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Understanding Microbial Metabolism and Enzymes

Learn about microbial metabolism, enzymes, ATP generation, carbohydrate catabolism, Krebs cycle, and more in this comprehensive guide.

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Understanding Microbial Metabolism and Enzymes

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  1. Chapter 5 - Microbial Metabolism • Metabolism is all of the chemical reactions in an organism. • is the energy-releasing processes. • Occurs when molecular bonds (and thus, molecules) are broken down. • Generates ATP • is the energy-using processes. • Occurs when molecular bonds (and thus, molecules) are formed. • Uses ATP

  2. Enzymes • Biochemical catalysts • Specific for a chemical reaction • protein portion • Nonprotein component • Coenzyme: Organic cofactor • Holoenzyme: Apoenzyme + cofactor

  3. Enzymes Figure 5.3

  4. Factors Influencing Enzyme Activity • pH • pH extremes will denature enzymes Figure 5.5b

  5. Factors Influencing Enzyme Activity • Temperature • Very high temperatures will denature enzymes Figure 5.5a

  6. Factors Influencing Enzyme Activity • Substrate concentration Figure 5.5c

  7. Factors Influencing Enzyme Activity • Competitive inhibition Figure 5.7a, b

  8. Factors Influencing Enzyme Activity • Noncompetitive inhibition Figure 5.7a, c

  9. Factors Influencing Enzyme Activity • Feedback inhibition: A pathway endproduct (or intermediate) binds to an enzyme in the pathway, stopping the pathway Figure 5.8

  10. Oxidation-Reduction • is the loss of electrons. • is the gain of electrons. • Redox reaction is an oxidation reaction paired with a reduction reaction.

  11. The Generation of ATP • ATP is the main energy currency in living cells • Energy released from the transfer of electrons of one compound to another is used to generate ATP.

  12. Carbohydrate Catabolism • The breakdown of carbohydrates to release energy • Glycolysis • Krebs cycle • Electron transport chain

  13. Glycolysis • The oxidation of glucose to pyruvic acid; produces • Preparatory Stage • 2 ATPs are used • Glucose is split to form two Glyceraldehyde-3-phosphates

  14. Preparatory Stage Preparatory Stage Glucose 1 Glucose 6-phosphate 2 Fructose 6-phosphate 3 Fructose 1,6-diphosphate 4 5 Glyceraldehyde 3-phosphate (GP) Dihydroxyacetone phosphate (DHAP) Figure 5.12.1

  15. Energy-Conserving Stage • Two Glyceraldehyde-3-phosphates oxidized to 2 Pyruvic acids • 4 ATP produced • 2 NADH produced

  16. Energy-Conserving Stage 6 1,3-diphosphoglyceric acid 7 3-phosphoglyceric acid 8 2-phosphoglyceric acid 9 Phosphoenolpyruvic acid (PEP) 10 Pyruvic acid Figure 5.12.2

  17. Krebs Cycle • Preparatory Step: • Pyruvic acid (from glycolysis) is oxidized and decarboyxlated • Acetyl CoA is produced

  18. Preparatory Step Figure 5.13.1

  19. Krebs Cycle • Oxidation of acetyl CoA produces 6 NADH and 2 FADH2 • 2 ATP produced; CO2 produced

  20. Krebs Cycle Figure 5.13.2

  21. The Electron Transport Chain • A series of molecules that pass electrons down the chain. (oxidation – reduction reactions) • Energy released can be used to produce ATP by

  22. Electron Transport Chain and Chemiosmosis Figure 5.16.2

  23. Cellular Respiration • The final electron acceptor in the electron transport chain is O2. • The final electron acceptor in the electron transport chain is not O2. Net Yield: • 1 Glucose oxidized aerobically = ~38 ATP • 1 Glucose oxidized anaerobically = much less ATP

  24. Chemiosmosis Figure 5.15

  25. Fermentation • Does not require oxygen • Does not use the Krebs cycle or ETC • Uses an organic molecule as the final electron acceptor • Alcohol fermentation. Produces ethyl alcohol + CO2 • Lactic acid fermentation. Produces lactic acid.

  26. Photosynthesis • Conversion of light energy into chemical energy (ATP), and the synthesis of sugar • Light-dependent reaction (Light reaction) • Produces ATP and NADPH • Light-independent reaction (Calvin cycle) • Uses ATP and NADPH to make sugar

  27. Metabolic Diversity • Autotrophs: Use CO2 as main carbon source • photoautotrophs: Derive energy from sun • chemoautotrophs: Derive energy from inorganic compounds

  28. Metabolic Diversity • Heterotrophs: Use organic compounds as carbon source • Photoheterotrophs: Derive energy from sun; carbon from organic compounds • Chemoheterotrophs: Generally, derive energy and carbon from organic compounds

  29. Polysaccharide Biosynthesis Figure 5.28

  30. Lipid Biosynthesis Figure 5.29

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