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83 Cards in this Set

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oxidative phosphorylation
electron transport and generatioin of transmembrane proton gradient

ATP synthesis from the proton grad
2 parts of oxidative phosphorylation
1. oxidative-involves oxidation of electron donors like NADH and FADH2

2. phosphorylation- captures energy in the form of ATP synthesis from a proton gradient
Where does oxidative phosphorylation occur?
in Mitochondria
Where do electrons for Oxidative phosphorylation come from?
Beta oxidation of fatty acids
Describe cellular respiration
The cell produces CO2 from the Krebs cycle and consume O2 from the ETC. Cellular respiration also deals with the consumption of electrons
When NADH and FADH2 from krebs goes on to ETC what happens to the electrons?
the e- go from NADH/FADH2 to oxygen and water is released. Since this rxn is so downhill energy is captured as ATP.

2H+ + 1/2 O2 ---> H2O
water is made from the O2
membranes of mitochondria
inner and outer
describe inner mitochondrial membrane
large suface area bc many infoldings

impermeable (tightly sealed) unless a transporter is presents (ex is pyruvate transporter)

2 sets of enzyme complex
1. move e- down ETC, they are membrane bound carriers.
2. to make ATP
2 sets of enzymes in inner mitochondrial membrane
1. move e- down electron transport gradient (membrane bound carriers involved with prton transfer)

2. ATP synthesis
Describe outer membrane
True membrane but leaks so it allow metabolites that are small and ions through holes called porins. Therefore, things like pyruvate can get in mitochondrial matrix
are matrix and cytoplasm mixed?
no mit. matrix is isolated from cytoplasm
what is between inner and out mit membrane?
intermembrane space is between the inner and outer mit. membrane. It is similiar to cytoplasm but it holds unique proteins and has a special role in oxidative phosphorylation
overview of Oxidative phosphorylation
electrons flow through the chain of membrane bound carriers in the inner mit. membrane

Free energy released is used to transport protons uphill across the inner membrane (oxidative)

Transmembrane flow of protons down their conc. graient provides free energy for ATP synthesis via ATP synthase (Phosphorylation)
properties of NADH
good at carrying e- in aqueous solution but not in membrane

v. mobile to carry around e-

Carries 2 electrons

always in NAD form to capture e- from catabolic pathways then the NADH form goes to ETC
function of nicotinamide nucleotide linked dehydrogenasees
collec e- from catabolic rxns and transfer them to water (NADH)
seperate that NADH

always in NADPH form to give e- for anabolic rxns
orgin of e- from catabolism
FMN and FAD properties
stuck to protein so very immobile

can carry one electron as (semiquninone) or two electrons (FADH2 or FMNH2) so very versatile
What does FAD and FMN reduction potential depend on?
protien microenvironment
Since NADH can only carry e- in aqueous solution, what is need to transfer e- to Q?
need protein prosthetic groups
Describe Ubiquinone (coenzyme Z)
it is a downstream electron reducing equivalent

it has long hydrophobic tail with 50 Carbon units it the lipid bilayer.

Quninone is the active group and it has 2 ketone carbonyls that can be reduced to hydroxyls

Q carries E- is the membrane
How many e- can Q carry?
one or two bc has two carbonyl ketone groups

carry one e- (semiquinone)

Carry two e-(fully reduced Q)
have Fe containg heme prosthetic group in center to carry the e-

