MMT: oxidative phosphorylation Flashcards
Define oxidative phosphorylation.
Process in which ATP is formed from the transfer of electrons from NADH and FADH2 to O2 by a series of electron carriers
Identify the initial electron donors and terminal electron acceptor of the electron transport chain
Initial: NAD+ and FAD+
Terminal: oxygen
complex I of the ETC: what it takes its electrons from, how many protons it pumps, and how it works
- NADH
- 4 protons
- Contains iron-sulfur clusters that bind to cysteine residues in the protein. FMN first accepts the electrons from NADH, and then transfers them onto iron-sulfate clusters. A molecule of CoQ gets reduced to CoQH2 by the electrons
complex II of the ETC: what it takes its electrons from, how many protons it pumps, and how it works
- FADH2
- 0 (it does not span the membrane!)
- donates electrons from FADH2 to CoQ. also forms fumarate from succinate.
complex III of the ETC: what it takes its electrons from, how many protons it pumps, and how it works
- CoQH2
- 4 protons
- it donates electrons from CoQH2 to cytochrome c.
describe the electron transfer from CoQH2 to cytochrome c
CoQH2 carries two electrons, by cytochrome C can only accept one. Thus, it uses the Q cycle to fix this. One electron bounces through iron-sulfur cluster, cytochrome C1 unit, and then to cytochrome C. this electron can immediately go to complex IV. the other electron comes through cytochrome b electron node and finds a separate CoQ molecule sitting in complex III. It waits for another cycle to receive a second electron to become CoQH2, when can then go and re-enter the cycle
Describe complex IV of the ETC: what it takes its electrons from, how many protons it pumps, and how it works
- cytochrome c
- 2 protons
- donates electrons to oxygen to form water
Relate myocardial infarction induced cardiac cell death to oxidative phosphorylation.
The decreased oxygen supply impacts our ability to form ATP. In the ETC. ATP is needed for cellular processes and energy, causing the cells to dysfunction and damage. This is a huge issue.
How does the structure of the mitochondria allow for the proton gradient to form?
The outer mitochondrial membrane is permeable to protons due to VDACs, while the inner membrane is largely impermeable. This allows for a proton gradient along the surface (cytosolic side) of the inner mitochondrial membrane.
Identify the energetic link between oxidation in the electron transport chain and ATP
generation
A proton motive force
What are E’ and G’
E’: electron transfer potential, also known as the reduction potential or redox potential
G’: phosphoryl transfer potential
As we move through the ETC, we move from ___ to ___ reduction potential, and ___ to ___ free energy
Negative to positive; higher to lower
We gain energy as we go!
Compare and contrast Coenzyme Q and Cytochrome C
- Cytochrome c is water soluble and moves in the intermembrane space of the mitochondria. it contains a heme covalently linked to the protein by 2 cysteine residues.
- CoQ is a mobile electron carrier that shuttles between complexes I and II and complex III. it is not bound to protein and is hydrophobic.
explain the transfer of electrons through Complex IV: cytochrome c oxidase.
-Two cytochrome C molecules enter. 2 electrons bounce from a copperA center to heme a, to heme a3, and to copperB. The first molecule will reduce the CuB, and the second will reduce the heme a3.
-The reduced centers form a peroxide bridge by accepting an oxygen molecule
-Two more electrons cytochrome C molecules enter. This allows two more electrons to enter the cycle and break the peroxide bridge. Two protons are used to stabilize the oxygen to form hydroxyl groups.
-Two more protons are pulled in to form water that can dissociate and leave
Describe the mechanism of cyanide toxicity.
Cyanide can bind to heme a3, which blocks complex IV and shuts down the ETC. if we cannot reduce water we cannot accept electrons. TCA will then shut down and we rely on glycolysis, and our tissues cannot be sustained off of glycolysis only. We die pretty fast.
