Chapter 5

1. Chapter 5 Microbial Metabolism

2. Basic Chemical Reactions Underlying Metabolism Metabolism Collection of controlled biochemical reactions that take place within a microbe Ultimate function of metabolism is to reproduce the organism © 2012 Pearson Education Inc.

3. Basic Chemical Reactions Underlying Metabolism Metabolic Processes Guided by Eight Elementary Statements Every cell acquires nutrients Metabolism requires energy from light or from catabolism of nutrients Energy is stored in adenosine triphosphate (ATP) Cells catabolize nutrients to form precursor metabolites Precursor metabolites, energy from ATP, and enzymes are used in anabolic reactions Enzymes plus ATP form macromolecules Cells grow by assembling macromolecules Cells reproduce once they have doubled in size © 2012 Pearson Education Inc.

4. Basic Chemical Reactions Underlying Metabolism ANIMATION Metabolism: Overview © 2012 Pearson Education Inc.

5. Basic Chemical Reactions Underlying Metabolism Catabolism and Anabolism Two major classes of metabolic reactions Catabolic pathways Break larger molecules into smaller products Exergonic Anabolic pathways Synthesize large molecules from the products of catabolism Endergonic © 2012 Pearson Education Inc.

6. ISM BOL CATA Energy lostas heat Figure 5.1 Metabolism Energy lostas heat Energyused Energystored ANABOLISM Larger buildingblocks Precursormolecules Macromolecules Energy storage(carbohydrates,lipids, etc.) Nutrients Cellular structures(membranes,ribosomes, etc.) Cellularprocesses(cell growth,cell division, etc.)

7. Basic Chemical Reactions Underlying Metabolism Oxidation and Reduction Reactions Electron transfer from an electron donor to an electron acceptor Reactions always occur simultaneously Cells use electron carriers to carry electrons (often in H atoms) Three important electron carriers Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide phosphate (NADP+) Flavine adenine dinucleotide (FAD) → FADH2 © 2012 Pearson Education Inc.

8. Figure 5.2 Oxidation-reduction, or redox, reactions Reduction Electrondonor Oxidizeddonor Electronacceptor Reduced acceptor Oxidation

9. Basic Chemical Reactions Underlying Metabolism ANIMATION Oxidation-Reduction Reactions © 2012 Pearson Education Inc.

10. Basic Chemical Reactions Underlying Metabolism ATP Production and Energy Storage Organisms release energy from nutrients Stored in high-energy phosphate bonds (ATP) Phosphorylation – organic phosphate is added to substrate Cells phosphorylate ADP to ATP in three ways Substrate-level phosphorylation Oxidative phosphorylation Photophosphorylation Anabolic pathways use some energy by breaking phosphate bonds © 2012 Pearson Education Inc.

11. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzymes are organic catalysts Increase likelihood of a reaction Six categories of enzymes based on mode of action Hydrolases Isomerases Ligases or polymerases Lyases Oxidoreductases Transferases © 2012 Pearson Education Inc.

12. Basic Chemical Reactions Underlying Metabolism ANIMATION Enzymes: Overview © 2012 Pearson Education Inc.

13. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Makeup of enzymes Many protein enzymes are complete in themselves Apoenzymes are inactive if not bound to nonprotein cofactors Binding of apoenzyme and its cofactor(s) yields holoenzyme Some are RNA molecules called ribozymes © 2012 Pearson Education Inc.

14. Figure 5.3 Makeup of a protein enzyme Inorganic cofactor Active site Coenzyme(organiccofactor) Apoenzyme (protein) Holoenzyme

15. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzyme activity Enzymes lower the activation energy Enzyme-substrate specificity Active site complementary to shape of the substrate © 2012 Pearson Education Inc.

16. Figure 5.4 Effect of enzymes on chemical reactions Activation energywithout enzyme Activation energywith enzyme Reactants Energy Products Progress of reaction

17. Figure 5.5 Enzymes fitted to substrates-overview

18. Substrate (Fructose 1,6-bisphosphate) Figure 5.6 The process of enzymatic activity Enzyme (Fructose 1,6-bisphosphatealdolase) Enzyme-substratecomplex Dihydroxyacetone-P Glyceraldehyde-3P Products

19. Basic Chemical Reactions Underlying Metabolism ANIMATION Enzymes: Steps in a Reaction © 2012 Pearson Education Inc.

20. Basic Chemical Reactions Underlying Metabolism The Roles of Enzymes in Metabolism Enzyme activity Many factors influence the rate of enzymatic reactions Temperature pH Enzyme and substrate concentrations Presence of inhibitors Inhibitors Substances that block an enzyme’s active site Do not denature enzymes Three types © 2012 Pearson Education Inc.

21. Figure 5.7 Effects of temperature, pH, and substrate concentration on enzyme activity-overview

22. Figure 5.8 Denaturation of protein enzymes Functional protein Denatured protein

23. Figure 5.9 Competitive inhibition of enzyme activity-overview

24. Basic Chemical Reactions Underlying Metabolism ANIMATION Enzymes-Substrate Interaction: Competitive Inhibition © 2012 Pearson Education Inc.

25. Figure 5.10 Allosteric control of enzyme activity-overview

26. Basic Chemical Reactions Underlying Metabolism ANIMATION Enzyme-Substrate Interaction: Noncompetitive Inhibition © 2012 Pearson Education Inc.

