Mitochondrial e- Transport & ATP Synthesis Flashcards
Define oxidative phosphorylation.
The process in which ATP is formed as a result of transfer of e- from NADH/FADH2 to oxygen by a series of e- carriers.
Define the etc.
a specialised set of protein complexes & e- carriers.
Which is the only complex in the etc not to span the membrane (located on matric side only)?
Cytochrome c
Give the 2 highly mobile e- carriers that shuttle e-.
Q & cytochrome c.
Why do e- flow through the etc?
Each complex/carrier has a lower free energy than the preceding member, so e- flow spontaneously down the chain.
How do e- generate ATP?
e- motive force is converted into H+ motive force.
H+ motive force is converted into phosphoryl transfer potential.
Describe Complex I of the etc.
NADH-Q reductase
34 polypeptide chains
membrane spanning structure & long arm extending into matrix.
Give the prosthetic groups in Complex I of the etc.
flavin mononucleotide
iron-sulphur clusters
Describe the role of Complex I in the etc.
2e- transferred from NADH to FMN.
FMN reduced to FMNH2.
FMNH2 transfers 2e- to series of Fe-S clusters.
2e- transferred to coenzyme Q, reducing it to QH2.
4H+ are pumped from matrix during this process.
Describe Complex II of the etc.
Succinate Q-reductase
Bound to inner mitochondrial membrane
also takes part in citric acid cycle
Describe the role of Complex II in the etc.
FADH2 loses 2e- to coenzyme Q via Fe-S clusters.
does not pump H+ because less ATP from FADH” compared to NADH.
Describe Coenzyme of the etc.
Coenzyme Q.
ubiquinone
Why is Coenzyme Q known as a ubiquinone?
it is a ubiquitous quinone in all biological systems.
Describe the role of Coenzyme Q in the etc.
accepts 2e- from Complex I or II to become QH2 & transfer them to Complex III.
hydrophobic, rapidly diffuses within inner mit. membrane.
Describe the role of Complex III in the etc.
Catalyses the transfer of 2e- from QH2 for each e- transferred from QH2, 2H+ pass out of matrix & 1 is donated to Q. occurs twice (2e- from Complex I & II each) so overall 4H+ pumped from matrix.
Describe Complex III of the etc.
Q-cytochrome c oxidoreductase
homo-dimer with 11 distinct polypeptide chains.
Give the prosthetic groups in Complex III.
heme
Fe3+ <> Fe2+
Describe the 5th protein in the etc.
Cytochrome C.
small soluble protein with c-type heme
Describe the role of the 5th protein in the etc.
carries 1e- from Complex III to Complex IV.
Describe Complex IV of the etc.
Cytochrome c oxidase
13 polypeptide chains
Give the prosthetic groups in Complex IV.
-2 heme prosthetic groups Fe a^3+ & Fe a3^2+ -2 copper ions Cu B^1+ & Cu A^2+ -these are redox centres
Describe the role of Complex IV of the etc.
heme a3 & CuB is the site of reduction of oxygen > water
for every NADH that enters the chain, 2x cyt c transfer 2e- to oxygen.
Why are 2 NADH/FADH2 required to split one molecule of oxygen?
because 4H+ & 4e- are required.
How many of the complexes in the etc are proton pumps?
3 out of 5.