Type of protien prosthetic group to get e- from NADH to Q.
3 classes of cytochromes

cytochrome protein with heme group is colored bc of the resonance in the double bond. so a,b,c differentiated by light absorbtion
difference is cytochrome a, b, and c
a has long carbon chain that is anchored to a lipid bilayer. it is an integral membrane protein

b is a porphin ring also a integral membrane protien

c has a group with a convalently linked cysteine. c is water soluable but ionically associated with outer suface of inner mitochondrial membrane
purpose of difference in cytochrome a, b, c
the cytochromes are protein prosthetic group. Each type of cytochrome is found at a different level in the ETC bc each one hold e- at a different affinity and have different reducing potentials
what does absorbtion spectrum of cytochrome c tell us
reduced cytochrome c (fe 2+) has major absorbtion at 400 nm and and minor absorbance at 540 nm. The oxidized (fe 3+) absorbance goes down at 400 nm and 540 nm bc color changes. So you can tell how oxidized or reduced the cytochrome is and determine at what place it is in ETC
Iron sulfer proteins
used to hold e-

Dont use heme group but do have iron groups that bind to sulfer atoms of side chains of cystiene residues.

2 arms fold to make horse shoe so adjacent sulfidyl groups coordinate iron and inorganinc sulfate is in v. center.

the Fe groups hold the e-
What are Rieski protiens?
iron sulfur protiens
5 major classes of e- transporters
Iron sulfer proteins
describe standard reduction potential of ETC
net is E=very + therefore G is very negative so alot of nrg is there so it takes several steps bc there is so much energy it is too much energy for just one enzyme/protein to handle. So bits of nrg are captured at each step. ETC has many stair steps to give little energy at each step
How is energy saved in ETC?
energy is basically saved as acid most stair step of the way. Acid is pumped from matrix across intermitochondiral membrane and stored in the cytoplasm to make a huge proton gradient. The cytoplasm is approx 1 pH unit lower than the matrix
4 ways to interfere with oxidative phosphorylation
1. ihibition of electron transfer

2. inhibition of ATP synthase

3. uncoupling of phosphorylation from eleltron transfe

4. inhibiton of ATP-ADP exchange
how does cyanide intere with ox phos?
by inhibition of ETC bc it binds to chytocrome oxidase instead of oxygen
How does carbon monoxide interfere with oxphos?
How does Rotenone interfere with ox phos?
it inhibits ETC by preventing electron transfer from Fe-S center to ubiquinone (inhibits e- transfer from NADH to Q)
how does oligomycin interefere with oxphos?
it inhibits ATP syntase by blocking proton flow
3 compounds that inferefere with oxphos by uncoupling phsophoylation from electron transfer
How does Antimycin A interfere with oxphos?
inhibits ETC bc it blocks e- transfer from cytochrome b to cytochrome C1
(reduced end)
Cyt b
(oxidized end)
What happens with antimycin A?
block e- from going from cyt b to cyt c1 so cytb gets way reduced and cyt c gets really oxidized and you can see this with a spectrophotometer looking at absorbance
what does cyanide and carbon monoxide block?
transfer of e- from cyt a to oxygen.
how can the 4 multienzyme complexes wi the inner mit membrane be isolated/
fist use digitonin, a mild detergent, to strip away the outer mit membrane

then put the mit. in water and it will lyse breaking apart the inner mit mem. into fragments (osmotic rupture)

Take a fragment and use a stron nonionic detergent to seperate the four multienzyme complexes then seperate with chromatography to see how they work individually
4 enzyme protin complexes of the mitochondrial electron transfer chain
I NADH dehydrogenase

II Succinate dehydrogenase

III ubiquinone cytochrome c
oxidoreductase and cyt c

IV cytochrom Oxidase

all are found in the inner mit. membrane
6 electron carriers

*remember that metals aid in carrying electrons!
4 ways to get electrons to Q which is in the center of the inner mit. membrane
I. NADH from the matrix gives its e- to FMN and FeS which then give the e- to Q in the inner mit membrane space. Q can then diffuse into intermembrane space in mit. and go anywhere

II. membrane bound succinate dehydrogenase from matrix side makes FADH2. e- then go to FeS then to Q in inner mit membrane

III membrane bound acyl Co A dehydrogenase from beta oxidatatioin on inner mit membrane (matrix side) passes e- and goes through 3 subunits then to Q

IV. weird only one from cytoplasmic side. glycerol 3 phosphat dehydrogenase gives electrons to FAD then goes to Q
Describe how complex I transports e- and protons across membrane
NADH from matrix gives 2 e- to FMN then goes to FeS then to Q.

