electron transport

electron carriers transfer e- from reduced coenzymes (NAD and FADH), E from ΔG of these reactions is used to generate ATP

protons are pumped across membrane--gradient used to make ATP

oxidative phosphorylation

reducing power from ETC converted to ATP energy

terminal oxidation (2 components)

electron transport and oxidative phosphorylation

location of terminal oxidation

mitochondrial inner membrane

Where do the reduced coenzymes used in term ox come from?

NADH: glycolysis (transported to mito matrix by shuttles), PDH, TCA, fatty acid beta-ox

FADH: TCA & fatty acid beta-ox

oxidation-reduction

electrons transferred from e- donor (reductant) to e- acceptor (oxidant)

oxidation-reduction potential

 E₀ --capacity for a donor to give up its e- to an acceptor

measured in volts

value compared to standard reference half-cell, usually hydrogen electrode rxn

large neg E₀= strong reducing agent (lose e-), pos=oxidizing agent (accepts e-)

redox pair

e- donor and e- acceptor

potential of standard hydrogen electrode at physiological pH

@ pH 7 = -.42 V

vitamin and mineral cofactors in ETC (5)

NAD

FAD

FMN

iron

copper

ETC components

4 multi-subunit enzyme complexes with redox systems

Complex I-IV

Coenzyme Q

cytochrome C

Path of NADH thru ETC

Complex I --> II --> CoQ -->III --> cyto C -->IV

vitamin C and ETC

necessary for fuctioning of cytochrome C

path of FADH2 thru ETC

enters at II or CoQ --> III --> cyto C --> IV

since it enters later, only 2 ATP are created/ FADH molecule compared to 3/ NADH molecule

ETC products

oxygen (final electron acceptor) + H --> WATER

rotenone

fish poison

inhibits ETC complex I

amytal

barbiturate

inhibits ETC complex I

antimycin A

antibiotic

inhibits ETC complex III

cyanide, azide & CO in ETC

inhibit terminal step at complex IV

cyanide: binds to Fe³⁺ in heme a3 of cytochrome c oxidase enzyme in complex IV, preventing O2 from binding to enz

antidote: nitrites convert oxyHb to metHb by oxidizing Fe2+ to Fe3+.  Fe3+ competes with cytochrome a3 for cyanide.  THIOSULFATE causes cyanide to react with rhodanese-->thiocyanate

fate of protons pumped out of matrix

acidic intramemb space/ basic mitochondrial matrix= gradient

protons travel back to matrix through F₁F₀-ATPase (aka Complex V)

F₀ subunit

proton channel subunit: when incorporated into the membrane, memb is permeable to protons

sensitive to oligomycin (poison)

oligomycin

toxin created by bacteria that inhibits F₀ subunit (proton channel) of ATPase

F₁ subunit of ATPase

contains ATPase enzyme which synthesizes ATP on the F1 surface

how ATPase works

NOT actually an enzyme, uses mechanical energy

proton Δs conformation of F₀, turns F₁ and produces ATP

ATP synth reaction

ADP + P_i--> ATP

uncoupling of phosphorylation and respiration

dissipate proton gradient, respiration and ETC no longer coupled to ATP synthesis

Physiological uncoupling protein (UCP-1)

UCP-1

found in brown adipose tissue of newborns and hibernating animals

cold sensation-->triglyceride hydrolysis, which stimulates UCP-1

loc in inner mito memb, has specific pore through which e- transported back into matrix-->E gained not used for ATP synth, but for heat production "non-shivering thermogenesis"

Leber's Hereditary Optic Neuropathy

mitochondrial disease resulting from single base change in mito genes for complex I subunits-->lower activity of complex I

affects CNS, esp optic nerve-->sudden-onset blindness

lower % mut. mtDNA-->sudden-onset blindness in young adulthood, higher %-->dystonia, impaired speech, mental retardation

mitochondrial myopathies

mutations in tRNA

impaired mito protein synth-->dec activity of Complex I and Complex IV

affects CNS

cytochrome b mutations

lowered activity of complex III

exercise intolerance, hypertrophic cardiomyopathy, lactic acidosis in resting state, myoglobinuria

only muscle cells affected, suggests somatic mutation during germ-layer differentiation

Tx: vit C and K-->reduce cyto C/ox NADH, bypassing complex III and CoQ