27. Substrate Figure 5.11 Feedback inhibition Pathwayoperates Pathwayshuts down Enzyme 1 Boundend-product(allostericinhibitor) Allostericsite Feedbackinhibition Intermediate A Enzyme 2 Intermediate B End-product Enzyme 3

28. Carbohydrate Catabolism Carbohydrate Catabolism Many organisms oxidize carbohydrates as primary energy source for anabolic reactions Glucose most common carbohydrate used Glucose catabolized by two processes: cellular respiration and fermentation © 2012 Pearson Education Inc.

29. Respiration GLYCOLYSIS Fermentation Glucose Figure 5.12 Summary of glucose catabolism 2 Pyruvic acid Pyruvic acid(or derivative) Formation offermentationend-products Acetyl-CoA KREBSCYCLE ELECTRON TRANSPORT Electrons

30. Carbohydrate Catabolism Glycolysis Occurs in cytoplasm of most cells Involves splitting of a six-carbon glucose into two three-carbon sugar molecules Substrate-level phosphorylation: direct transfer of phosphate between two substrates Net gain of two ATP molecules, two molecules of NADH, and precursor metabolite pyruvic acid © 2012 Pearson Education Inc.

31. Carbohydrate Catabolism ANIMATION Glycolysis: Overview © 2012 Pearson Education Inc.

32. Carbohydrate Catabolism Glycolysis Divided into three stages involving 10 total steps Energy-investment stage Lysis stage Energy-conserving stage © 2012 Pearson Education Inc.

33. Figure 5.13 Glycolysis-overview

34. Carbohydrate Catabolism ANIMATION Glycolysis: Steps © 2012 Pearson Education Inc.

35. Figure 5.14 Example of substrate-level phosphorylation Phosphoenolpyruvate (PEP) Pyruvic acid Holoenzyme Phosphorylation

36. Carbohydrate Catabolism Cellular Respiration Resultant pyruvic acid completely oxidized to produce ATP by series of redox reactions Three stages of cellular respiration 1. Synthesis of acetyl-CoA 2. Krebs cycle 3. Final series of redox reactions (electron transport chain) © 2012 Pearson Education Inc.

37. Fermentation Respiration Pyruvic acid Figure 5.15 Formation of acetyl-CoA Decarboxylation Acetate Coenzyme A Acetyl-coenzyme A(acetyl-CoA)

38. Carbohydrate Catabolism Cellular Respiration Synthesis of acetyl-CoA Results in Two molecules of acetyl-CoA Two molecules of CO2 Two molecules of NADH © 2012 Pearson Education Inc.

39. Carbohydrate Catabolism Cellular Respiration The Krebs cycle Great amount of energy remains in bonds of acetyl-CoA Transfers much of this energy to coenzymes NAD+ and FAD Occurs in cytosol of prokaryotes and in matrix of mitochondria in eukaryotes © 2012 Pearson Education Inc.

40. Carbohydrate Catabolism Cellular Respiration The Krebs cycle Six types of reactions in Krebs cycle Anabolism of citric acid Isomerization reactions Hydration reaction Redox reactions Decarboxylations Substrate-level phosphorylation © 2012 Pearson Education Inc.

41. Respiration Fermentation Acetyl-CoA Figure 5.16 The Krebs cycle OOH OOH OOH OOH Oxaloacetic acid OOH Citric acid OOH OOH OOH Malic acid OOH OOH Isocitric acid KREBSCYCLE OOH HOO Fumaric acid OOH OOH -Ketoglutaric acid OOH OOH OOH Succinic acid Succinyl-CoA

42. Carbohydrate Catabolism ANIMATION Krebs Cycle: Overview © 2012 Pearson Education Inc.

43. Carbohydrate Catabolism ANIMATION Krebs Cycle: Steps © 2012 Pearson Education Inc.

44. Carbohydrate Catabolism Cellular Respiration The Krebs cycle Results in Two molecules of ATP Two molecules of FADH2 Six molecules of NADH Four molecules of CO2 © 2012 Pearson Education Inc.

45. Carbohydrate Catabolism Cellular Respiration Electron transport Most significant ATP production occurs from electron transport chain (ETC) Carrier molecules pass electrons from one to another to final electron acceptor Energy from electrons used to pump protons (H+) across the membrane, establishing a proton gradient Located in cristae of eukaryotes and in cytoplasmic membrane of prokaryotes © 2012 Pearson Education Inc.

46. Respiration Fermentation Figure 5.17 An electron transport chain Path of electrons Reduced FMN Oxidized Oxidized FeS Reduced Reduced Oxidized CoQ 2 Oxidized Cyt Reduced Reduced Oxidized Cyt 2 Oxidized Cyt 2 Reduced 2 Final electronacceptor

47. Carbohydrate Catabolism ANIMATION Electron Transport Chain: Overview © 2012 Pearson Education Inc.

48. Carbohydrate Catabolism Cellular Respiration Electron transport Four categories of carrier molecules Flavoproteins Ubiquinones Metal-containing proteins Cytochromes Aerobic respiration: oxygen serves as final electron acceptor Anaerobic respiration: molecule other than oxygen serves as final electron acceptor © 2012 Pearson Education Inc.

49. Bacterium Mitochondrion Intermembranespace Matrix Exterior Figure 5.18 One possible arrangement of an electron transport chain Cytoplasmicmembrane Cytoplasm Exterior of prokaryoteor intermembrane spaceof mitochondrion FMN Ubiquinone Cyt b Cyt a3 Phospholipidmembrane Cyt c Cyt a Cyt c2 NADHfrom glycolysis,Krebs cycle,pentose phosphatepathway, andEntner-Doudoroffpathway FADH2from Krebs cycle ATP synthase Cytoplasm of prokaryoteor matrix of mitochondrion

50. Carbohydrate Catabolism ANIMATION Electron Transport Chain: Process © 2012 Pearson Education Inc.