Oxidative phosphorylation Flashcards
what does oxidative phosphorylation do
forms ATP through transfering electrons form NADH & FADH2 to O2 by electron carriers
What is the electron motive force (EMF)
high electron trasfer potential from the electrons attached to NADH and FADH2
How is the EMF harnessed
the electron transport chain
How the ETC harness EMF
transfers protons out of the mitochondrial matrix, through the IMM, and into the intermembrane space
WHat does the ETC harnessing EMF create
electrochemical gradient and a proton motive force (PMF)
what is the purpose of PMF
used by ATP synthase to generate ATP
Where is the ETC located
IMM
What is the IMM impermeable to
small molecules and ions
What is permeable to small molecules and ions
OMM
Why is the OMM leaky
it contains many pores
What is considered similar to the cytosol
IMS
What does cristae do
the many folds that increase surface area and allow many ETCs to be present
How can electrons be transferred
- free electrons (ETC)
- H- atoms (FADH2)
- H- hydride ion (NADH)
what does the standard reductive potential (E0’) measure
how likely a molecule is to accept electrons
WHat is a higher E0’
higher affinity to e-
Complex I of ETC
NADH - Q oxidoreductase
Where does complex I accept electrons from
NADH (accepts 2e-)
How to electrons move through complex I
FMN –> 4Fe –> 4S -> Coenzyme Q -> reuced to QH2 (ubiquinol)
How many protons are pumped by complex I
4
Complex II of ETC
Succinate Q reductase
Complex II Conversions
- succinate -> fumarate
- FAD -> FADH2
- Q -> QH2
Where does complex II get its electrons from
FADH2 from Krebbs
What is special about complex II
it is not a proton pump
why is complex II not a proton pump
electrons from FADH2 do not move as many H+ as NADH across the membrane
What moves e- from complex I and II to complex III
Co-enzyme Q
What is Co-enzyme Q also known as
Ubiquinone/Ubiquinol
Difference between Ubiquinone and Ubiquinol
Ubiquinone (Q) is fully oxidized
Ubiquinol (QH2) is fully reduced (i.e. contains the alcohols)
What does Coenzyme Q contain (hint: some kind of tail)
isoprenoid tail –> repeats 10x
How does Ubiquinone reduce to Ubiquinol
it accepts 2e- amd 2H+
Complex III
Q-Cytochrome C oxidoreductase
what is a cytochrome
an electron transferring chain containing one or more heme group
how many electrons to cytochromes carry
1
what cytochromes does complex III contain
cyt b & cyt c
WHere does Complex III take electrons from
QH2
Complex III electron flow process
Tkaes from QH2, oxidizes back to Q, transfers electrson ONE AT A TIME to 2Fe-wS cluster, then to heme C, then to heme c in cyt c
what cycle does complex III take place in
Q cycle
What is the Q cycle
process of transfering e- from ubiquinol to cytochrome C
What does cytochrome b do
moves e- into a ‘holding’ pattern
What is cytochrome C
electron shuttle that contains heme c
Heme C
water soluble protein that carries 1e- from complex III to complex IV
where is cyt c
sits on surface of IMM
how does cytochrome C move
free –> can move from complex to complex
shape of cyt C
spherical
how many H+ does complex III pump
4 (2 from matrix, 2 from Qh2)
Complex IV
Cytochrome C oxidase
What does Cytochrome C oxidase do
carries out final reduction
What is the final reduction
O2 to water
where does the final reduction get it’s e- from
cyt C
what 2 cytochromes does cCytochrome C oxidase contain
cyt a & cyta3
What copper centers does Cytochrome C oxidase contain
CuA & CuB
How to electrons flow through Cytochrome C oxidase
heme c -> CuA -> heme A -> hemea3/CuB
How many electrons are required to reduce O2 to 2H20
4
How many H+ are moved into the IMS by Cytochrome C oxidase
4
what does Cytochrome C oxidase prevent
release of partially reduced O2
how many protons does 2e- from NADH pump
10
how many protons does 1e- from FADH2 pump
6
What does ATP synthase do
harness the PMF created by the ETC to generate ATP
What are the 2 components of ATP Synathase
F1 and F0
WHere is F0
embedded in the IMM
What does F0 contain
1/2 channels that protons flow through
WHere is F1
extends into matrix from F0
What does F1 do
synthesizes ATP when coupled to the spin generated when protons flow through F0
What is F1 made up of
3 alpha-beta subunits arranged in a ball
What is in the center of the alpha-beta ball
gamma shaft
Does the F1 subunit rotate?
