2- Mitochondria ETC/Respiratory Chain/Oxidative Phosphorylation Flashcards
what happens to most of the energy released from glycolysis and TCA?
its captured by NADH and FADH2
what happens (big picture) to the electrons released from NADH and FADH2?
they flow through the mitochondrial electron transport chain to eventually reduce O2 to H20 as the final electron acceptor (this is why we breathe in O2… >95% of the O2 we use is used by the electron transport chain)
the energy of those two are stored as a proton gradient established across the mitochondrial inner membrane
final equation
NADH + 1/2 O2 + H+ —> NAD+ + H2O
how many atp does glycolysis/oxidative phosphorylation produce?
glycolysis - 2
oxidative phosphorylation ~36
what will stop the ATPase from pumping?
- dont have ATP
- if there is no longer a concentration gradient you are working against
- build up of ADP
- build up of protons inside the vesicle that use the ATPase
ATPase will keep working as long as you have a source of protons
given an impermeable membrane and an ATPase pump that can translocate H+, what happens if you add H+ inside the vesicle?
ATP will be made from ADP
if the proton circuit is uncoupled and there is a leak then what happens?
the gradient will bleed out and it will destroy the energy used for the reaction
what do you need to build a proton circuit to make ATP?
- impermeable membrane
- e- carriers (to hand off e-)
- proton pumps (to make graident)
- ATPase
Explain the impermeable membrane that the mitochondrial inner membrane has
low sterol, cardiolipin, TONS of proteins (60-70% of weight)
has a lipid bilayer
explain the electron carriers in the e- transport chain
more than 20 redox carriers exist
- ubiquinone (Coenzyme Q)
- flavoproteins w/ tightly bound FAD/FMN
- cytochromes (a, b, and c)
- Fe/S proteins (Fe3+ +e- —> Fe2+)
- protein bound Cu (Cu(II) + e- —> Cu(I))
Only mobile carriers are CoQ and cyt c which shuttle around and are not bound by proteins
is e- flow down a thermodynamic gradient favorable?
YES! it is favorable and youre going from one e- carrier to another just handing it off
O2 oxidant or reductant?
O2 is a STRONG oxidant which means it has a high affinity for electrons (0.82)
which complexes do not pump H+ from the matrix to the IMS
Complex II is the only one that does not
I, III, and IV pump H+ to the inner mitochondrial space
all of these are thermodynamically favorable and youre using this to move protons across an unfavorable gradient
proton pumps
complexes I, II, III, IV, and V
V is ATP synthase
ATPase vs. ATP synthase
ATPase- hydrolyses ATP
ATP synthase- makes ATP
Proton pump: Complex I
NADH-CoQ reductase. Transfers two e- to ubiquinone which is a mobile carrier that floats b/w complex 1 and 3 and transfers those e- to complex 3.
in the process of doing that it pumps 4 protons into the inner-membrane space
Proton pump: Complex III
complicated cycle referred to as the q cycle
takes 2 protons from ubiquinole (reduced version of ubiquinone) and takes two protons from the matrix and pumps all 4 of these into the inner-membrane space
cytochrome c
skates along surface of outer membrane and dumps electrons from complex 3 onto complex 4, which is where O2 is consumed and H2O is made
Proton pump: Complex IV
gets e- from cytochrome c and O2 is the final e- acceptor here. it also takes 4H+ from the matrix and pumps 2H+ into the inner membrane space from the matrix and uses the other two to reduce O2 to H2O
where does the TCA cycle occur?
mitochondrial matrix
where does oxidative phosphorylation occur?
in the inner membrane space
Complex II
Succinate dehydrogenase
succinate-CoQ reductase
forms fumarate from succinate and also generates ubiquinole (reduced form of ubiqunone) and transfers those e-
this complex is especially important if you have a complex I deficiency cause you might be able to bypass complex 1 in order still make ATP (youd just wanna stay away from a ton of carbs but youd want protein/fatty acids so you can form succinate straight away)
megacomplexes
mitochondrial respiratory complexes can form megacomplexes that have I,III,IV all attached together and another megacomplex that has I,II,III, and IV attached.
this supercomplex allows for efficient transfer of e- and pumping of protons
-important for quick energy demand
Ubiquinone/ubiquinol pool
can be fed into from Complex I or II which then goes to complex III which goes to cytochrome c which goes to complex IV which gives the e- to O2