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Microbiology. Chapter 8. Part I. Enzymes. Enzymes Catalyze Chemical Reactions of Life. Increase reaction rates without being consumed by the reaction Lower the activation energy Active site is where the substrate binds Active site is where chemistry happens

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Presentation Transcript

  1. Microbiology Chapter 8

  2. Part I Enzymes

  3. Enzymes Catalyze Chemical Reactions of Life • Increase reaction rates without being consumed by the reaction • Lower the activation energy • Active site is where the substrate binds • Active site is where chemistry happens • Chemistry is performed by side chains of amino acids • Cofactors or coenzymes • Active site has specificity

  4. Reaction Coordinate • Description of energy changes during the reaction • Horizontal axis is charts the progessive chemical changes (bond breakage/bond formation) as S is converted into P • Vertical axis represents Energy • Transition state – not a reaction intermediate • Fleeting molecular moment in which bond breakage, bond formation are happening

  5. Reaction Coordinate ∆G’º = -RTlnK’eq Just because delta G is favorable does not mean that the reaction is fast

  6. Enzyme Terminology • Holoenzyme • Is a combination of protein (apoenzyme) and one or more cofactors • Cofactors • Coenzyme – complex organic molecules • Metal ions

  7. Enzyme Structure • Holoenzyme • Apoenzyme – protein • Cofactors – complex organic molecules • Coenzyme – metal ions • Active site usually contains the cofactors and coenzymes because they are crucial for the chemistry

  8. Cofactors

  9. Enzyme Substrate Interactions • Specificity of active site – induced fit • Bonds between substrate and enzyme are weak and reversible • Once the enzyme substrate complex has formed chemical reactions occur on the substrate and the product is released • Most enzyme reactions are reversible with the exception of enzymes which regulate metabolic pathways

  10. Lysozyme Reaction

  11. Lysozyme Reaction

  12. Types of Enzyme Inhibition

  13. Enzyme Location

  14. Synthesis and Hydrolysis Reactions

  15. Enzymes in Disease • Virulence Factors • Enzymes that are excreted from microorganisms that contribute to the pathogenicity of diseases

  16. Virulence Factors • Streptococcus pyogenes – throat and skin infections • Streptokinase – digests blood clots and assists in wound invasion • Pseudomonas aeruginose – respiratory and skin pathogen • Elastase and collagenase digestive enzymes • Clostridium perfringens – gas gangrene • Lecithinase C lipase damages cell membranes; therefore massive tissue death

  17. Virulence Factors • Not all virulence factors secrete enzymes which digest tissues • Can protect microbes from effects of drug therapy • Penicillinase • Inactivates penicillin

  18. Enzymes and Their Environment • Why do you think enzymes only function properly under established conditions of pH, temperature • Why do you think agents such as heavy metals and alcohol also have the ability to denature enzymes • Take a look at enzyme structure

  19. Part II Metabolism

  20. Metabolism In Microbes • All chemical reactions of a cell • Two general classes • Anabolism or biosynthesis • Catabolism or degradative reactions

  21. Simplified Model of Metabolism

  22. Metabolic Pathways • The product of one reaction is often the substrate for the next • Every pathway has one or more regulatory enzymes • All other enzymes in the pathway usually are not regulated • They operate whenever the substrate is available

  23. Cell Energetics • Not all cellular reactions are equal with respect to energy • Exergonic – Energy Released • Endergonic – Energy Requiring

  24. Energy Conversions

  25. Three Stages of Metabolism

  26. Glycolysis – Part I

  27. Glycolysis – Part II

  28. GAP to 1,3 BPG

  29. Pyruvate Dehydrogenase Complex

  30. TCA Cycle

  31. Structure of FAD and NAD+ • Both are electron carriers in the ETC

  32. What is the purpose of NADH • The electron transport chain transfers electrons from NADH to other electron carriers • The electrons end up on various molecules • However, electron movement is associated with making a proton gradient • Proton gradient is responsible for ATP production

  33. NAD

  34. Electron Transport Chain

  35. Electron Transport Chain

  36. Electron Transport Chain

  37. ETC in Humans

  38. ATP Synthase

  39. Is Respiration Coupled to ATP Synthase?

  40. Coupling • How could you uncouple the ETC from the production of ATP • What if you treated a cell with a weak hydophobic acid such as FCCP or DNP

  41. DNP Caused Uncoupling

  42. Aerobic Respiration • Characteristic of many bacteria, fungi, protozoa, and animals • Electrons and hydrogen are taken from highly reduced, high energy compounds • Electrons and hydrogen end up on O2 to form H20 • Much ATP is made

  43. Nutrient Processing • Extremely varied in bacteria • Remember Microbes are classified according to their O2 requirements • Aerobic respiration • Anaerobic respiration • Fermentation

  44. Anaerobic Respiration • System involves the same three pathways as aerobic respiration • Final electron acceptor is not 02 but instead NO3-, SO4-, CO3-

  45. Final Electron Acceptors

  46. Electron Transport In Plants

  47. Comparison of ETC and ATP Synthesis

  48. Other Fates of Pyruvate • Fermentation products can be grouped into two general categories • Alcoholic fermentation • Acidic fermentation

  49. Other Fates of Pyruvate

  50. Anaerobic Metabolism

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