • oxidation (electron donor) • reduction (electron acceptor) • Standard reduction potential (E`O) • Reducing power (potential energy)

  17. Reduction of NAD – common electron carrier • Electrons and protons are typically removed together • The equivalent of a hydrogen atom

  18. NAD and FAD are common electron carriers

  19. E’0 of various biologically important redox couples Electrons moving toward less negative acceptors release free energy Amount of energy released correlates with magnitude of difference in E’0

  20. ATP Synthesis • Free energy used to phosphorylate ADP forms ATP –metabolic money!

  21. Substrate level phosphorylation • chemical energy • Oxidative phosphorylation • energy from proton motive force • Photophosphorylation • radiant energy

  22. Heterotrophic Metabolism • Oxidize energy (electron) rich organic molecules • Typically utilize carbohydrates • Glucose (C6H12O6) is #1 source

  23. Three possible pathways based on final electron receptor • Aerobic respiration – exogenous (oxygen) • Anaerobic respiration – exogenous • Fermentation – endogenous organic

  24. pathways are amphibolic and provide • Energy • Reducing power • Precursor metabolites

  25. Respiration uses reducing power to generate ATP • NADH and FADH2 provide electrons to power proton motive force • Terminal electron acceptor varies • Oxygen in aerobic respiration • Anaerobic respiration uses alternate inorganic molecule

  26. GLYCOLYSIS • Embden-Meyerhof Pathway • Common pathway • Glucose (6C) partially broken down into 2 molecules of pyruvate (3C) • Anerobic; cytoplasm • 2 NADH; 4 ATP • 2 ATP consumed; so net gain of 2 ATP • Substrate level phosphorylation

  27. Pentose phosphate pathway • Produces many intermediate materials for other pathways • glyceraldehyde 3-phosphate, fructose 6-phosphate, ribulose 5-phosphate • If only 5 carbon sugars are available it can biosynthesize 6 carbon sugars • Major contributor to biosynthesis • reducing power in NADPH • vital precursor metabolites for anabolic pathways • intermediates may be used to generate ATP

  28. Pentose phosphate pathway

  29. Entner-Doudoroff pathway • Alternate pathway to glycolysis • typically not seen in G+ bacteria • major contributor to biosynthesis • reducing power as NADH and NADPH • vital precursor metabolites for anabolic pathways

  30. Entner-Doudoroff pathway

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