Bmsc 210 Mid1 p6

  1. Essentials of Catabolism
    • • Glycolysis
    • • Respiration and Electron Carriers
    • • The Proton Motive Force
    • • The Citric Acid Cycle
    • • Catabolic Diversity
  2. Fermentation:
    • substrate-level phosphorylation;
    • -ATP directly synthesized from Energy-rich phosphate bonds in phosphorylated organic intermediates
    • -Fermented substance is both an electron donor and an electron acceptor
    • • Relatively little energy yield
    • • Redox balance is achieved by production of fermentation products
  3. Respiration:
    • oxidative phosphorylation; ATP produced from proton motive force formed by transport of electrons
    • • Exogenous electron acceptors are present to accept electrons generated from the oxidation ofelectron donors
  4. Glycolysis (Embden-Meyerhof pathway):
    • Image Upload 1
    • a common pathway for catabolism of glucose
    • – Anaerobic process
    • – Fermentation: pyruvate is reduced by NADH to lactate to create 2NAD+
    • • Some harnessed by humans for consumption
  5. phosphorylation of glucose
    • first step in glycolosis
    • enzyme: hexokinase
    • couple reaction with ATP
    • products:ADP+G6P
    • ATP+Glucose->ADP+G6P
  6. Aerobic Respiration
    • – Oxidation using O2 as the terminal electronacceptor
    • – Higher ATP yield than fermentations
    • • ATP produced at the expense of the protonmotive force, which is generated by electrontransport
  7. _____ ATP produced from Glucose through Aerobic respiration. 
  8. Electron Transport Systems
    • – Membrane associated
    • – Mediate transfer of electrons
    • – Conserve some of the energy released during transfer and use it to synthesize ATP
    • – Many oxidation–reduction enzymes are involved in electron transport (e.g., NADH dehydrogenases, flavoproteins, iron–sulfur proteins, cytochromes)
  9. nomenclature for Catabolism
    • chemo vs photo (energy)
    • organo vs litho (whats being oxidized)
    • hetero vs auto (carbon source)
  10. Anaplerotic
    pathways used for both catabalism and anabalism
  11. NADH dehydrogenases
    • -proteins bound to inside surface of cytoplasmic membrane;
    • -active site binds NADH and accepts 2 electrons and 2 protons that are passed to flavoproteins
  12. Flavoproteins:
    contains flavin prosthetic group (e.g., FMN, FAD) that accepts 2 electrons and 2 protons but only donates the electrons to the next protein in the chain. Protons move to outside of membrane-pmf (Figure 4.15)
  13. Cytochromes
    • – Proteins that contain heme prosthetic groups(Figure 4.16)
    • – Accept and donate a single electron via the iron atom in heme
  14. Iron–Sulfur (FeS) Proteins
    • – Contain clusters of iron and sulfur (Figure 4.17)
    • • Example: ferredoxin
    • – Reduction potentials vary depending on number and position of Fe and S atoms
    • – Carry electrons in FeS prosthetic group
  15. Quinones
    • – Hydrophobic non-protein-containing molecules that participate in electron transport (Figure 4.18)
    • – Accept electrons and protons but pass along electrons only.Protons are moved outside the membrane-pmf
  16. The Proton Motive Force
    • • Electron transport system oriented in cytoplasmic membrane so that electrons are separated from protons (Figure 4.19)
    • • Electron carriers arranged in membrane in order of their reduction potential
    • • The final carrier in the chain donates the electrons to the terminal electron acceptor
    • • During electron transfer, several protons are released on outside of the membrane
    • – Protons originate from NADH and the dissociation of water
    • • Results in generation of pH gradient and an electrochemical potential across the membrane (the proton motive force)
  17. Through pmf the inside of the cell becomes electrically ____tive and pH becomes _____
    • negative
    • alkaline
  18. Through pmf the outside of the cell becomes electrically ____ive and pH becomes _____
    • positive
    • acidic
  19. ATP synthase (ATPase):
    • complex that converts proton motive force into ATP; two components(Figure 4.20)
    • – F1
    • – Fo
    • – Reversible; dissipates proton motive force
  20. F1 Component of ATPase
    multiprotein extramembrane complex, faces cytoplasm converts adp and Pi to ATP
  21. Fo Component of ATPase
    proton-conducting intramembrane channel
  22. Carbon fixation
    • reduction of inorganic carbon to organic compunds by living organisms
    • -photosynthesis
  23. Citric acid cycle (CAC):
