Chapter 5 Metabolism

1. Chapter 5Metabolism

4. 3 Questions About Microbial Metabolism • How do microbes metabolize glucose? • How do microbes generate ATP? • How do microbes get around abnormal conditions?

5. 3 Ways to Metabolize Glucose • Glycolysis • Pentose Phosphate • Entner-Doudoroff Pathway.

6. Glycolysis (Embden Meyerhof) • Major route to pyruvate (sweet loosening) • Has 6 C stage and 3 C stage • net 2 ATP’s (substrate level phos.) • Pathway p. 138 (transparency).

9. Functions of Glycolysis • Major route of hexoses to pyruvate • Provides 6/12 critical intermediates • Generates energy.

10. Limitations of Glycolysis • Still need 5 carbon sugars (DNA, RNA) • Erythrose - 4 Phosphate needed for aromatic amino acids • Need NADPH.

11. Don’t Worry Be Happy! Solution for Most Microbes is Pentose Phosphate Pathway

12. Pentose Phosphate Pathway - Hexose Monophosphate Shunt • Can occur aerobically or anaerobically • Two enzymes critical • transketolase: transfers 2-carbon molecules • transaldolase: transfers 3-carbon molecules • Pathway p. 140 (transparency).

15. Functions of Pentose Phosphate • Generates NADPH • Generates 4 and 5-carbon sugars • Ribose 5 Phosphate • Intermediates used to make ATP.

16. Entner - Doudoroff Pathway • Alternative to Pentose P. & Glycolysis • Provides 5/12 critical metabolites • Pathway p. 174 (transparency) • Found in Pseudomonas, Rhizobium, Azotobacter, Enterococcus.

17. Glycolysis vs. Entner Doudoroff • Both convert glucose to two molecules of pyruvate • In ED, one pyruvate from top half, other from G3P • In glycolysis, both pyruvates arise from G3P. • ATP from ED 1/2 of Glycolysis.

19. Tricarboxylic Acid Cycle (Krebs) • Provides remaining intermediates • Generates energy NADH & FADH2 • Found in all aerobes & most anaerobes • Amphibolic • Pathway p. 183 (transparency).

21. ATP Generation • Substrate Level Phosphorylation • Photophosphorylation • Oxidative Phosphorylation.

22. Electron Transport • Electrons progressively transferred from donors to acceptors • Passed from NADH and FADH2 to electron carriers in membrane • Ends at terminal electron acceptors -- oxygen.

23. Electron Transport • High potential difference = energy production • ET produces proton gradients --- makes ATP.

24. e- H2 2H+ Electron Transport

25. e- H2 2H+ Electron Transport

26. e- H2 2H+ Electron Transport

27. ATP e- H2 2H+ Electron Transport

28. e- H2 2H+ Electron Transport

29. e- H2 2H+ Electron Transport

30. e- H2 2H+ ATP O2 Electron Transport H2O

31. Oxidative Phosphorylation • Production of ATP at expense of proton motive force from ET.

33. Fermentation • Without O2, NADH not oxidized by ET • NADH (glycolysis) must be oxidized • Some use pyruvate as terminal electron acceptor • Organic molecules are terminal electron acceptors.

35. Fermentation Types

37. Anaerobic Respiration • Terminal electron acceptors inorganic - nitrate, sulfate, carbon dioxide • Not as efficient at ATP synthesis as aerobic.

38. Anaerobic Respiration Types • Dissimilatory Nitrate Reduction: nitrate reduced to nitrite • Denitrification: nitrate reduced to nitrogen gas (Pseudomonas, Bacillus) • Sulfate Reduction: sulfate reduced to sulfide (Desulfovibrio) • Methanogenesis: carbon dioxide converted to methane.

39. Microbes for Sale!