1. Announcements
Now is the time to master quiz game and get highest score.
I specifically designed levels to help you practice these concepts
You can do each level over and over until you understand every answer
Honestly, I cannot possibly tell you how much you really really ought to do this.
I expect you to have mastered this stuff for the exam after thanksgiving, and I will write all the questions from this perspective

2. Today’s goal: Finish central metabolism in chemoorganoheterotroph
Glucose
Glycolysis
Pyruvate
Citric acid
Cycle
ATP
NAD+
H2O
NADH
ETS
ATP synthase

3. The TCA cycle (citric acid or Krebs cycle)

4. Principles of oxidative phosphorylation

5. Learning outcomes
Be able to calculate the free energy of a reaction based on the change in reduction potential
Be able to identify potential electron donors and acceptors for metabolism based on reduction potential
Apply understanding of reduction potential to determine how electron transfer releases energy in oxidative phosphorylation
Explain the elements of proton-motive force and how it powers the ATP synthase and flagella
Be able to compare and contrast oxidative phosphorylation and substrate-level phosphorylation
Use redox potential to make predictions about how and why oxidative phosphorylation varies, resulting in alternative metabolisms and acclimation to the environment.
Compare and contrast aerobic and anaerobic respiration

6. Reduction potential
Fundamental concept affecting everything else you learn today and Thursday.

7. Reduction potential and relationship to ∆G
E = Potential to accept electrons
Eo = in standard conditions
Eo’ = standard plus pH 7
∆E = E of acceptor –E of donor
∆Go’ = -nF∆Eo’
n = moles of electrons
Faraday’s constant = 96.5 kJ/Vmol

8. Example:complete oxidation of glucose
Between two redox couples:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
What is the electron donor?
What is the electron acceptor?
Redox couple:

9. We can find E in a redox tower
Capacity to donate
Capacity to accept

10. ∆E and ∆G for complete oxidation of glucose
Between two redox couples:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
∆Eo’ = E(acceptor) – E(donor)
= (O2/H2O) ([CH2O]/CO2)
∆Go’ = -nF∆Eo’
n = moles of electrons
Faraday’s constant = 96.5 kJ/Vmol
∆G = kJ/mol

11. We can use the redox tower as a cheat sheet
∆Go’ = -nF∆Eo’
For negative ∆G
∆E should be + or- ?
Down the tower or up the tower?
In an endergonic reaction, should E increase or decrease?
Capacity to donate
Capacity to accept

12. A series of redox reactions in cell Membrane generates proton-motive force
How the reservoir above the dam gets filled up with water….

13. Electron carrier molecules do redox rxns

14. Arrange carriers in order to get -deltaG
NADH Eo’ = -320mV
O2 Eo’ = +820 mV
Ubiquinone Eo’ = +110mV
FMN Eo’ = -190 mV
FeS cluster Eo’ = mV
Cytochrome c Eo’ = +250 mV

15. Series of oxid/reduction reactions ensues
NADH O2
STEAM >>> STEAM train

16. Electron carriers are arranged in proteins

17. Energy release from rxns fuels proton pumps
Oxidoreductase:
Protein complexes where oxidation/reduction reactions occur
Buckets thrown over the reservoir

18. Quinone pool: Electron transfer and pmf
Protons come from cytoplasm

19. Proton-motive force generation in E. coli

20. Microbes can change composition of their ETS
To modulate their physiology depending on environment. They have preferred ratio of +/- across membrane.
Example: acidic environment

21. What proton-motive force is and how it drives ATP synthesis
What is in the reservoir, and how that potential energy is converted into ATP

22. Potential energy → mechanical → ATP

23. Proton-motive force Denoted ∆p
Includes: ∆pH and ∆ψ (electrical potential)
The force exerted by the reservoir

24. ATP synthase: potential energy >> mechanical

25. How PMF runs bacteria flagella

26. What is the 3rd function of PMF in bacteria?
Follow-up: Then why might the cell want to use ATP to run ATP synthase backwards?

27. Anaerobic respiration
What it is
E of terminal acceptor structures communities
Variation in e-donors and acceptors determines G for anaerobes
Anaerobes may not use NADH

28. Anaerobic respiration
Electron acceptors other than oxygen
Examples include:
SO4 Mn Fe
NO3
NO2
Uranium, Plutonium, Tc99

29. ETS complexes vary with donors/acceptors

30. Analyzing respiration
1. Nature of the acceptor: What is the acceptor reduced to? How many reduction steps occur?
2. What is the electron donor? It’s role in central metabolism? What molecule starts the Electron transport system (ETS)?
3. How does the ETS differ depending on 1 and 2? How many protons pumped? How does this relate to delta G?

31. Example anaerobic respiration: nitrate
∆Go’ = -nF∆Eo’
How many steps does each acceptor take?
Which molecule donates electrons to ETS?
Which transfers more electrons?
Which has biggest change in reduction potential?
Donor = C6H12O6
Pseudomonas
NO3- – NO2- – NO – ½ N2O – ½ N mV
Donor = C6H12O6
E. coli
NO3- – NO mV
Based on above, what do you expect?
How does the ETS differ depending on 1 and 2? How many protons pumped? How does this relate to delta G?

32. Nitrate reduction (denitrification)
Do these images match what you might expect? Why or why not?
E.coli with oxygen
E.coli, no oxygen but nitrate
Pseudomonas

33. Example: sulfate respiration
If they catabolize lactate – are they likely to use NADH?
E for lactate = mV
E for NADH = -320mV
Lactate → Pyruvate
electrons ?
NADH
How are electrons donated to the ETS? ?
ETS?

34. Hint: hydrogen accumulates
Is hydrogen involved?

35. Central metabolism layout, sulfate reducers

36. Electron donor, acceptor, predictions
1. Nature of the acceptor: What is the acceptor reduced to? How many reduction steps occur?
2. What is the electron donor? It’s role in central metabolism? What molecule starts the Electron transport system (ETS)?
3. How does the ETS differ depending on 1 and 2? How many protons pumped? How does this relate to delta G?

37. Abbreviated model of sulfate reduction
Hydrogenase (H2ase):
Enzyme splits hydrogen into protons and electrons

38. This is real life: Just FYI
Model for the respiratory chain of D. vulgaris during growth on hydrogen, or lactate, and sulfate.
Hydrogenases
Formate dehydrogenases
Cytochromes
Fe-S proteins
Cytochromes
Hydrogenases
Venceslau S S et al. J. Biol. Chem. 2010;285:
©2010 by American Society for Biochemistry and Molecular Biology

39. What is oxidative phosphorylation?