cell integrity Flashcards
what is substrate level phosphorylation?
when ATP or its equivalents are produced directly by kinase
where is the bulk of ATP produced?
oxidative phosphorylation in the inner mitochondrial membrane
what are cristae (mitochondria)
folds of the inner membrane increasing surface area
where does oxidative phosphorylation take place?
inner membrane of mitochondria
outline the reaction of NADH re-oxidation
NADH + H+ + 1/2O2 ——> NAD+ + H2O ΔG -223Kj/mol
outline the reaction of FADH2 re-oxidation
FADH2 + H+ + 1/2O2 ——> FAD + H2O ΔG -170Kj/mol
what does the electron transport chain consist of?
4 membrane proteins : complex I-IV
2 mobile electron carriers: co-enzyme Q and cytochrome C
other names for complex I
NADH-Q oxidoreductase or NADH dehydrogenase
other names for complex II
succinate-Q reductase or succinate dehydrogenase
other names for complex III
Q-cytochrome C oxidoreductase
other names for complex IV
cytochrome c oxidase
other name for co-enzyme Q
ubiquinone
which complexes do protons pass through?
I,III and IV
where else is complex II used?
Krebs cycle (succinate dehydrogenase)
where does FADH2 enter the electron transport chain?
complex II so skips a proton (one less proton and so less ATP produced than NADH)
define redox reactions
electron transfer reactions involving a reduced substrate(which donates electrons and becomes oxidised) and an oxidised substrate(which accepts electrons and becomes reduced)
what is a redox couple?
a substrate that can exist in both oxidised and reduced forms
what is a redox potential?
the ability of a redox couple to accept or donate electrons
what reference do standard redox potentials use?
hydrogen electrode
what does a negative E0 imply?
the redox couple has a tendency to donate electrons(more reducing power than hydrogen)
what does a positive E0 imply?
the redox couple has a tendency to accept electrons(more oxidising power than hydrogen)
what happens to the electrons as they are passed down the electron transport chain?
they lose energy
what type of enzyme is ATP synthase?
multimeric
what are the parts of ATP synthase?
membrane bound F0 and an F1 part which projects into the matrix space
how does the enzyme alter affinities for ATP and ADP?
by rotating due to proton flow
if protons flow into matrix space what is the reaction on ATP synthase?
Pi + ADP ————> ATP
if protons flow out of matrix space what is the reaction on ATP synthase?
ATP ———–> Pi + ADP
what is the most common cause of oxidative phosphorylation failure?
lack of oxygen
hypoxia- diminished
anoxia- total
what is oxygen uptake of mitochondria controlled by?
ADP and Pi
what are metabolic poisons?
molecules that interfere with electron flow in the ETC or with proton flow
how is cyanide and azide a metabolic poison?
binds with high affinity to ferric(Fe3+) form of the haem group in cytochrome oxidase complex blocking the final step of the ETC
how is malonate a metabolic poison?
closely resembles succinate (competitive inhibitor) so binds to succinate dehydrogenase slowing down electron flow from succinate to ubiquinone by inhibiting oxidation of succinate to fumarate
how is rotenone a metabolic poison?
inhibits transfer of electrons from complex I to ubiquinone
how is oligomycin a metabolic poison?
antibiotic which binds to the ‘stalk’ of ATP synthase and blocking flow of protons through the enzyme
how is dinitrophenol(DNP) a metabolic poison?
is a proton ionophore which can shuttle protons across the inner mitochondrial membranes
