electron transport and oxidative phosphorylation Flashcards
what does oxidative phosphorylation mean
the removal of electrons from metabolic intermediates and the synthesis of ATP from ADP
what processes can ATP help with
cofactor for signal transduction reaction using a variety of kinases
what is the cellular ATP concentration usually
1-10mmol/L
what is the total quantify of ATP in an adult
0.1mol/L
how many mols/l of atp is required daily
100 to 150 mol/L
how many times is an ATP molecule recycled
1000-1500 times per day
how much percentage of atp does the mitochindria make
more than 95% of ATP to support aerobic respiration
what processes is the mitochondria also involved in
intracellular signalling
intracellular calcium regulation
cellular differentiation and growth and cellular death pathways
what is located in the mitochondrial matrix
an independent mitochondrial genome
describe the mitochondria
the outer membrane- contains porins which allows for diffusion of ATP, ADP,CA,PHOSPHATE into the intermembrane space
the inner membrane- binds the matrix which is folded into cristae to increase the SA
how does OP begin
by electrons entering the respiratory chain
where do the electrons which are used in OP come from
the action of dehydrogenase from catabolic pathways- attached to NAD AND FAD
what is the equation for the breakdown of NADH
2NADH—> 2NAD+2H+ 4e-
what happens to the electrons that are released from NAD
high energy electrons are passed from one complex to another down an electron chain
what are the complexes arranged in
increasing potential and increasing electron affinity
how many complexes are there in the ETC
4
complex 1,2,3,4
what happens to the electrons when they reach complex 4
react with hydrogen and oxygen to form water
what happens as electrons move down the ETC
they release energy which allows hydrogen ions to be actively transported into the intermembrane space
how are the electron transporters arranged
organised into the membrane and embedded supramolecular complexes
where does NADH drop electrons in the ETC
complex 1
where does FADH drop electrons in the ETC
complex 2
what are the three electron carriers
ubiquinone
cytochrome c reductase
cytochrome c
what is the first electron carrier
flavin mononucleotide
what does flavin mononucleotide do
it oxidises NADH to NAD and becomes reduced by accepting electrons
what is the name of complex 1
NADH-Q oxidoreductase
what is the pathway of FMN becoming reduced
flavin mononucleotide semiquinone intermediate flavin mononucleotide (reduced)
what needs to happen to the electrons for the energy to be released
passed down a number of iron sulphate complexes
how is iron bound to sulphur
a single iron atom is tetrahedrally coordinated with 4 SH–Cys groups
what happens to the iron molecules in this reaction
they can switch between fe2+ and fe3+
which amino acid is Sulphur found in
cysteine
how does the electron transfer oxidation and reduction occur
by direct transfer
what is the third electron carrier
co enzyme Q/ubiquinone
what happens to the electrons after they are carried by the FE-S complex
they are carried by ubiquinone which can diffuse rapidly within the inter mitochondria membrane
describe ubiquinone
it is a hydrophobic quinone which can diffuse across the membrane
what is the pathway of ubiquinone reduction
ubiquinone(full oxidised)
semiquinone radical
ubiquinol ( fully reduced)
what are the two functions in complex 1
- the transfer to ubiquinone of a hydride ion from NADH and a proton from the matrix
- pumps four protons into the IMS
what is complex two called
succinate dehydrogenase-
what is different about succinate dehydrogenase
the only membrane bound enzyme in the citric acid cycle
what is contained into complex 2
three 2[Fe-S] centres
a bound FAD
and a binding site for the substrate succinate
what is the electron pathway in complex 2
succinate binding site to FAD FE-S FE-S FE-S Q
what is the name of complex 3
cytochrome bc1
what occurs in cytochrome bc1
couples the transfer of electrons from ubiquinol to cytochrome c with the transport of H+ from the IMS
what is the coupling of the electron transfer from ubiquinol and the transport of H+ called
the Q cycle
what is complex 4 called
cytochrome c oxidase
what is contained in complex 4
2 heme groups and 2 copper centres
what does the copper centre do in complex 4
accepts electrons from reduced cytochrome c and reduces the second copper centre
what is the pathway of the electron in complex 4
