Oxidative Phosphorylation Flashcards
Oxidative Phosphorylation (Oxphox)
The process in which energy in the form of e- is passed to electron carriers and used indirectly to form ATP
Oxidative phosphorylation example
Ox step:
NADH + H+ + o2 –> NAD+ + H2O
FADH2 + O2 –> FAD + H2O
Phos step:
ADP + Pi –> ATP
Where is acetyl CoA generated?
matrix of mitochondria
What is the Electron Transport Chain?
A series of protein complexes located at the inner membrane of the mitochondria
Where are the protein complexes of the ETC located?
Inner membrane of mitochondria
What are the protein complexes of ETC made of?
lipids and multiple proteins
Which protein complex of the ETC is in the TCA?
succinate dehydrogenase (Complex 2)
What is the purpose of the prosthetic groups in the protein complexes??
electron carriers - continue passing electrons
What are mobile electron carries?
List them.
Not tightly membrane bound. Can move around the inner mitochondrial membrane from one complex to the next
- NAD
- Coenzyme Q (ubiquinone - fully oxidized state)
- Cytochrome C
What are non-mobile elctron carriers
Prosthetic groups
Tihghly bound to enzyme
FAD
Fe-S centers
Hemes
What is Heme
found in cytochrome a, b1, c1
embedded in specific ETC protein complexes
can act as electon carrier, it foes from ferric (Fe3+, oxidized) to ferrous (Fe2+, reduced)
-FE is tightly bound, held by 4 nitrogens in porphyrin ring
not to be confuses with cytochrome C
What is unique about complex 1
-only pint where nadh give up electrons
NADH goes from reduced state to oxidized state and releases a H
What happens when elctrons travel from one carruer to the next
energy is created
so H pumped from matrix to intermembrane spcae
Where do the electrons from compelx 1 and 2 end
coenzyme q
becoems fully reduced in compelx 2
Whats the diffence bw compelx one and two
in comepelx 2elctrons does not create enoguh energy to push H
so there is no proton gradient here in complex 2
What is unique about complex 1
-only pint where fadh2 give up electrons
What is the e- collection site for compelx 1 and 2
COq
Who does coq give elctorns to and how?
compelx 3
Complex 3 has two binding sites for coq
one for fully reduced (ubiquinol)
one for fully oxidized (ubiquinone)
Why complex 3 has teo bindind sites
One site for coQ binding when it is fully reduced
and another site for CoQ. fully oxidized CoQ binding.
CoQ comes with 2 electrons but compelx 3 can collect 1 e at a time
For each QH2 oxidized, 4H+ are pumped to the intermembrane space
Explain the CoQ cycle
Look at yt vid for better explanation
Transfer of 2e- from QH2 to complex III must occur 1 e- at a time
complex 3 has 2 binding sites for CoQ
The fully reduced CoQ binds and one e- goes to cytochrome c
Cytochrome C can only acceot one e-
The coQ that gave the elctron is now a semiquinone free radical (it has 1 e-)
That remaining 1 e- will eventually go to the other CoQ that is fully oxidized’
Since it has now lost its 2 e-, it is now fully oxidized and it leaves the binding site (bc gthe binding site was for reduced coQ)
But now we have the other coQ that is now a semiquinine free radical. SQ can react with O2 and produce oxygen radicals
Another fully reduced CoQ comes in, same process is repeated (1 e- goes to cytochrome C and the other e- goes to the electon other carriers in comlex 3)it becomes fully reduced and leaves
semiquinone will capute e- coming from the electron carriers in compelx 3, then leave its site.
https://www.youtube.com/watch?v=h-r0OAReDKc
what is unique about compex 4
where o2 resides (final e- colector)
When o2 collects elctions, h being produces prodcues water
What is purpose of the proton gradient
used as energy to activate ATP synthatse where ADP can be covented to ATP
How H return to the matrix
throught the barrel part of the comppelx onthe ATPase
How does ATP leave the matrix
when one ATP leaves matrix, 1 ADP enters. This movement requires `1 H
ADP/ATP translocase carries the ATP.ADP in and out
Which molecules there are no translocators for
AND+, NADH
Coa, acetyl Co-a and acyl -Coa
oaxlacetate
tehy use another shuttle system and possibly change from one form to another then change back when it reaches its desired location
What is the outcome of inhibition of electron trasnport
elctron transfer is initated at compelx 1 and 2
if these two are inhibited, no electron transfer occurs and wont be any proton gradiaent buolsing up and imapcts synthesis ATP synthesis
ultimately, no flux of electorns affects proton gradient and no ATP being generated
What is meant by coupling of electron transfer and ATP synthesis
Electron transport requires ATP synthesis
ATP synthesis requires electron transport
If a person consumedachimcial that irreversible inhibited all cytochromesi nteh ETC:
- the amount of heat generated from NADH eould incrase
- Death would result from a lack of ATP
- The rate of succinate oxiadation wouldnot change
- An electrochemical gradient could still be generated
2
Transer of elctrns throgh hich of teh following elctrong trasnport chain compelxes doe not geneae enogh enery tp drive the synthesis of ATP
- Compelx 1
- complex 2
- complex 3
- complex 4
complex 2
What are the electron carriers of individual protein complexes called?
Prosthetic groups
What is the final electron acceptor?
Oxygen
What are Fe-S centers
- One electron carrier (even when 2> iron atoms mare present)
- coordination by cysteins in the protein
- containing equal number of iron and sulfur atoms
- Rieske Fe-S proteins (another confirmation) : 1 Fe is coordinated to two His instead of 2 Cys
- At least 8 Fe-S proteins function in mitochondrial ETC
O2 consumption and ATP synthesis
O2 consumption and ATP synthesisdepends on the presence of ADP + Pi and an oxidizable substrate
What happens if ADP is not available
succinate cant be oxidized
inhibits ATP synthesis, will inhibit e- trans to O2
