Oxidative Phosphorylation Flashcards
What is the Malate-Aspartate shuttle and why is it necessary? What are the roles of malate dehydrogenase and aminotransferases in the shuttle?
- e- transferred from NADH to oxaloacetate -> forms malate
- malate crosses membrane
- e- transfer to NAD+ -> forms NADH
- NADH passes e- to ETC via Complex I
malate dehydrogenase: catalyzes conversion btw malate and oxaloacetate
How is energy produced by aerobic respiration? What is consumed? Why do electrons flow from NADH to O2 as opposed to the reverse direction?
- 1 mol of glucose converted to 2 mol of pyruvate -> generates ATP
- 2 ATP consumed
- Moves from least to most reduction potential (willingness to accept e-)
What is the function of the hemes and iron sulfur complexes in the ETC ?
Transport e- through ETC complexes
Mobile electron carriers
CoQ (ubiquinone) and cyt C (cytochrome C)
Where does coenzyme Q fit into the ETC? What are the reductions states of Q? What paths bring electrons to reduce QH2?
- present in Complexes I, II, III
- oxidized -> reduced
- Complex III brings e- to reduce QH2
Why and how does FADH2 lead to fewer ATPs generated than NADH? What pathways bring electrons in via FADH2?
FADH2 activates fewer proton pumps in ETC
Glycerol 3-phosphate shuttle -> Complex II of ETC
What is the point of the “Q Cycle” in complex III? How many electrons can QH2 carry, and why doesn’t it just hand off all of them at once to Cytochrome C?
Complex III needs 2 cytochromes reduced to successfully transfer 2 e- from CoQ, only 1 e- transferred per e- transfer from ion (why not all at once)
How is proton movement across a membrane coupled to ATP synthesis?
Coupled formation of ATP (endergonic) + e- transport (exergonic)
Proton-motive force - decr pH and incr voltage differences contribute to changes in electrochemical gradient which stores energy used to form ATP
What are the main components of the F1-F0 ATPase and how do each contribute to the synthesis of ATP? How is ATP made? What drives this process?
F0 forcibly rotates the γ-subunit in the clockwise direction and then F1 catalyses the reverse reaction
ATP synthesized by counterclockwise rotation
Driven by forced coupling of ADP and Pi
What is the role of the gamma subunit and how does its interactions with the Alpha/Beta Subunits contribute to catalysis?
Gamma = rotary motor inside the cylinder formed by the alpha/beta subunits in the F1 complex
How would you generate an acidic compartment in the cell, such as inside lysosomes?
Proton pump that uses proton-motive force (decr pH in membrane)
Uncoupler
Molecule that inhibits the coupling between the electron transport and phosphorylation reactions -> inhibits ATP synthesis
How do hydrophobic proton carriers such as DNP and FCCP interfere with ATP production?
Uncouples ATP synthesis from proton gradient, stops production
Thermogenin
Uncoupling protein that speeds up ETC, produces thermal energy (heat) rather than ATP b/c collapses proton gradient and uncouples ETC from ATP synthesis
