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Bacterial metabolism

Bacterial metabolism. by E. Börje Lindström. This learning object has been funded by the European Commissions FP6 BioMinE project. Definitions. Metabolism:. - all chemical reactions occurring in a cell. With respect to function:. biosynthesis (anabolic reactions)

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Bacterial metabolism

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  1. Bacterial metabolism by E. Börje Lindström This learning object has been funded by the European Commissions FP6 BioMinE project

  2. Definitions Metabolism: - all chemical reactions occurring in a cell • With respect to function: • biosynthesis (anabolic reactions) • energy production (catabolic reactions) • exergonic reactions: - releases working energy (DG < 0) • endergonic reactions: - consumes energy (DG > 0) • co-enzyme: • a low-molecular-weight molecule, that participates in an enzymatic reaction • excepts and donates electrons and functional groups

  3. Catabolism ATP is produced by: • Photosynthesis - light energy  ATP • Chemo synthesis • chemical energy  ATP • substrate level phosphorylation • oxidative phosphorylation • red-ox reactions • electron donator; Ared  Aox • electron receiver: Box  Bred • Processes in chemo synthesis: • Respiration • Fermentation

  4. Respiration • Box = inorganic substance • Model system: - glucose • 4 processes: • Glycolysis • Oxidative decarboxylation • Krebs cycle (TCA) • Electron transport chain

  5. Glycolysis Embden-Meyerhof-Parnas pathway (EMP) • Occurs in two steps: • Activation • Oxidation (the carbon atom is oxidized) • Summary of the reaction: Glucose + 2 NAD  2 pyruvate + 2 NADH + 2 ATP

  6. Decarboxylation of pyruvate 2 pyruvate + 2 NAD+ + 2 CoASH  2 acetyl~SCoA + 2 NADH

  7. Krebs cycle (TCA) • 2 functions in the cell: • Catalyst in the energy metabolism • Start material for biosynthesis of e.g. Amino acids 2 acetyl~SCoA Krebs (TCA) 2 CO2 2 CO2 2 x 4 NADH

  8. NAD+ FADH2 Ared Bred CYT. …… Aox Box NADH FADH+ ATP ATP ATP Electron transport chain Two (2) functions: • Transfer of electrons from NADH Box • produce ATP (oxidative phosphorylation) • Mechanism: • H atoms from NADH is separated into • e- (electrons)  Box • H+ (protons)  outside of cytoplasm membrane • pH gradient is produced (proton motive force, PMF)

  9. Box examples Process Box • aerobic respiration: - O2 • anaerobic respiration: • NO3-, NO2- • SO42-, S0 • CO2

  10. NO3- SO42- CO2 O2 Box examples, cont. Lake Bred  H2O  NO2- ; NH3 ; N2 Sediment  S2- (black sediment)  CH4 (methane)

  11. Fermentation • Box is an organic substance • often an internal substance • the process is anaerobic • no functional electron transport chain • it can however exist in some micro-organisms Model system: - Glucose (Ox.)  (Red.) Glucose pyruvate End products ( naming the process)  (3 alt.) (7 alt.)

  12. Lactic acid fermentation 1) Homo-fermentative: EMP  Glucose 2 pyruvate + 2 ATP + 2 NADH Ox. Box Red. 2 Lactic acid + 2 NAD+ Application: • Yoghurt • Cheese • Butter • Sausages, etc.

  13. Lactic acid fermentation, cont. 2) Hetero-fermentative: -Phosphoketolase pathway (ox.step) NADH 2 NADH Ox.   Glucose 6-P-gluconate Pyruvate +acetyl~P + CO2 + ATP Ox. ATP Red. 2 NAD+ ethanol NAD+ Lactic acid Summary: Glucose  lactic acid + ethanol + CO2 + ATP Application: • Kefir, etc.

  14. Ethanol fermentation Organism: - Saccharomyces cerevisiae (yeast) EMP  Glucose 2 pyruvate + 2 ATP + 2 NADH Ox. CO2 2 acetaldehyde (Box) 2 NAD+ 2 ethanol Applications: • Wine • Beer • Vodka • Bread

  15. 2 NAD+ 2NADH 2NADH 2 NAD+ 2 NAD+ 2 NAD+ 2 NAD+ 2NADH 2NADH 2 NAD+ 2 NADH Mixed acid fermentation Bacteria: • E. coli; Salmonella; Shigella, etc. Three (3) processes in the cell: 1) glucose  2 pyruvate  2 lactic acid 2 ATP ethanol CO2 + H2 2) glucose  2 pyruvate  CH3-CO~SCoA + HCOOH 2 ATP acetic acid + ATP CH3-CO~SCoA + formic acid (1) 3) glucose  2 pyruvate succinate (1) 2 ATP

  16. Mixed acid fermentation, cont. Applications: • Diagnose of pathogenic bacteria (clinical bacteriology) • Analysis of water in swimming pools etc.

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