Also protons from the matrix leave and diffuse across inner mit membrane and into intermembrane space (cytoplasm)

For every 2e- that go through complex I, 4 protons are transported to intermembrane space to conserve energy

NADH + 5H+n + Q
-> NAD+ + QH2 + 4 H+p

so the H from NADH is added to Q and a H from the matrix (n) is added to Q to make QH2 and the other 4 H+ enter intermembrane space
Describe complex II
Succinate binds to substate binding site on complex II and want to go to QH2 (made from complex I) but cant bc it is so far away so it uses 5 steps each with a different Fe carrier at each step. Each step is less than 10 A apart from the other so the e- moves easily.

A heme b is also in complex II to grap any electrons that accidently leave the path.
Describe complex III
Transfers one e- from QH2 to Cyt C and the other e- to semiquinone (Q-) to make another QH2

complex III is where all tributaries converge to give up 2 e-

QH2 + cyt c(oxidized) + 2 H+n
-> Q + 2 cytc (reduced) + 4Hp

the 2 H+n comes from QH2

so 4H+ enter the cytplasm
How many electrons can each eytochrome carry?
Describe complex IV
4 cyt C with 4 e- (1 e- per cyt c) comes in via Cu centers. An oxygens is captured by a heme group and e- is put on oxygen. protons collected from matrix add to oxygen to make water. 4 H+ are pumped into the cytoplasm per 2NADH or 1 Oxygen

4 Cytc (red)+ 8H+n + O2
->4 cytc(ox) + 4H+(p) + 2H20

4 of the H+ from matrix go to cytoplasm and the other four are used to make 2 waters
How many e- does each NADH give?
enough to make only 1/2 of an oxygen and to pump 2 H+ to cytplasm. So you need tow NADH to make 1 Oxgen and 4 H+ to be pumped
summary of e- and proton transport
NADH give e- to I and 4 H+ transferred to cytoplasm. succinate gives e- to to all the e- goes to Q which is a lipid carrier lipid soluable complex that picks up the e- and gives them ti complex III and here 4 H+ are transferred to cytoplam. Complex III gives e- to Cyt C and in complex IV Cyt C gives e- to water and 2 H+ go to cytplasm
final product of ETC
Purpose of proton motive force
generate ATP
2 parts of proton motive force
1. chemical potential energy H+ gradient

2. electrical potential enrgy (charge seperation)

basically the G is a ratio of concentraion of solute across membrane and electric field in Volts
what is the gradient an example of ?
potential energy
how is energy from oxidation recovered?
90% of energy recovered in proton gradient so it is very efficient
How is proton gradient used?
to do work to put ADP + P to make ATP. It involves a mechanical method. Protons come into F0 which is transmembrane and causes F1 to turn making mechanical motion
Describe chemiosmotic model
2 parts
1. electron transport chain
2. ATP synthase brings back the protons

cannot make ATP without pumping protons this is known as coupling
when using drugs to look at coupling of proton pumping and ATP synthesis, what happens when succinate, pyruvate, or CoA is addded?
they are e- donors so increase oxygen consumption, proton pumping and ATP synthisis bc they are all coupled
when using drugs to look at coupling of proton pumping and ATP synthesis, what happens when CN- is addded?
inhibits the ETC so there is no proton gradient and therefore no ATP is made
when using drugs to look at coupling of proton pumping and ATP synthesis, what happens when oligomyacin is addded?
oligomycin inhibits ATP synthase so stops the ETC too but takes a second.
when using drugs to look at coupling of proton pumping and ATP synthesis, what happens when the ionophore DNP is addded?
DNP is soluble in the membrane. It carriers protons and breaks down the proton gradient. When DNP is added it blocks ATP synthesis but keeps consuming oxygen and carrying e- so it basically uncouples the two processes
Rxn coordinat for ATP synthase. How is it unique?
the ATP synthase allows ATP synthsis to have lower enegy that ADP + P. when the enzyme is bound to ATP it has lower energy that regular ADP + P but energy is needed to uncouple the ATP synthase and ATP bc they are v. tightly bound. The ATP wo the enzyme is hi energy
2 parts of ATP synthase
1. embeded in membrane (F0)
2. stalk that sticks out of membrane (F1)
describe F1 of ATP synthase
3 identical alpha/beta subunits. 1 binds ATP, 1 binds ADP, and 1 is empty

