Lecture 17 & 18 : e- transpoprt chain

Question 1

what is general process of e- transport chain

Answer 1

1. NADH ubiquinone oxidoreductase (e- from nadh captured here)
2. succinate ubiquinone oxidoreductase (e- from fadh2 captured here)
3. e- from both given to UBIQUINONE (Q) to form UBIQUINOL (QH2)
4. these transfered to cytochrome c reductase complex
5. which transfers to cytochrom c
6. then to cyt C oxidase complex
7. which transfers e- to O2 to make H20

Question 2

why do the e- pass through these complexes in this order

Answer 2

free energy decreases as you go down
thermodynamiclaly favourable

Question 3

what does ubiquinone turn into when it reduced with e-

Answer 3

is reduced 1 e- at a time
- first from ubiquinone to semiquinone (radical)
- then to ubiquinol (or CoQH2 or dihydroquinone)

Question 4

when e- pass through succinate Q oxidoreductase, are protons transferred

Answer 4

not into intermemb space, so it DOESNT contribute to proton gradient
instead, the 2H+ from fadh2 go to Q to make QH2

Question 5

how are e- transferred from QH2 to cytochrom C via ubiquionol cytochrom C reductase (complex III)

Answer 5

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

Question 6

what is complex IV cytochrome oxidase responsible for

Answer 6

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

Question 7

equation for the formation of H2O by complex Iv

Answer 7

O2 + 4e- + 6H (matrix) –> 2H2O + 2H+

Question 8

what is the 2 components of the ATP synthase molecule

Answer 8

F1 = knob = catalytic subunits
F0 = stalk = proton channel

Question 9

how many ~H+ needed for 1 ATP molecule

Answer 9

3 for ATP synthase
1 for transport of Pi across membrane
so 4 overall

Question 10

what are the subunits of F1

Answer 10

• 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

Question 11

what does each beta subunit hold

Answer 11

active site for ATP synthesis

Question 12

what are the 3 conformations the beta subunit can exist in

Answer 12

open
loose
tight

Question 13

what does the open state do

Answer 13

binds ADP + Pi

Question 14

what does the loose state do

Answer 14

active site closes loosley on ADP + Pi

Question 15

what does tight state do

Answer 15

converts ADP + Pi to ATP

Question 16

what drives the conformational changes of all these B subunits

Answer 16

flow of protons which causes the rotation

Question 17

what provides direct evidence for rotational motion of ATP synthase

Answer 17

binded actin filament to immobilised head of ATP synthase
fed it ATP + H2O which made it rotate in the opposite direction

Question 18

how does ATP and ADP get across the inner mt membrane (and Pi too)

Answer 18

adenine nucleotide translocase (ANT)
allows antiport of ATP for ADP
- Pi enters through symport with H+

Question 19

what is a P:O ratio

Answer 19

ADP phosphorylated/atoms of oxygen reduced

Question 20

how did we get the numbers of 2.5 ATP from NADH and 1.5 from FADH2

Answer 20

NADH allows 10H+ to be transported in e transport chain = 2.5 ATP
FADH2 allows 6H+ to be transported = 1.5 ATP