Lecture on Microbial Metabolism

Introduction to Microbial Metabolism

• Focus on the generation and utilization of energy in prokaryotic and eukaryotic cells.
• Organisms differ based on carbon utilization:
  • Autotrophs: Use photosynthesis, utilize CO2 from the atmosphere to produce glucose using sunlight.
  • Heterotrophs: Rely on organic molecules for carbon; cannot use atmospheric CO2 directly.
• Autotrophs and heterotrophs are interdependent:
  • Autotrophs use CO2 from heterotrophs to produce oxygen and glucose.
  • Global warming concerns due to deforestation affecting oxygen production.

Definitions and Key Concepts

• Metabolism: Sum of all chemical reactions in a cell/organism.
  • Driven by enzyme-catalyzed reactions forming metabolic pathways.
• Catabolism: Breakdown of organic molecules into simpler ones, releasing energy.
• Anabolism: Synthesis of complex molecules from simpler ones, requires energy.
• Cellular Respiration: Production of ATP, involves conversion between ATP and ADP.

Types of Respiration

• Aerobic Respiration:
  • Occurs in oxygen-rich environments; oxygen is the final electron acceptor.
• Anaerobic Respiration:
  • Occurs without oxygen; final electron acceptor is an inorganic molecule.

Glucose Metabolism

• Glucose is the primary energy molecule, important for both plants and animals.
• Pathways of Glucose:
  • Stored as glycogen (animals) or starch (plants).
  • Oxidized to pyruvate via glycolysis.
  • Further oxidized in the pentose phosphate pathway to produce nucleic acids.
• Terminology Clarifications:
  • Catabolism = Oxidation.
  • Anabolism = Reduction/Synthesis.

Glycolysis and Citric Acid Cycle

• Glycolysis: Converts glucose to pyruvate.
• Citric Acid Cycle (Krebs Cycle): Occurs in mitochondria (eukaryotes) or cytoplasm (prokaryotes).
• Oxidative Phosphorylation: Final stage producing ATP, occurs in mitochondria (eukaryotes) or plasma membrane (prokaryotes).

Anaerobic Metabolism

• Does not require oxygen.
• Produces lactic acid as a byproduct.
• In humans, lactic acid can be recycled by the liver.

ATP Production Pathways

• Photosynthesis: Requires photosynthetic pigments and light.
• Aerobic Respiration: Most efficient ATP production method.
• Anaerobic Respiration and Fermentation: Less efficient, but viable under certain conditions.

Practical Considerations

• Human Tissues and Bacteria:
  • Anaerobic bacteria in oxygen-poor environments, e.g., human bladder.
  • Aerobic bacteria in oxygen-rich environments, e.g., respiratory tract (pneumonia).
• Electron Transport Chain:
  • Occurs in mitochondria (eukaryotes) or plasma membrane (prokaryotes).

Conclusion

• Summary of microbial metabolism and its importance in energy production and ecosystem interdependencies.