Oxidative Phosphorylation Flashcards
1) 3 ways of describing oxidation reactions
- add O2 directly to the molecule
- remove an electron
- remove a pair of H atoms
2) Which part of Nicotinamide Adenine Dinucleotide is involved in oxidation and reduction?
Nicotinamide ring
3) Which part of Flavin Adenine Dinucleotide is involved in oxidation and reduction?
Flavin groups
4) Where does oxidative phosphorylation take place and what is its function?
- In mitochondria of most tissues and cell types (not RBCs)
- ‘Energy trapping’ –> direct phosphorylation ADP –> ATP
5) Where are the cytochrome components found?
- Buried in the inner membrane of mitochondria
6) What are the 2 hydrogen pair acceptors?
- Flavin cofactors (FAD)
- Coenzyme Q / CoQ/ Ubiquinone
7) What are the 2 electron acceptors?
- Iron sulfur proteins (cysteine on outside, can convert between Fe2+ and Fe3+)
- Cytochrome proteins (Haem ring is electron acceptor)
8) Define oxido-reduction potential/ redox potential?
- Ability of carrier to donate its electrons to another electron acceptor molecule. Electrons move from carrier of more negative potential to carrier of more positive potential
9) What type of reaction occurs when electrons are passed on?
- exergonic reactions (-delta G)
10) State the order of oxidation/reduction carriers in the ETC.
- Flavin > CoQ > cytochrome b > cytochrome c > cytochrome a
11) What are the redox values of NAD/NADH, FAD/FADH2 and O2/H2O?
NAD/NADH: -0.32V
FAD/FADH2: -0.20V
O2/H2O: +0.82V
12) The transfer of protons creates which two gradients across the membrane?
- Concentration gradient (pH gradient)
- Voltage gradient (membrane potential)
13) Describe the waterwheel analogy of ATP Synthase.
- Flow of water is H+ ions, wheel is ATP Synthase and movement/flow causes ATP production (rotational energy)
14) Which reaction is necessary to reoxidise FADH2 to FAD for binding to ubiquinone in the ETC?
- (TCA Cycle) Succinate to Fumarate with succinate hydrogenase enzyme, in the inner membrane, as this produces FADH2 which can then be oxidised to FAD and bind to ubiquinone
15) ATP yield of oxidative phosphorylation?
- NADH reoxidised = 2.5 ATP
- FADH2 = 1.5 ATP
= 4 ATP
16) How does ATP and ADP concentrations affect the rate of O2 uptake? (described as respiratory control or ‘tightly-coupled’ oxidative phosphorylation)
- High [ADP] = higher rate of O2 uptake
- High [ATP] = lower rate of O2 uptake
17) Name the 3 inhibitors of oxidative phosphorylation and their action
- CN- and CO inhibit cytochromes
- Rotenone inhibits Coenzyme Q
18) Define uncoupling agent
- Provides easier route for H+ to return to matrix, from intermembrane space (bypassing ATP synthase so energy produced is used as heat rather than for phosphorylation)
19) Name 2 uncouplers of oxidative phosphorylation.
- Dinitrophenol (DNP)
- Thermogenin protein (present in brown adipose tissue)
20) Total ATP yield for 1 molecule of glucose
- 30/32 ATP
21) Where are the complexes involved in maintaining the proton gradient of the respiratory chain located in the mitochondria and what are their functions?
- Located in cristae
- Complex I : NADH/ubiquinone reductase - feeds e- from NADH into the respiratory chain, transfers to CoQ
- Complex III : cytochrome C reductase - accepts e- from CoQ and transfers them to small, soluble e- carrier protein cytochrome c
- Complex IV : cytochrome C oxidase - transfers e- from cytochrome c to molecular oxygen
22) Which complex is not involved in maintaining the proton gradient and what is its function?
- Complex II : succinate dehydrogenase -transfers e- from succinate directly to CoQ and does not contribute to proton gradient
