Oxidative Phosphorylation 1 Flashcards
What is oxidative phosphorylation
the electrons in NADH and FADH2 from TCA
transported down the electron transport chain via oxidation reduction reactions
Where does the ETC happen
In the mitochondrial memebrane
How many protien complexes are in the ETC
4 (I-IV)
What are the elections carriers/“taxis” in the etc
Ubiquinone (Q)
Cyctochrome C
Where do electrons come from in the etc
NADH or FADH2
What is the final electron acceptor in the ETC
oxygen which turns into H2O
As electrons flow from NADH and FADH2 to Oxyegn in the ETC, what is the delta G
-220
Highly exergonic
What is the symbol for redox potential
E^’•
What is used as a reference in measuring redox potential
Which way do electrons flow
Hydrogen
From the sample to the standard half cell
What does it mean when you have a negative reduction potential
The oxidized substance has a lower affinity for electrons than the H2 reference
The easier it is for the element to be oxidized
If the reaction is flipped so that the sample is getting reduced and the standard is getting oxidized what happens
Ie, electrons are flowing in the opposite direction
The reduction potential flips and becomes positive
What does postivtice reduction potential mean
It means that the oxidized substance that lost electrons has a higher affinity for elections than the standard hydrogen electrode
(Would rather be reduced)
Does oxygen have a positive or negative reduction potential
What does this mean
Has a postive reduction potential,
It’s better at being reduced and taking in electrons
Does NAD+ have a negative or positive reduction potential?
What does this mean
Negative
This means that it is better at being oxidized and giving up electrons
Would rather stay in the from it’s in
How to calc delta g
Slide 11
What happens in the first part of the electrons transport chain
Nadh in the matrix transfers electrons to complex 1
While it does this, FADH2 transfers electrons to complex 11
Why does FADH first transfer electrons to complex 11 instead of complex one like Nadh
It has a less negative reduction potential than Nadh
Meaning it’s not as good at being oxidized as NAHD
What oxidizing agent is present in all four complexes in the ETC and in cytochrome c
Why
Iron as a prosthetic group
It has a positive reduction potential so it’s good at being reduced and oxidizing NADH and FADH2
What does the reduction potential of iron depend on?
What does iron appear as in the etc
Is depends on the environment surrounding it
As Iron Sulfur Clusters
In addition to iron, what else is in
Complex 4 of the etc?
What is another name for complex 4
Copper (gets reduced)
cytochrome c oxidase
What is coenzyme Q in the ETC
It is ubiquinone and it moves electrons from complex one and 2 to complex 3
What is the properties of coenzyme Q
It’s a ubiquitous quinone
It has isoprene units which are just hydrophobic tails
It shuttles both electrons and protons through the ETC
Which complexes in the ETC pump protons
How does it do this
1 3 and 4
Because the reaction is exergonic
Why are protons not pumped out complex 2
Since fadh2 doesn’t interact with complex one, less protons are pumped out
What is the proposed model of how protons are pumped out of complex one in the ETC
Q (ubiquinone) binds to complex one in a deep channel
Through the iron sulfur clusters, electrons flow from NADH to ubiquinone
The membrane arm moves protons from lys/glu residues to Q2- to make QH2
A change in the structure happens where QH2 leaves and protons get taken up and a total of 4 protons is released by NuoL in the membrane
What makes the 4 protons in NuoL get ejected in complex 1
Electrostatic pressure
How does complex 11 in TCA work
What is it called
The succinate Q reductase complex
Succinate dehydrogenase from TCA is part of this complex
FADH2 is a prosthetic group of this complex which gets oxidized and reduced ubiquinone to make QH2 (ubiquinol)
What are the electron carriers in complex 11 of the ETC
Fad+, iron sulphur protiens, coenzyme Q
How does complex three of TCA work and what is it named
Cytochrome c reductase/Q-cytochrome c oxidoreductase
The pervious ubiquinol (QH2) move from complex 1 and 11 to complex 111
At complex 111, it gives up 2 electron but cytochrome C (electron taxi) take 1
How many electrons have cytochrome C accept
1 electron
What subunits are invoked in the complex 111 structure
Cytochrome c which has a heme subunit
Cytochrome BL and Bh
Iron sulfur groups
How is the problem of cytochrome c only taking one electron fixed
The Q cycle
What is the Q cycle first half
When QH2 bind to complex 111, two protons a released to the IMS (inter membrane space)
Cyt C gets one electron and move to complex 4
the other electron moves from cyt B to Q to make a Q•- radicle
Then this oxidized Q radical moves off of complex 111
What is the Q cycle second half
A second QH2 bind to complex 111
Two protons from it are moved to IMS
One e moves to cyt c again and is move to complex four again
The other is moved through cyt B to the Q radical and two hydrogen from the IMM turn it into QH2
What happens in complex 4 what is it called
Cytochrome c oxidase
After cyt c gets an electron, it moves to complex 4 to get reduced and give up its electrons
2 moclecules of cyt c bind and transfer two electrons to the fe and Cu prosthetic groups of the complex
The reduced prosthetic group bind to o2 and make a PEROXIDE BRIDGE
Two more cyt c bind again and 2e and 2H from the matrix cleave the bridge and make OH on either side
2 H from the IMM go to this broken bridge and release 2 H2O from it
2H2O goes to the imm
In complex four where do all of the hydrogen in the reaction come from
Not the IMS, from the IMM
Per one reaction in complex 4 (4 cyt c reductions) how much protons are use up
How much is sent to the IMS
4 protons from the IMM are used up
But 4 are also sent to the IMS
In complex three how many protons are move to the IMS
4
What are the ETC oragsinzed into and how does this help
Into a respirasome
This improved the efficiency and moves the substrate and electrons from one complex to the next
