Chapter 20 (Complexes) Flashcards
Complex I
NADH Dehydrogenase
Electron transfer from NADH to the mobile protein CoQ
Redox centers are: FMN and Fe-S clusters
Four H+ transported out per 2e-
___ bridges the gap between NADH (only 2e- at a time) and Fe (only 1e- at a time)
FMN
Overall equation for Complex I
NADH + H + CoQ (goes to) NAD + CoQH2
Highly exergonic
Complex I has enough energy to synthesis ___ when e- come back in
ATP
-81 kJ/mol
Complex II
Succinate Dehydrogenase
Oxidation of FADH2 by CoQ
Only e- from ___ can enter into Complex II
Succinate
Overall equation for Complex II
Succinate + CoQ (goes to) Fumarate + CoQH2
Only slightly exergonic so NO H+ is pumped into the matrix during this step
Complex II (does/does not) contribute to the proton gradient
does not (not enough Delta G knot)
___ can only enter via Complex I
Matrix NADH
Regardless of where an e- enters (either Complex I or II) it will always end up in the ___
UQ/UQH2 pool
Before the e- enter Complex III the only Complex that translocates protons (H+) up till this point is Complex ___
I
Complex III
CoQ-Cytochrome c Oxidoreductase
Passes e- from reduced CoQ to cytochrome c (carries only 1e- at a time)
Complex III
CoQ-Cytochrome c Oxidoreductase
Passes e- from reduced CoQ to cytochrome c (carries only 1e- at a time)
In Complex III the oxidation of one ___ is accompanied by the translocation of ___ H+ across the ___ membrane
UQH2
4
inner mitochondrial
In Complex III the oxidation of one ___ is accompanied by the translocation of ___ H+ across the ___ membrane
UQH2
4
inner mitochondrial
UQ-
semiquinone form
UQ-
semiquinone form
The Qp site in Complex III is located closer to the ___
intermembrane space
The Qp site in Complex III is located closer to the ___
intermembrane space
Complex IV
Cytochrome c Oxidase
Cytochrome c drops off 1e- and oxidzes 1/2O2 into H2O
utilizes 2 hemes and 2 Cu sites
linear electron transfer
The Qn site in Complex III is located closer to the ___
Matrix
The Q cycle takes place in Complex ___
III
First half of Q cycle
UQH2 leaves the pool and donates 1e- to cytochrome c in the Qp site (resulting in the translocation of 2 H+) and becomes UQ-
UQ- last e- goes to the Qn site (resulting in UQ which goes back into pool)
A UQ from the pool enters the Qn site and takes the 1e- that came from the Qp site (resulting in a UQ-
Second half of Q cycle
UQH2 leaves the pool and donates 1e- to cytochrome c in the Qp site (resulting in the translocation of 2 H+) and becomes UQ-
UQ- last e- goes to the Qn site (resulting in UQ which goes back into pool)
The UQ- from the first half take the 1e- that came from the Qp site as well as 2H+ from the matrix and becomes UQH2 (which then enters back into the pool)
Formal name for Complex IV
Cytochrome c Oxidase
___ is the terminal acceptor of e- in the ETC pathway
Oxygen
The complete reduction of O2 requires ___ e-
4
Complex IV transports ___ H+ for every 1e-
1
Complex IV uses ___ radicals, so if the complex is “leaky” this will result in:
super oxide
damage to the cells
Mitochondrial NADH proton transfers through: I II III IV
I: 4H+ II: (isn't used) III: 4H+ IV: 2H+ Total of 10H+
Succinate (FADH2) proton transfers through: I II III IV
I: (isn't used) II: (no protons transfered) III: 4H+ IV: 2H+ Total of 6H+
___can only enter via Flavoprotein 4
Cytosolic NADH (via Glycerol Phosphate Pathway)
The FAD in Complex ___ is covalently attached to a ___
II
His residue