basically 3 dimers all in a different state

also has gamma chain which is off center and rotates and bumps the dimers
describe F0 and how F1 and F0 fit together.
F0 is inside the membrane. It is composed of alpha helices lined up longitudinally. the F1 gamma subunit sits on the F0
Why is it called F0
for F oligomycin
How does F0 and F1 work together as ATP synthase?
downhill movement of H+ throgh the F0 pore drives the rotation of F0 and the attached gamma from F1. the rest of F1 (alpha and beta subunits) are stationary bc anchored to b2 stator. The off center gamma subunit touches the alpha/beta subunits from the inside and induces the release of the bound ATP
how many ATP are made for each turn of ATP synthase?
3 ATP are made per turn
3 purposes of proton motive force
1. make ATP
2. get ATP into mit matrix
3. get phosphate into matrix
how does ATP get from the matrix to the intermembrane space?
by carrier called adenine nucleotide translocase. It is an antiporter bc it exchanges one ADP into matrix for one ATP out of matrix and into intermembrane space. It is driven by transmembrane electrochemical gradient
How does phosphat get into the matrix?
uses phosphate symporter as protons come down coc gradient phosphate comes with them going up their conc gradient.

driven by proton gradeint.
How does NADH get across iner mit membrane and into the matrix?
in intermembrane space NADH gives H to oxaloacetate to make malate, the malate has transporter to get to matrix. In matrix the malate is converted to oxaloacetate by giving proton to NAD to make NADH. This NADH can go to ETC. problem is the oxaloacetate could run out so need to convert it to the aa aspartate by aminiation. the aspartate then goes back through transporter to intermembrane space. the aspartate give it amino group to aKg to make glutamate and asp becomes oxaloacetate. the glutamate goes back to matrix.
describe the glycerol 3 phospate shuttle
used in skeleton and brain
makes only 1.5 ATP not 2.5 bc uses FADH2 instead of NADH

glycerol derivitive dihydroxyacetone phosphate takes e- from NADH and to make glycerol 3 phosphate, the glycerol 3 phosphate gives e- to FAD to make FADH2 which gives e- to Q.
how many ATP are made from one NADH? one FADH2?
2.5 ATP made per NADH

1.5 ATP made per FADH2
Amount of ATP made from complete oxidation of glucose

most ATP made from ox phos
only 4 come from substrate level phosphorylation
main ways to regulate oxidative phosphorylation
acceptor control ration. need ADP in matrix

Mass action raton which is ATP/ADP is v. hi so always have ATP
Protien 84aa inhibitor IF1
since ATP synthase can go forward or backward it inhibits ATP synthase in ischemia w/ lo pH from pyruvalte or lactate build up
like DNP. It uncouples ATP synthesis from oxidation so allows ETC to run without ATP syntheiss. THe energy of oxidation is lost as heat. This is really good for brown adipose tissue bc has lots of mitochondira with cytochromes so baby can get warm
with product inhibiton what happens when there is alot of acetyl CoA?
inhibit pyruvate dehydrogenase
with allosteric regulation, what happens to PFK1 with hi Citrate?
Citrate will diffuse back into the cytoplasm and inhibit PFK1 with is the regulatory step of glycolysis.