c430 Electron Transport Chain
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1. What types of physiological structures have a lot mitochondria?
2. Who is mit DNA from? What is special about it?
3. How does its structure dictate its function? (2)
- 1. Structures that require a lot of energy
- 2. Mother - it's a self-contained cell.
- 3. Invaginations --> large esurface area (cristae) allow lots of proteins to be embedded.
1. What is the greatest source of electrons for ETC?
2.What are differences between FMN and FAD?
3. What is the role of Complex II?
- 1. NADH
- 2. FMN doesn't have FAD's AMP moiety
- 3. Complex II transfers electrons from FADH2 (succinate dehydrogenase) to Coenzyme Q (but doesn't pump any electrons(
Describe mechanism of Complex I (4)
- 1. NADH binds to Complex I (contains FMN)
- 2. NADH transfers 2 e-s to FMN (--> FMNH2), lowering activation barrier
- 3. FMNH2 passes e-s one by one to CoQ (through series of iron-sulfur clusters)
- FMNH2 has stable radical state.
- 4. Complex I simultaneously pumps 4 protons to intermembrane space.
1. Why aren't H+ pumped out from Complex II from FADH2?
1. B/c standard reduction potential of FADH2 is only slightly less than that of CoQ --> no H+ are pumped out.
Describe mechanism of Complex III (6)
Describe Mechanism of complex IV (8)
1. For each molecule of O reduced, how many protons are transferred from matrix to IM space for NADH? for FADH2?
2. How many matrix protons are used to build 2 waters from O?
3. How is free energy released by redox steps stored?
4. How are protons transferred back to matrix? via what mechanism? What is their role?
1. 20, 12
3. Stored in proton gradient produced
4. all of them via ATP synthase to indirectly drive ATP synthesis by changing B-conformations in F1
1. Where is ATP synthase found?
2. What is the function of ATP synthase?
3. What drives the production of ATP?
4. What Is another word for ATP synthase?
5. What are the two distinct components of ATP synthase and where are they found?
- 1. Embedded in inner mitochondrial membrane
- 2. To catalyze formation of ATP from ADP + Pi (w help from proton-motive force)
- 3. Proton motive force
- 4. Complex V
- 5. F1 (peripheral membrane protein) and Fo (part of membrane)
1. What happens if you don't have F1?
2. On the enzyme surface what is the free energy change for ATP + Pi --> ATP + H2O?
3. Why does ATP synthase favor ATP production?
1. System can still catalyze e- transfer from NADH to O2, but can't produce proton gradient --> can't make ATP.
2. dG = 0 (freely reversible)
3. Despite dG = 0, ATP binds to ATP synthase at higher affinity tahn ADP --> binding energy releases enough energy to drive eq towards formation of ATP
1. What is the purpose of the proton gradient? (2)
2. What is the purpose of F0? Of F1?
3.How does the energy reaction profile of ATP synthesis to for from the energy profile of other reactions?
4. How many different confirmations does each Beta subunit at ATP synthase have? What are they?
5. What is crucial to the mechanism of the complex?
1. (1) Driving force for ATP synthesis (2) Promotes release of ATP (despite high binding affinity to ATP synthase)
2. F0 is where H+ enters and it spins around, F1 catalyzes ATP synthesis
3. In most rxns, formation of product is hard part. In ATP synthesis, releasing ATP is the hard part.
4. 3: B-empty, B-ADP, and B-ATP
5. The difference in nucleotide binding of the three different B subunit conformations!
1. What is the key to binding-change mechanism for ATP synthesis?
2. What is the underlying basic theory?
3. Describe mechanism (5)
1. Rotational catalysis
2. The 3 active sites of F1 take turns catalyzing ATP synthesis
3. 1. A given Beta unit begins in beta-ADP confirmation binding ADP and Pi from surrounding medium
2. This subunit changes conformation into B-ATP form (tightly binding & stabilizes ATP)
3. Then turns into B-empty (low affinity for ATP)
4. ATP leaves
5. Unit changes from B-empty to B-ADP form and starts again.
1. What drives the conformational changes of the beta subunits in F1? Describe in detail
2. How do B-subunits interact to decide conformation?
3. What does each 360 degree rotation cause? (2)
4. What happens when ATP synthase is doing ATP hydrolysis?
1. Streaming protons through Fo pore cause cylinder of subunits to rotate along gamma's axis.
With each rotation of 120degrees, gamma comes into contact w/ a different B subunit, forcing conformational change in B-empty conformation.
2. B-subunits interact in such a way that if one assumes empty B-empty conformation, one neighbor must be B-ADP and the other B-ATP
3. Synthesis & release of 3 ATP
4. It spins the opposite way of ATP synthesis
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