The electron transport chain

What is the redox potential

describes the point at which half of the molecules are reduced and half are oxidized

What does the ETC do

couples the oxidation of NADH or FADH2 adn the reduction of O2 with the transport of protons

What is the final electron receptor

O2

What are the components of ETC

4 large protein complexes in/on the inner mitochondrial membrane

What are the protein complexes

FMN, Fe-S cluster, heme

what is the lipid soluble electron carrier

coenzyme Q

what is the water-soluble electron carrier

cytochrome C

What do electrons do

pass freely from a molecule that has a lower redox potential to a molecule that has a higher redox potential

What is the thermodynamic efficiency is thought to be

70%

What are the cofactors and prosthetic groups of the ETC

Nicotinamide adenine dinucleotide

Flavin mononucleotide and flavin adenine dinucleotide

coenzyme Q

Iron-sulfur cluster

Heme

What is NADH

free water-soluble electron carrier

what does NADH transfer

2 electrons

What is often the first step of the ETC

oxidation of NADH to NAD+

What is FMN and FADH2

water soluble but protein bound electron carriers that are tightly bound resulting in flavoproteins)

What does FADH2 and FMN transfer

1 or 2 electrons

What can FMN and FADH2 generate

a semiquinone

What is coenzyme Q

free lipid soluble electron carrier

What does coenzyme Q transfer

1 or 2 electrons

What can coenzyme Q generate

a semiquinone

What is the iron-sulfur cluster

protein bound electron carrier

What is transferred by Fe-S

1 electron

How is Iron-sulfur cluster found

as 2Fe-2S or 4Fe-$s configurations

What does the electron do

transferred to sulfur which is then stabilized by iron

What are heme’s

protein bound electron carriers (cytochromes)

How many electrons do Heme transfer

1

What does heme consist of

a large porphyrin ring and Fe atom in the center

What are the protein complexes of ETC

Complex I,II,III,IV

What is complex I

NADH-coenzyme Q oxidoreductase

What does complex I do

accepts electrons from NADH

What first accepts electrons from NADH

FMN

What are the components of complex I

FMN, Fe-S, and electron given to CoQ

What is electron transfer coupled with in complex I

proton translocation from matrix to IMS

What is complex II

succinate-coenzyme Q oxidoreductase

What does complex II do

accepts electrons from succinate

what are the components of complex II

FAD, Iron-sulfur clusters, Heme b, electrons given to CoQ

What is electron transfer not coupled with in complex II

proton translocation

What do complex I and II do

do not work in series but accomplish the same result of reducing CoQ

What complex is also a part of the TCA cycle

complex II

What is complex III

coenzyme Q-cytochrome C oxidoreductase

what does complex III do

passes electrons from reduced CoQ to cytochrome c

components of complex III

two b-type cytochromes

cytochrome c1

one iron-sulfur cluster

electrons given to cytochrome c

electron transport in complex III is

bifurcated

one electron from CoQ in complex III is given to

iron-sulfur cluster

How is this electron transported to cytochrome c

via cytochrome c1 (high potential chain)

What happens to the 2nd electron

transferred to an oxidized CoQ via the b cytochromes (low potential chains)

What is that process in complex III known as

Q-loop mechanism for proton translocation

What is complex IV

cytochrome c oxidase

what does complex IV do

oxidizes cytochrome c an reduces O2 and H2O

components of complex IV

two heme a

3 copper atoms

what is the final electron receptor of complex IV

O2

what does complex IV pump

protons across the membrane

What are electrons from cytochrome c transferred to

the first group of copper atoms

Electrons are then transferred to

heme a

finally to

the lone copper atom where it is used to reduce O2 to H2O

What complexes use the passage of electrons to translocate protons from the matrix to IMS

complex I,III, IV

what is the proton motive force created by

large proton gradient

What is the PMF used by

complex IV to synthesize ATP

What is complex V a part of

oxidative phosphorylation

what is complex V

ATP synthase; multisubunit transmembrane protein

what is F₀

a water-insoluble transmembrane protein

what is F₁

a water-soluble peripheral membrane protein that sticks into the matrix

What complex is a rotary engine

V

What does F1 have

3 catalytic sites

what does rotation of gama subunit do

acts as a molecular camshaft that causes the catalytic sites to change shape

what is the rotation a result of

the proton gradient-driven F0 engine

what is each catalytic site in

different conformations

site 1

ADP bound and ready for release (T)

site 2

ADP + Pi bound and ready for synthesis (L)

site 3

Empty (O)

Each site

gets cycled through the different configuration

what inhibits electron transport in complex I

Rotenone: a plant toxin used by amazonian Indians to poison fish, also used as insecticides

What is a pesticide that blocks electron transport in complex III

antimycin A

what does cn and carbon monoxide block

electron transport in complex IV

what blocks complex V

oligomycin

what have been found to uncouple electron transport and ATP sythesis

compounds such as 2,4-dinitrophenol (DNP)

What does oxidative phosphorylation uncoupled from ETC do

increases permeability of inner mitochondrial membrane to H

What does the ETC sense

the loss of PMF and works to rebuild and produces heat

What was DNP used as

a diet pill

what does uncoupling in brown adipose do

generates heat; nonshivering thermogenesis

what are the other sources of heat

ATP hydrolysis that occurs during muscle contraction

What does the mechanism of heat generation in brown fat involve

regulated uncoupling of oxidative phosphorylation, mitochondria contain a proton channel uncoupling protein (thermogenin)

What does partial oxygen reduction produce

ROS

what are all classes of biological molecules susceptible to

oxidative damage caused by free radicals that include lipids, DNA, and enzymes

What has this observation led to

free-radical theory of aging