- first cooper centre accepts electrons from reduced cytochrome c and reduces the second copper centre
- electron transfer to Fe in heme a2
- both copper centre and iron in heme is in a reduced state
- the iron centre binds with oxygen and the bound oxygen forms peroxide from the transfer of 2 electrons
- the oxygen bridges the fe and cu- formation of the peroxide bridge
- the third cytochrome c dumps electron and cleaves the O-O bond and takes a proton
- the fourth cytochrome c dumps electrons and reduces the ferryl group
- an uptake of 2 protons allows for the release of 2H20
how is ATP produced in ATP synthase
chemiosmotic hypotheses
what enzyme synthesises ATP
ATP synthase
how does the chemiosmotic hypothesis work
as protons are pumped into the membrane space it is now positively charged- results in an electric field with the mitochondrial matrix being negatively charged
how is the proton motive force calculated
chemical gradient + charge gradient
what is the symbol for proton motive force
delta p
what is the symbol for chemical gradient
delta pH
what is the symbol for charge gradient
delta psi
describe ATP synthase
two functional domains
f0 and f1
describe the f0 domain
is embedded into the inner mitochondrial membrane and has a proton pore through which protons leak
a single unit binds to the outside
what are the subunits of ATP synthase
F1
F0
axle
stator
describe the F1 matrix
it extends into the mitochondrial matrix and contains the catalytic activity of the synthase of ATP
ADP+Pi—> ATP+H20
what is the free energy in the reaction of ATP synthase
free energy change close to zero
and is readily reversible
how many units does F1 contain
5 units 3x alpha 3x beta delta epsilon and upsilon
what subunit connects the F1 unit to the F0 unit
epsilon and an external column called a stator
what does the F1 region do
binds the ADP +Pi
catalyse the reaction of ATP
release the ATP
what does the F1 region look like
3 alpha and 3 beta hexamer ring
which structure rotates in the F1
the gamma structure rotates only and not the alpha and beta
what is contained in the 3 alpha in the hexamer ring
contain bound ATP but does not participate in the reaction
what three states is beta found in the F1 structure
open
loose
tense
where is ATP released out of from the beta subunits of F1
only in the OPEN STATE
what happens in the tense state of the B subunit of F1
the ADP+Pi are close enough to produce ATP
what is the evidence of rotational catalysis
genetically engineered f1 allowed for the attachment of ATP synthase to a Ni complex
biotin was covalently attached to C on F0
and the actin was labelled with a fluorescent probe and found to move when ATP was introduced as a substate
how are the electrons from NADH transported into the mitochondria
via the G3P shuttle
describe the G3P phosphate shuttle
- a pair of electrons are transferred from NADH to dihydroxyacetone phosphate
- forming glycerol 3 phosphate via the enzymatic catalysis using cytoplasmic G3P dehydrogenase
- G3P is deoxidised to DHAP via G3P dehydrogenase
- electron pair is transferred to FAD forming FADH2
- the reduced flavin transfers the electrons onto Q cycle
what electron shuttle occurs in the liver and heart
the malate aspartate shuttle
describe the malate aspartate shuttle
- electrons are transferred from NADH to oxaloacetate producing malate
- malate then moves through the membrane and deoxidised by NAD+ via malate dehydrogenase
- glutamine reacts with oxaloacetate forming aspartate
- aspartate then moves out via the exit shuttle
how does ATP and ADP move into the inner mitochondrial membrane
ATP-ADP translocase
how many transporters are coded into the human genome
40
give some examples of the transporters coded by the human genome
ATP-ADP translocase dicarboxylate carrier tricarboxylate carrier pyruvate carrier phosphate carrier
what are other ways ATP can be produced
by uncoupled mitochondria- a type of brown fat adipose tissue generates heat
contained in this is an unique uncoupling protein which bypasses the f0 and f1 complex so the energy of oxidation is dissipated as heat
what does 2,4 Dintrophenol do
it uncouples the electron transport by directly transporting proteins across the mitochondrial membrane- ATP not synthesised
what can 2,4 Dinitrophenol do
photographic chemical
a fertiliser
used in dyes and explosives
was used for weight loss in 1933 but banned in 1938
what molecules inhibit the electron transport chain
rotenone
antimycin A
cyanide and carbon monoxide
