oxidative phosphorylation

what are the five oligomeric complexes called

• I NADH-ubiquinone (Q) oxidoreductase

• II succinate-ubiquinone (Q) oxidoreductase

• III ubiquinol- cytochrome c reductase

• IV cytochrome c oxidase

• V atp synthase

where does complex v accumulate

tips of the cristae

ubiquinone (coenzyme q) reduction

• reduced one electron at a time

• intermediate is semiquinone

• then ubiquinol

where does ubiquinone accept electrons from

oxidation of NADH at complex I and FADH2 at complex II

what happens at NADH-ubiquinone reductase

• NADH is oxidised to NAD+

• with flavin mononucleotide FMN to FMN2

• 4 protons are pumped into the inter membrane space

what binds to which module in NADH-ubiquinone reductase

• nadh binds to dehydrogenase n module

• ubiquinone found in q module

• H+ move across the membrane arm P module

which enzyme is common to both citric acid cycle and electron transfer chain

succinate Q reductase/ succinate dehydrogenase

what happens at succinate q reductase

• succinate → fumarate

• allows FAD to be reduced to FADH2

• then reduces ubiquinone to ubiquinol

ubiquniol-cytochrome c oxidoreductase

• captures electrons from ubiqunol to cytochrome c

• 4H+ are translocated

• electrons are transferred from ubiquinol to two molecules of cytochrome c

cytochrome is an electron carrier between which complexes

iii and iv

structure of cytochrome c

• alpha helical haem protein

• iron atom in centre which changes oxidative states

• small

• highly soluble

• associated to inner mitochondrial membrane

complex iv

• receives electrons from cytochrome C carrier, one at a time

• iron atoms and copper atoms are both reduced and oxidised as electrons flow to oxygen

• catalyses the reduction of oxygen and water

• two more hydrogen ions are translocated using free energy

complex v atp synthase

• use the proton gradient energy for the synthesis of ATP

• protons flow back into the matrix via ATP synthase

• 3H+ needed for each ATP

knob and stalk structure of atp synthase

• F1 - catalytic subunits (faces the matrix) KNOB

• F0 - proton channel (embedded in the inner membrane) STALK

what is the main component that allows rotation of atp synthase

• gamma of central axle

arrangement of subunits of F1

• alpha and beta alternate like orange segments - rigid

• gamma in central axle - moves

• delta in peripheral stalk

which subunit of F1 has active site for ATP synthesis

beta

beta subunit conformations

• open state - binds ADP and Pi

• loose state - active site closes loosely on ADP and Pi

• tight state - converts ADP and Pi to ATP

what drives the rotational catalysis

• flow of protons

• drives F0/ gamma rotation

• forced cyclic conformational changes into each beta subunit

how many protons per ATP

3H+/ATP in oxidative phosphorylation

1ATP for transport of Pi across inner mitochondrial membrane