Lecture 9

• Chemoheterotroph

  organisms that use organic carbon compounds as sources of both carbon and energy
• Saprophyte

  an organism that uses dead organic material for nutrients
• Parasite

  an organism that feeds off living organic matter
• Alternatives to glycolysis

  • Pentose phosphate pathway
  • Entner Doudoroff pathway
• Photosynthesis

  • Conversion of incident light into ATP
  • Two pathways: cyclic and non-cyclic
• Cellular respiration

  • Aerobic respiration: Krebs cycle
  • Anaerobic respiration: uses sulfate or nitrate
• Energy production from glucose

  • Respiration = aerobic process
  • Fermentation = anaerobic process
  • Reactions are mediated by enzymes
• Glycolysis: preparatory stage

  • enzymatic processing of glucose
  • glucose > glucose 6-phosphate > fructose 6-phosphate > fructose 1,6-diphosphate > split into DHAP and GP, both 3 carbon with 1 phosphate
  • costs 2 ATP molecules
• Entner-Doudoroff

  • glucose + ATP > glucose 6-phosphate + ADP + NAD > 6-phosphogluconic acid - H2O > 2-KETO-3-DEOXY-6-PHOSPHOGLUCONIC ACID
  • Splits into pyruvic acid and GP
• Fermentation

  • anaerobic conditions
  • pyruvate degraded to form organic end products such as ethanol
• Chemiosmosis

  • use electrons to generate proton gradient
  • allow protons to flow across membrane
  • use ATPase running backwards to generate ATP
  • happens in alpha proteobacteria
• Proton motive force

  • goal: to create a proton gradient
  • protons pumped across membrane coupled to oxidation of carriers (NADH, NADPH, FADH2)
  • protons flow through F1F2 ATPase
  • 2 or 3 H+ = 1 ATP
• Escherichia coli electron transport

  • uses NADH, FADH2
  • uses 5 cytochromes: different depending on Po2
  • terminal electron acceptor: oxygen
  • 1.3 ATP per oxygen
• Paracoccus denitrificans electron transport

  • can grow heterotrophically or autotrophically
  • autotrophy: uses H2, CO2, NO2
  • NO2: TEA anaerobically, reduced to N2
• P/O ratio

  efficiency of aerobic respiration

  ATP produced per O2
• Uncouplers (ionophore)


  inhibit coupling between electron transport and phosphorylation reactions, inhibiting ATP synthesis