mitochondria and oxidative phosphorylation Flashcards
pattern of mitochondrial genetic disorders inheritance
maternal
why is succinate added in an assay for ATP synthesis
substrate for ATP synthesis
succinate – fumarate
FAD+ – FADH2
why are some people’s symptoms less severe
heteroplasmy
have a different number of affected chromosomes
gene dosage affect
PCR used to analyse the study - densitometric analysis can reveal the percentage of mutant DNA
why is succinate omitted to measure ATP hydrolysis
see rate of hydrolysis without ATP synthesis occurring
what can be deduced about the nature of the condition
leucine replaced by arginine H+ flow into matrix is impaired H+ flow in hydrolysis direction fine result in death in the mid-teenage years Approaches targeting native ATP6 to the mitochondria are being persued
how is the uptake of oxygen by mt controlled
by components of ATP production, Pi and ADP
this is respiratory control
it allows the body to adapt oxygen consumption to energy requirements
Describe ATP consumption
ATP lifecycle 1-5 mins recycled 300 times/day hypoxia anoxia - total death of neuron - minute death of muscle - hour
cyanide and azide
bind high affinity to Fe3+ in cytochrome oxidase complex
block flow of electrons and ATP production
malonate
resemble succinate
competitive inhibitor off succinate dehydrogenase
slow flow of electrons to ubiquinone
rotenone
inhibit electron transfer from complex 1 to ubiquinone
oligomycin
AB
inhibit ox phos
bind to stalk of ATP synthase
dinitrophenol
proton ionophore
shuttle protein across inner mt mem
Explain the symptoms of luft’s syndrome
unable to respire at maximal rate - lack of respiratory control
oligomycin doesn’t block oxygen consumption - protons enter matrix free of ATP synthase
can phosphorylate substrates efficiently
uncoupled - little effect with DNP
dissipation of energy as heat - perspiration and low weight
describe non-shivering themogenesis
regulated uncoupling in brown adipose tissue in newborn and hibernating animals
hormones - release of fatty acids - activate thermogenin
uncouple
DNP use
weight loss
pesticides
mitochondria
double membrane (cristae)
ox phos - inner mem
TCA - matrix
origin of mitochondria
endosymbiosis mt only arise from mt own genome - similar to prok own protein synthesis similar to prok start AA is fMet (prok) not Met (euk) AB block protein synth in mt
mt DNA
circular genome several copies ion each cell transmitted by ovum NADH and FADH2 re-oxidised - energy released enough to make phosphanhydride bonds this is recovered by etc
chemiosmotic model of ox phos
translocation of protons from within matrix
pumped protons back into matrix
the etc
enzymes: NADH dehydrogenase complex, cytochrome b-c1 complex, cytochrome oxidase complex
carrier: ubiquinone (co-enz Q), cytochrome C
proton accept e-, H+ pump
describe Redox
substance that can exist as both oxidised and reduced form - redox couple
rredox potential - ability to be oxidised/reduced
standard redox potentials E’0 measured experimentally
-ve - more reducing power
energetically favourable
ATP synthase
multimeric enzyme
membrane bound part F0 and F1 - project in matrix
rotation drive transition state
conformational energy flow from catalytic subunit into the bound ADP and Pi - ATP
direction of flow alters hydrolysis/synthesis
succinate dehydrogenase communicate with ubiquinone - one less proton into membrane space - less ATP
describe the oxygen electrode
measures ox conc
base of chamber Teflon membrane permeable to ox
2 electrodes pt cathode and ag anode
small voltage - ox through Teflon reduced - water pt
ag oxidised to AgCl by electrolyte
resulting current proportional to ox conc
sample of mt in chamber - effect of substances on etc