THe alpha-beta ball is stationary, but gamma subunit rotates
What is the property of
What is the property of the gamma shaft?
It is asymmetric -> so it binds to each fo the alpha-beta subunits differently
What are the 3 different alpha beta subunit sites
1) loose site (L) -> binds ADP + Pi
2) TIght Site (T) -> synthesize ATP
3) Opener Site (O) -> release ATP
How does the gamma shaft spin
F0 uses the proton gradient
Does each alphabeta subunit remain constant?
No -> rotates between L,T,O conformation
what does a 120º roation of gamma shaft result in
the release of 1 ATP into the matrix
What is a P:O value
number of ATP 2e- can generate
P:O value for NADH
2.5 ATP/NADH
P:O value for FADH2
1.5 ATP/FADH2
What is F0 composed of
subunit a and subunit c
F0: what is subunit c composed of
2 alpha helicies that span the membrane
how many subunit c’s are there in F0
9-12 arrnaged into the cylinder
what is the key resideu in subunit c alpha helicies
asparate/aspartic acid
what is subunit a known as
clamp
what does subunit a do
covers 2 c subunits
What does subunit a contain
2 half channels:
1) open to intermembrane psace
2) open to matrix
does subunit a or c rotate?
Subunit c rotates
subunit a is stationary
When can subunit c move into the membrane
1) if it is uncharged
2) If it is covered by subunit a (masks charge from membrane)
What happens when [ATP]/([ADP][Pi]) is high
low ADP, O2 consumption drops
What happens when [ATP]/[ADP][Pi] is low
high ADP, O2 consumption increases
What is acceptor control
regulation of cellular respiration by the availability of ADP as a phosphate acceptor
what does 2,4 dinitlophenol do
uncouples the ETC and ATP synthase by carrying H+ across the IMM, reducing the H+ gradient
what does uncoupling cause
The ETC speeds up, but ATP synthase remains the same -> proton gradient collaposes and ATP syntehsis will stop
How do electrons on NADH in the cytosol get to the ETC
1) glycerol-3-phosphate shuttle
2) Asparate malate shuttle
where is the glycerol-3-phosphate shuttle
skeletal muscle and brain
where is the Asparate malate shuttle
liver, kidney. cardiac myocytes
What are the reactions that happen in the glycerol-3-phosphate shuttle (in order)
1) DHAP -> Glycerol 3- phosphate (via. cytosolic glycerol-3-phosphate dehydrogenase)
2) NADH -> NAD+
3) Glycerol-3-phosphate -> DHAP (via. IMM bound Glycerol-3-phosphate dehydrogenase)
4) FAD -> FADH2
5) Q -> QH2
what are the reactions that happen in the asparate malate shuttle (in order)
1) oxaloacetate -> malate
2) NADH -> NAD+
3) malate/alpha-ketoglutarate translocase
4) malate -> oxaloacetate
5) NAD -> NADH
6) oxaloacetate -> asaparate + alpha ketoglutarate ( via glutamate)
How are ATP and ADP transported across the IMM
ATP/ADP translocate
How does ATP/ADP translocate work
exchanges 1ATP in the matrix for one ADP in the cytosol
What is ATP/ADP translocate driven by
charge gradient created by PMF
How is Pi transported across the IMM
phosphate translocate
What is phosphate translocate driven by
PMF
how is pyruvate tranpsorted into the matrix
pyruvate translocase
