oxidative phosphorylation

Where does oxidative phosphorylation take place in eukaryotes

Mitochondria

What does oxidative phosphorylation depend on

Electron transfer

The electron transfer potential of an electron is measured as

Redox potential

Redox potential

Measure of a molecules tendency to donate or accept protons

Standard free energy change in relation to change in reduction potential

ΔG°’ = -nFΔE’₀

Oxidant

Oxidizing agent, the acceptor of electrons in a redox rxn

Reductant

Reciting agent, the donor of electrons in a redox rxn

What kind of reduction potential would NADH have if it donates electrons

Negative reduction potential

What kind of reduction potential would O2 have if it accepts electrons

Positive reduction potential

Coenzyme Q/ubiquinone

Lipid soluble conjugated dicarbonyl compound. Can carry 2 electrons

Cytochromes

Iron coordinating porphyrin ring derivatives. A,b, or c differ by ring additions and they can carry 1 electron

Iron sulfur proteins

Coordinated by cysteines in the protein. Contain equal number of iron and sulfur atoms. Carry 1 electron

Electron transporters

Cytochrome, ubiquinone, iron sulfur proteins

Complex 1- NADH-Q Oxidoreductase complex

Oxidizes NADH, which is generated through the Krebs cycle in the mitochondrial matrix, and it uses the 2 electrons (Q2- picks up from matrix) to reduce ubiquinone to ubiquinol. Protons are pumped into inter membrane space forming proton gradient.

Complex 2- succinate-Q reductase

Succinate dehydrogenase is the citric acid cycle is a part of complex 2. The FADH2 generated in the citric acid cycle reduced Q to QH2 which enter the Q pool. Move free electrons through a series of iron sulfur clusters and into ubiquinone forming ubiquinol. Not a proton pump

Complex 3- Q-cytochrome c Oxidoreductase

The removal of 2 persons form the matrix contributes to the formation of a proton gradient. Cytochrome b recycles both electrons of QH2. Accepts electrons from unbiquinol and transfers to cytochrome c

Complex 4- cytochrome c oxidase

Accepts electron one at a time from cytochrome c. Donates electron to oxygen to form water. Accepts 4 electrons from cyt c and 4 protons in the matrix. 2 heme groups: a and a3. 2 copper ions: CuA and CuB

Chemiosmotic hypothesis

Movement of ions through semipermeable membrane down their electrochemical gradient

What is responsible for ATP synthesis

Proton motive force

Proton motive force

Chemical gradient + charge gradient

ATP synthase

Dimer structure with a Fo and F1 portions. Spans from intermembrane space (high [ ] of protons) to mitochondrial matrix (low [ ] of protons)

Fo

ATP synthase portion that contains the c ring and is embedded in a he lipid bilayer

F1

ATP synthase portion in the mitochondrial matrix. Has the alpha- beta ring

Proton flow around the c ring

Subunit a, which abuts the c ring, has 2 channels that reach halfway into the a subunit. One half channel opens to the inter membrane space and the other to the matrix. Protons enter the half channel facing the proton rich intermembrane space, bind to a glutamate residue on one of the subunits of the c ring and then leave the c subunit once they rotate around to face the matrix half channel making a full turn

How does the c ring power ATP synthesis

The force of the proton gradient powers the rotation of the c ring. The rotation of the c ring powers the movement of the gamma subunit which in turn alters the conformation of the beta subunits

Catalytic beta subunits of the F1 component

O, L, T forms that cycle through these three conformations.

O form

Nucleotides bind to or be released from the beta subunit

L form

Nucleotides are trapped in the beta subunit

T form

ATP is synthesized from ADP and P

Can two subunits be in the same conformation in the F1 component

No, subunits are never in the same conformation

Which way does the ATP synthase mechanism turn

Counterclockwise, 120 degrees. When protons enter the mechanism, it’s divided by three to see how many are needed for 1 turn

Glycerol phosphate shuttle

In muscle. Facilitates the transfer of electrons from cytosolic NADH to mitochondrial FADH2

Malate aspartate shuttle

Used by mitochondria for transporting electrons produced during glycolysis across the impermeable inner membrane for oxidative phosphorylation