L3-Microbial Metabolism: Energetics, Enzymes, and Redox

• Metabolism


  The series of biochemical reactions needed to sustain life, including catabolism (energy release and molecule breakdown) and anabolism (material synthesis)
• Fundamental metabolic requirements of all cells

  • Water
  • Carbon sources
  • Nutrients
  • Free energy
  • Reducing power
• Exergonic reactions


  Chemical reactions that release energy as they proceed
• Endergonic reactions


  Chemical reactions that require an input of energy to proceed
• Catabolic pathways


  Exergonic processes that generate free energy by transforming reactants into products
• Anabolic pathways


  Endergonic processes that require an input of energy for the synthesis of cellular material from simple precursors

  
• Reducing power


  The ability to donate electrons during electron transfer (redox) reactions
• Metabolic classes of microorganisms based on energy source

  • Phototrophs (obtain energy from light)
  • Chemotrophs (obtain energy from chemical reactions)
  • Chemoorganotrophs (obtain energy and reducing power from organic molecules)
  • Chemolithotrophs (obtain energy and reducing power from inorganic molecules)

  
• Redox reaction


  A reaction involving simultaneous oxidation and reduction
• Reduction potential


  A measure of a compound's tendency to acquire electrons and be reduced, measured in Volts (V)
• Electron carriers


  Soluble molecules like NAD+/NADH that carry electrons from one location to another within the cell
• ATP


  The energy-carrying molecule found in the cells of all living things, not a storage molecule
• Cellular energy conservation via ATP


  1. ATP is synthesized from ADP and phosphate through cellular respiration

  2. ATP powers cellular processes by transferring a phosphate group to another molecule (phosphorylation)

  3. Most ATP is produced by the enzyme ATP synthase in the mitochondrial membrane
• Enzymes


  • Biological catalysts, typically proteins, that accelerate chemical reactions by lowering the activation energy required
  • Have an active site where the substrate(s) bind and catalysis occurs
  • Act on specific substrate molecules
  • May require cofactors or coenzymes to function properly
  • Exhibit high specificity, often following a "lock-and-key" model
  • Activity is influenced by temperature and pH, and can be regulated through feedback inhibition

  
• Enzyme naming


  • Enzymes are usually named systematically, often ending in "-ase" and reflecting the substrate and type of reaction catalyzed (e.g. lipase acts on lipids)
• Enzymes play a crucial role in various biotechnological processes, including the production of pharmaceuticals, food processing, and molecular biology techniques
• Next week's lecture overview will cover catabolism, glycolysis, citric acid cycle, glyoxylate cycle, and fermentation