    • pathway through which pyruvate is completely oxidized to CO2 (Figure 4.21a)
    • -Function however is to create reducing power- NADH
    • – Initial steps (glucose to pyruvate) same as glycolysis
    • – Plays a key role in catabolism and biosynthesis
  24. Product of Citric acid cylce Per glucose molecule
    6 CO2 molecules released and 8NADH and 2FADH 2GTP(ATP equivalent) generated
  25. Hetero fermentation products
    • 1st level: CO2, pyruvate and acetyl phosphate
    • 2nd level: CO2, Ethanol, and Lactate
  26. Image Upload 2-Ketoglutarate and oxalacetate (OAA):
    • precursors of several amino acids; OAA also converted to phosphoenolpyruvate, a precursor of glucose
    • -product of citric acid cycle
  27. Succinyl-CoA:
    • required for synthesis of cytochromes, chlorophyll, and other tetrapyrrole compounds
    • -product of citric acid cycle
  28. Acetyl-CoA:
    • necessary for fatty acid biosynthesis
    • -product of citric acid cycle
  29. Products of Citric acid cycle
    • Ketoglutarate and oxalacetate (OAA):
    • Succinyl-CoA
    • Acetyl-CoA
  30. mechanisms for generating energy
    • – Fermentation
    • – Aerobic respiration
    • – Anaerobic respiration
    • – Chemolithotrophy
    • – Phototrophy
  31. Anaerobic Respiration
    • – The use of electron acceptors other thanoxygen
    • • Examples include nitrate (NO3-), ferric iron(Fe3+), sulfate (SO42-), carbonate (CO32-),certain organic compounds
    • – Less energy released compared to aerobicrespiration
    • – Dependent on electron transport, generationof a proton motive force, and ATPase activity
  32. Chemolithotrophy
    • – Uses inorganic chemicals as electron donors. Less reduction power
    • • Examples include hydrogen sulfide (H2S), hydrogen gas (H2), ferrous iron (Fe2+), ammonia (NH3)
    • – Typically aerobic
    • – Begins with oxidation of inorganic electron donor
    • – Uses electron transport chain and proton motive force
    • – Autotrophic; uses CO2 as carbon source
  33. Chemolithotrophs
    organisms that obtain energy from the oxidation of inorganiccompounds
  34. Mixotrophs
    are chemolithotrophs that require organic carbon as a carbon source
  35. reduced compounds
    • • Many sources of reduced molecules exist inthe environment
    • • The oxidation of different reduced compoundsyields varying amounts of energy
  36. Iron Oxidation
    • • Ferrous iron (Fe2+) oxidized to ferric iron(Fe3+)
    • • Ferric hydroxide precipitates in water
    • • Many Fe oxidizers can grow at pH < 1 – Often associated with acidic pollution from coal mining activities (Figure 13.23)
    • • Some anoxygenic phototrophs can oxidize Fe2+ anaerobically using Fe2+ as an electron donor for CO2 reduction
    • • Ferrous iron oxidation begins with an outermembrane cytochrome c oxidizing Fe2+ to Fe3+, passing the electrons to rusticyanin in the periplasm (Figure 13.24)
    • • Rusticyanin then reduces a cytochrome c in the inner membrane, and this subsequently reduces cytochrome a
    • • Cytochrome a interacts with O2 to form H2O
    • -electron reduces NADto NADH
    • • ATP is synthesized from ATPases in the membrane
    • NADH+CO2+ATP->organic material

    • Autotrophy in Acidithiobacillus ferrooxidans is driven by the Calvin cycle
  37. Phototrophy:
    uses light as energy source
  38. Photophosphorylation:
    light-mediated ATPsynthesis
  39. Photoautotrophs:
    use ATP for assimilation of CO2 for biosynthesis
  40. Photoheterotrophs:
    use ATP for assimilation of organic carbon for biosynthesis
  41. Photosynthesis
    • is the conversion of light energy tochemical energy
    • – Carried out by phototrophs(Figure 13.1)
    • – Most phototrophs are also autotrophs
    • • Photosynthesis requires light-sensitive pigments called chlorophylls
    • • Photoautotrophy requires ATP production and CO2 reduction
  42. Oxygenic Photosynthesis
    • • Oxygenic phototrophs use light to generate ATPand NADPH
    • • The two light reactions are called photosystem I and photosystem II
    • • “Z scheme” of photosynthesis (Figure 13.18) – Photosystem II transfers energy to photosystem I
    • • ATP can also be produced by cyclicphotophosphorylation
  43. cyclicphotophosphorylation
    • -ATP can also be produced only using photosystem 1 by energizing electrons with photons and dropping down through a chain creating pmf.
    • -electrons are energized again instead of being given to Nad
  44. Z scheme
    -electrons are boosted by photons and dropped twice creating proton motive force
Card Set
Bmsc 210 Mid1 p6
Bmsc 210 Mid1 p6