Microbial Metabolism Lecture

Key Topics

• Microbial metabolism
• Energy production and utilization in cells
• Carbon sources and cycles
• Metabolic pathways: Catabolism and Anabolism
• Cellular respiration
• Aerobic vs. Anaerobic respiration
• Glucose metabolism pathways

Microbial Metabolism

• Definition: Generation and utilization of energy in cells (prokaryotic and eukaryotic).
• Organisms and Carbon:
  • Autotrophs: Use carbon dioxide from the atmosphere; engage in photosynthesis to produce glucose using sunlight.
  • Heterotrophs: Rely on glucose from other organisms; cannot use atmospheric carbon dioxide directly.
• Carbon Cycle: Autotrophs and heterotrophs depend on each other for carbon dioxide and oxygen exchange.

Metabolism

• Definition: Sum of all chemical transformations in a cell or organism.
• Types of Metabolism:
  • Catabolism: Breakdown of nutrients into simpler molecules; releases energy.
  • Anabolism: Synthesis of complex molecules from simpler ones; requires energy.
• Cellular Respiration: Production of ATP, essential for energy metabolism.

Types of Respiration

• Aerobic Respiration:
  • Requires oxygen; final electron acceptor is oxygen.
  • Produces more ATP.
• Anaerobic Respiration:
  • Occurs without oxygen; final electron acceptor is a non-oxygen inorganic molecule.
  • Less efficient in ATP production.

Glucose Metabolism

• Glucose is a crucial energy molecule, often referred to as a currency molecule.
• Fates of Glucose:
  • Stored as glycogen in animals or starch in plants.
  • Oxidized to pyruvate (glycolysis).
  • Used in pentose phosphate pathway to produce nucleic acids.

Metabolic Pathways

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

Fermentation

• Occurs in the absence of oxygen.
• In yeast, glucose is fermented to ethanol.
• Produces less ATP compared to aerobic respiration.

Practical Examples and Questions

• Aerobic respiration is the most efficient at producing ATP.
• Anaerobic bacteria can live in human tissues not exposed to oxygen, e.g., the bladder.
• Aerobic bacteria infect tissues exposed to oxygen, e.g., the respiratory tract.
• Electron transport chain in eukaryotic cells occurs in the mitochondria.

Conclusion

• Understanding microbial metabolism is crucial for understanding energy production and utilization in various organisms.