Lecture 17 & 18 : e- transpoprt chain Flashcards
what is general process of e- transport chain
- NADH ubiquinone oxidoreductase (e- from nadh captured here)
- succinate ubiquinone oxidoreductase (e- from fadh2 captured here)
- e- from both given to UBIQUINONE (Q) to form UBIQUINOL (QH2)
- these transfered to cytochrome c reductase complex
- which transfers to cytochrom c
- then to cyt C oxidase complex
- which transfers e- to O2 to make H20
why do the e- pass through these complexes in this order
free energy decreases as you go down
thermodynamiclaly favourable
what does ubiquinone turn into when it reduced with e-
is reduced 1 e- at a time
- first from ubiquinone to semiquinone (radical)
- then to ubiquinol (or CoQH2 or dihydroquinone)
when e- pass through succinate Q oxidoreductase, are protons transferred
not into intermemb space, so it DOESNT contribute to proton gradient
instead, the 2H+ from fadh2 go to Q to make QH2
how are e- transferred from QH2 to cytochrom C via ubiquionol cytochrom C reductase (complex III)
1 at a time (1 QH2 to 2 CytC)
cyt c has a Fe3+ grou that can carry 1 e- at a time
and in the process 4H+ and transported into int memb
what is complex IV cytochrome oxidase responsible for
recieves e- from cytrochrome C one at a time
and catalyses reaction of O2 to H2O (passes the e- it gains to O2)
and 2 more H+ are translocated
equation for the formation of H2O by complex Iv
O2 + 4e- + 6H (matrix) –> 2H2O + 2H+
what is the 2 components of the ATP synthase molecule
F1 = knob = catalytic subunits
F0 = stalk = proton channel
how many ~H+ needed for 1 ATP molecule
3 for ATP synthase
1 for transport of Pi across membrane
so 4 overall
what are the subunits of F1
- has 3 alpha and beta subunits that make up the round knob bit
- 1 gamma and epsilon = make the central axle between the knob and stalk
- 1 delta which is on outside of the knob
what does each beta subunit hold
active site for ATP synthesis
what are the 3 conformations the beta subunit can exist in
open
loose
tight
what does the open state do
binds ADP + Pi
what does the loose state do
active site closes loosley on ADP + Pi
what does tight state do
converts ADP + Pi to ATP
what drives the conformational changes of all these B subunits
flow of protons which causes the rotation
what provides direct evidence for rotational motion of ATP synthase
binded actin filament to immobilised head of ATP synthase
fed it ATP + H2O which made it rotate in the opposite direction
how does ATP and ADP get across the inner mt membrane (and Pi too)
adenine nucleotide translocase (ANT)
allows antiport of ATP for ADP
- Pi enters through symport with H+
what is a P:O ratio
ADP phosphorylated/atoms of oxygen reduced
how did we get the numbers of 2.5 ATP from NADH and 1.5 from FADH2
NADH allows 10H+ to be transported in e transport chain = 2.5 ATP
FADH2 allows 6H+ to be transported = 1.5 ATP
