BIOL2210 ETC and ATP synth

which memb contains ETC

inner mito memb

are ETC components ordered from most negative to postitive or positive to negative in their standard reduction potential

most negative to postitive

what molecules are good electron donors

mols with most negative standard reduction potential

which complexes translocate protons and how many

CI 4

CIII 4

CIV 2

what carrier goes between complexes I II and III

ubiquinone

what carrier goes between complexes III and IV

cytochrome C

what are some of the redox active molecules in the ETC (in/associated with complexes)

flavins, Iron sulfur (FeS) centres/clusters, quinones, cytochromes, haems, copper centres

what type of carriers are flavins quinones

hydrogen atom carriers (H+ and e-)

how many hydrogens atoms can flavins carry

2

(gain them in 2 steps)

what type of carriers are Iron-Sulfur (FeS) centres/clusters

electron carriers

how many electrons can cytochrome c carry at one time

1

structure of complex 1 (NADH-Q oxidoreductase)

1 MDa

14 central and 30 peripheral subunits (some mito encoded)

role of complex 1 and

oxidise NADH and FADH2 to yield reduced Ubiquinone

name of complex 1

NADH-Q oxidoreductase

name of complex II

succinate dehydrogenase

what redox mol/centre does the electron pass via in complex II from FADH2 to ubiquinone

FeS centre

result of succinate oxidation by complex II

yields FADH2 which reduces FeS centre that reduces ubiquinone

what enables ubiquinone to readily move between complex I II and III

lipophilic nature (due to long aliphatic chain) allows it to readily move thru lipid bilayer

structure of cytochromes

redox active iron surrounded by porphyrin ring linked to protein

how do types of cytochromes (cyt a b c) differ

by nature of side chains of porphyrin ring and linkage to protein

types of linkage in cyt c vs a and b

cyt c has covalent (thioester) bond to protein

cyt a and b have non covalent linkage

name of complex III

Q-cytochrome C oxidoreductase

what redox mols/centres does complex III have

FeS centre, Cytochrome c and b, ubiquinone

name of cycle that CIII is involved in

(proton motive) Q cycle

how does the FeS centre of CIII differ to normal FeS centres

has more positive charge than normal, making it a better electron centre (has 2 his and 2 cysteine residues in it, not just 4 cysteines, that stabilise reduced form)

proton motive Q cycle

Qo site on CIII where QH2 binds, and 2 e go diff ways

1 transf to cyt C via Reiske FeS centre, Cyt C1

1 transf to 2nd ox Q at Qi site via Cyt bL and bH

what happens to the H+ from the oxidised QH2 at complex III

released into cytosol

what happens at Qi site of CIII

recieves 1 e per QH2 (so 2 cycles) and takes up 2 H+ from matrix therefore is reduced to QH2

products from 2 QH2 mols at CIII

2 red cyt c

1 QH2

which complex has copper centres

CIV

what centres does CIV have

copper centre Cu a and Cu b, haem a and a3

what happens at CIV

red cyt C reduces Cu A site then pass e to Haem a, haem a3, Cu b

next e same way to Fe of haem a3

O2 binds Fe and forms peroxide bridge between a3 and Cu b

e from next cyt c reduces peroxide bridge with H+ from matrix

next e reduces Fe with another H+

Then gain of 2H+ results in rel of H2O

how many protons are taken up from the matrix by CIV

and how many pumped per O2 reduced (form 2 H2O)

4 taken up (chemical protons)

4 pumped (pumped protons)

(4 e used)

chemical protons vs pumped protons

protons used in chem reaction (H2O formation) vs just pumped

purpose of the Q cycle of CIII

solution to problem of getting ubiquinone, carrying 2 hydrogen atoms, to interact with type b cytochromes which carry a single e

what is an uncoupler

provides route for H+ back thru memb so ETC can continue without ATP synthesis

structure of CV (ATP synthase)

F1 - 3 a and 3 b subuints (regulatory and catalytic)

gamma subunit (connects F1 and F0)

F0 ring of Hphobic mols that act as H+ channel

where is the c subunit ring part of in ATP synthase

F0

role of 3 b subunits in F1 of ATP synthase

catalytic subunit (site of ATP synth)

what does protons flowing thru F0 cause

rotation of c ring, that driving rotation of gamma subunit, driving conf change in a and b subunits of F1

structure and function of gamma subunit

connects F1 and F0

asymmetric so differential contact with each b subunit of F1 causing sequential conf change

how many ATP mols are made per 360o rotation of ATP synthase F0/gamma

3

does F1 of ATP synthase rotate

No

name of mechanism involving conf change in a and b subunits resulting in ATP synth

binding change mechanism

what is P:O ratio

how many molecules of ATP can be made per O atom reduced to H20

how many H+ does each c subunit of F0 translocate per rotation

1

how many c subunits does ATP synthase have in vertabrates

8

how many H+ are required to produce one ATP in vertabrates

8/3 = 2.7 but 1 H+ req for transp ADP + Pi into mito since their transp is linked to H+ grad

so 3.7 H+ per ATP

what is P:O ratio in vertabrates for 2 e from NADH linked substrates and FADH2 linked substrates

10H+/3.7 = 2.7

6H+/3.7 = 1.6

how would a higher number of c subunits affect the P:O ratio

more c subunits results in lower P:O ratio

seen in bact, yeast, chloroplast