Oxidative phosphorylation Flashcards
what is oxidative phosphorylation?
where ATP formed as result of e- transfer from NADH or FADH2 to O2 by e- carriers
mitochondria in eukaryotes
cytoplasmic membrane in bacteria
generates 26/30 molecules of ATP
mitochondrial structure
cristae impermeable to protons
gradient across membrane
respiratory proteins bounds within inner membrane of mitochondria
how are the mitochondrial mechanically complex?
proton complexes in inner mitochondrial membrane
pumping H+ out of mitochondrial matrix
uneven distribution creates pH gradient & transmembrane electrical potential
proton motive force
what is proton motive force used for?
to drive ATP synthesis
how does oxidative phosphorylation work?
energy converted to different forms is always conserved
e- motive force converted to H+ motive force
proton motive force converted to phosphorylation transfer potential
just changing different forms of energy
what are the e- driven proton pumps
NADH-Q oxioreductase
Q-cytochrome c oxioreductase
cytochrome c oxidase
where are the redox centres?
quinones
flavins
iron-sulphur clusters
hemes
copper ions
large transmembrane complexes that contain multiple redox centres
coupled transmembrane movement
oxidation andATP synthesis are coupled b transmembrane proton movement
process of e- transfer causes pump of protons
what is the first e- carrier in the respiratory chain?
NADH-Q oxioreductase
takes e- from NADH and transfers them to Q
what is NADH-Q oxioreductase?
structure consists of a membrane spanning part and long arm that extends into the matrix
NADH oxidised in the arm
e- transfered to reduced Q in the membrane
huge and very complex
half sits within membrane half outside
what is the mechanism of NADH-Q oxioreductase
NADH + Q + 5H+ —> NAD+ +QH2 + 4H+
what is the function of NADH-Q oxioreductase
transfer of 2e- from NADH to FMN
e- fro FMNH2 are transferred to series Fe-S clusters
e- from Fe-S clusters shuttles to Coenzyme Q
Q is reduced
what is Q?
coenzyme
comes from NADH and FADH2
hydrophobic
diffuses rapidly within inner mitochondrial membrane
3 oxidation states
what are the e- carriers in the respiratory chain?
succinate dehydrogenase
uses FADH2 as e- donor
what is succinate dehydrogenase?
membrane protein of inner mitochondrial membrane
e- from FADH2 transferred to Fe-S clusters then to Q
doesn’t pump protons
less ATP formed by oxidation of FADH2 than NADH
what I the second e- carrier in the respiratory chain?
Q-cytochrome c oxioreductase
what is Q-cytochrome c oxioreductase
homo-dimer with 11 distinct polypeptide chains
3 heheh and a 2Fe-2S cluster
taking e- from Q and transferring them to cytochrome c
what is the mechanism of Q-cytochrome c oxioreductase?
QH2 + 2Cytcox + 2H+matrix —> Q + 2Cytcred + 4H+cytosol
what is the function of Q-cytochrome c oxioreductase?
catalyses transfer of e- from QH2 ro oxidised cytochrome
pumps protons out of mitochondrial matrix
what is cytochrome c?
small soluble protein containing c-type heme
carries one e- from Q-cytochrome c oxioreductase to cytochrome c oxidase
reaction takes place twice
what I the third e- carrier in the respiratory chain?
cytochrome c oxidase
what is cytochrome c oxidase?
enzyme that has 13 polypeptide chains
prosthetic groups are:
Cua/ Cua
heme a
heme a3-cub
- heme a3-cub is site of reduction of oxygen to water
have multiple redox cofactors, copper and dinucleotide centre
what I the mechanism of cytochrome c oxidase?
4Cytcred + 8H+matrix + O2 —> 4Cytcox + 2H2O + 4H+cytosol
4 chemical protons taken from matrix side to reduce one molecule of O2 to 2xH2O
4 pumped protons transported out of the matrix & released on cytosolic side in the course of reaction
pumped protons
double efficiency of free energy storage in the form of a proton gradient
end of e- transfer
what is atp synthase?
contains F1 subunits and Fo subunit
what is the F1 subunit?
catalytic unit
5 types of polypeptide chains
a & b subunits makeup bulk
central stalk consists of 2 proteins
what is the F0 subunit?
proton conducting unit
hydrophobic segment
spans inner mitochondrial membrane
contains proton channel of the complex
10c subunits and a subunit
what is the mechanism of ATP synthase?
ADP3- + HPO4 2- + H+ <—> ATP4- + H2O
readily forms in absence of a proton motive force
ATP doesn’t leave catalytic site unless protons flow through enzyme
role of proton gradient is to release it from ATP synthase
need gradient for ATP to leave active site of the substrate
can only spin using proton motive force
Inhibition of oxidative phosphorylation?
e- transport chain can be inhibited at various stages
coupling of e- transport and op disrupted by DNP
allows protons to flow back across membrane without going through ATP synthase
what in an uncoupling protein?
in hibernating animals uncoupling of oxidative phosphorylation is a way of generating heat without synthesis of ATP