Oxidative phosphorylation

Location of TCA

matrix of mitochondria

Location of oxidative phosphorylation

inner mitochondrial membrane

cristae

folds in the inner membrane of mitochondria

inner mitochondrial membrane permeability

relatively impermeable

outer mitochondrial membrane permeability

relatively permeable

area of the mitochondria with the highest pH

matrix

ATP reactants

Pi and ADP

Where does the energy to make ATP come from?

flow of protons across membrane down the electrochemical gradient

Direction electron carriers move protons

pumps H+ against the concentration gradient out of the mitochondrial matrix as electrons flow to O2

Direction ATP synthase moves protons

downhill flow of H+ with the concentration gradient into the mitochondrial matrix as ATP is formed

How many electrons can FAD carry?

2 e- in complex II (one at a time)

cytochromes a, b, and c

located in larger protein complexes. Each can carry 1 e- in the IMS, stored on the iron in a heme group

cytochromes bound ionically to complex

a and b

cytochromes bound covalently to complex

c

iron-sulfur clusters

carry 1 e- at a time, in complex I, II, and III

Coenzyme Q

aka ubiquinone, can be reduced to ubiquinol or QH2

QH2

fully reduced, carries electrons through nonpolar space in the membrane between complexes

Complex I enzyme name

ubiquinone oxidoreductase

AKA NADH dehydrogenase

Complex I mechanism

uses NADH + H+ and Fe-S clusters to transfer electrons to QH2

Result of Complex I

2H+ reduce Q to QH2

4H+ are pumped across the membrane

Complex II enzyme name

succinate dehydrogenase

Complex II mechanism

succinate to fumarate produces FADH2 and the Fe-S clusters transfers e- from FADH2 to form QH2

Result of Complex 2

formation of QH2

no proton transport

Complex III enzyme name

cytochrome bc1

complex III mechanism

Q cycle

Result of Complex III/Q cycle

electron transport from 1 QH2 to form 2 cytochrome c

4H+ transferred to IMS per QH2

The Q cycle

QH2 transfers 1 e- to cytochrome c and transfers its other e- to Q forming Q- (2 H+ to IMS)

Another QH2 transfers 1 e- to another cytochrome C and transfers its other e- to the Q- forming QH2 (pump 2H+ to IMS)

Complex IV enzyme name

cytochrome oxidase

Complex IV mechanism

uses copper a to accept e- from cytochrome c and copper b to transfer 4 e- to oxygen allowing it to bind 4H+ and reducing it to 2 H2O

Result of complex IV

2 H2O and 4H+ pumped into IMS

Main job of complex I and II

form QH2

Major job of complex III

QH2 transfer e- to cytochrome c

Major job of complex IV

e- reduce O2 to H2O

How many protons are pumped across to IMS by complexes I, III, and IV?

10 H+

Proton-motive force

The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (H+) across a biological membrane during chemiosmosis.

3 ways the electrochemical proton gradient is created

1) active H+ transport to IMS

2) Chemically remove protons from the matrix

3) release protons into the IMS

What complexes are responsible for active H+ transport to IMS?

I and IV

What complex chemically remove protons from the matrix?

IV

What release protons in the IMS

oxidation of QH2 (III/Q cycle)

Where is the H+ concentration higher?

IMS, intermembrane space

Makeup of F1 ATP synthase

3 dimers, with 3 possible conformations

open conformation F1 ATP synthase

nothing bound

loose conformation F1 ATP synthase

ADP and Pi bound

tight conformation F1 ATP synthase

ATP bound

What drives the rotation of the gamma subunit?

Proton motive force

Regulation of oxidative phosphorylation

substrate availability, product inhibition, mass-action ration ([ATP]/[ADP])

How is oxidative phosphorylation affected by hypoxic conditions?

ETC/ATP synthesis slows

ATP synthase is inhibited to prevent reverse reaction (ATP -> ADP + Pi)

Accumulation of NADH