Microbial Metabolism

• Metabolism


  The sum of all chemical reactions that occur in a cell
• Catabolism


  Energy-releasing metabolic reactions- breakdown of complex molecules into simpler molecules, and harvesting their energy in the form of ATP

  
• Anabolism


  Building of complex molecules from simpler molecules
• Energy acquired in catabolism is used in anabolism
• Types of metabolism based on carbon source

  • Autotrophs
  • Heterotrophs

  
• Types of metabolism based on energy source

  • Chemotrophs
  • Phototrophs

  
• Chemotrophs


  Use chemical source of energy
• Organotrophs


  Use organic source as energy
• Lithotrophs


  Use inorganic source as energy
• Enzymes


  Biological catalysts, typically proteins (some RNAs), highly specific, have an active site that binds substrate
• Metabolic pathway


  Reactions that occur in a sequence, where the product of one reaction becomes the substrate of the next
• Components of a metabolic pathway

  • Initial reactant/substrate
  • Intermediates
  • End product
• Electron donor


  The substance oxidized in a redox reaction
• Electron acceptor


  The substance reduced in a redox reaction
• Redox tower


  • Represents the range of possible reduction potentials, substances toward the top (reduced) prefer to donate electrons, substances toward the bottom (oxidized) prefer to accept electrons, the farther the electrons "drop", the greater the amount of energy released

  
• NAD+ and NADH


  Facilitate redox reactions without being consumed, act as coenzymes carrying electrons from one reaction to another

  
• ATP


  High-energy compound used to drive metabolic reactions, not stored by cells but constantly being generated from ADP

  
• ATP cycle


  1. ADP + Phosphate -> ATP

  2. ATP -> ADP + Phosphate

  
• ATP has higher potential energy than ADP
• Phases of cellular respiration

  • Glycolysis
  • Preparatory (prep) reaction -> Breakdown of pyruvate
  • Citric acid cycle
  • Electron transport chain (ETC)

  
• Glycolysis


  Produces 2 ATP, 2 NADH

  
• Pyruvate breakdown


  Produces acetyl, CO2, NADH
• Citric acid cycle


  Produces 2 CO2, 1 ATP, 3 NADH, 1 FADH2 per acetyl
• Electron transport chain


  Extracts energy from NADH, FADH2 to power ATP synthase and generate ATP

  
• Aerobic cellular respiration can generate up to 34 ATP per glucose molecule
• Differences between aerobic respiration in eukaryotes and prokaryotes

  • Glycolysis location
  • Pyruvate breakdown location
  • Citric acid cycle location
  • Electron transport chain location

  
• Fermentation


  Metabolic process that converts carbohydrates to alcohols or organic acids, does not use an electron transport chain
• Types of fermentation


  • Alcoholic fermentation
  • Lactic acid fermentation
• Photosynthesis


  Conversion of light energy to chemical energy

  
• Types of phototrophs


  • Photoautotrophs
  • Photoheterotrophs
• Photoautotrophs


  Use energy from light to reduce CO2 to organic compounds
• Photoheterotrophs


  Phototrophs that use organic carbon as a carbon source
• Light reactions


  Produce ATP and NADPH in photosynthesis

  
• Dark reactions


  Reduce CO2 to cell material for growth in photosynthesis, require ATP and electrons (NADH or NADPH)

  
• Chlorophylls and bacteriochlorophylls


  Light-sensitive pigments that absorb light energy for photosynthesis
• Photosynthesis


  The conversion of light energy to chemical energy

  
• Phototrophs


  • Carry out photosynthesis
• Most phototrophs


  • Are also autotrophs that use CO2 as sole carbon source
• Photosynthesis


  1. Light reactions produce ATP and NADPH

  2. Dark reactions reduce CO2 to cell material for growth

  
• Light reactions


  Require ATP and electrons (NADH or NADPH)