ETC Flashcards
where does ECT take place
inner mito mem
what are the primary moles used to achieve oxidative phosphorylation
NADH and FADH2. this moles are e- carriers which are used to reduce oxygen to water
what is the reduction potential
the willingness for electrons to move from one mole to another
positive vs negative reduction potential
P= the oxidized form of a sub holds a high e- affinity than does H2 (happy to accept the e-, like O2)
N=the oxidized form of a sub holds a lower e- affinity than does H2 (wishing to get rid of e-, like NADH)
does FADH2 or NADH feed into the chain first? why? which complex does it go to?
FADH2 bc it has a lower reduction potential (is more willing to hold onto its e- than NADH, so give it to the portion complex that wants it the most)
it is fed into complex 2 (succinate-Q-reductase)
how do the complexes take on the e-?
via the presence of a Fe based or Cu based heme group. the metal ino will take on the e- until it needs to be released
what is ubiquinone
a hydrophobic molecules that shuttles e- and h+ in the mito membrane. this mole can exists in many different states:
radial (holds one e- only)
semiquinone (holds one e- and one H+)
ubiquitol (fully reduced)
these states exists as a pool
where do the e- from NADH enter
complex 1 and ultimately into Q where Q is fully reduced to its ubiquitol form. the energy of the reduction of Q to Q2- pumps 4H+ from the matrix into the mitochondrion.
explain how the e- from FADH2 enter the ETC
FADH2 is proced by succinate dehydrogenase in the CAC. this enzyme belong to a larger complex (complex 2) where the FADH formed doesn’t leave the complex, but is instead shuttled over the ETC where the e- are donated to Q.
note that not H+ are transferred during this process
what is the purpose of complex 3
to transfer the e- in Q2- (via Fe) Cyt c and pump 2 proton from the matrix into the mitochondrion
what is Cyt c
a water-soluble protien that can only carry one e-
why is the Q cycle needed for the e- transfer from complex 3 to cyt c?
cyt c can only take one e- at a time.
how does the Q cycle work
2 QH2 moles bind to complex 3. total of 4 e- and 4 H+ (into intermem space) are released. the binding of QH2 allows 2 e- to move to 2 different parts of the enzyme. One e- goes to c1 and the other to b1. The e- in c1 enters cyt c, fully reducing allowing it to detect from the complex.
the other e passes into the Qi location where another Q awaits and takes up this e- to. form a radical.
the second QH2 follows the same manner, but the radical formed pumped 2 additional hydrogens from the matrix and reforms a QH2.
what is the net result of the q cycle at complex 3
4 protons released into intermembrane space (by 2nd QH2)
2 protons are removed from the matrix (by first QH2)
what happens at complex 4
4 e- are shuttled to O2 to form 2 H2O moles. followed by the pumping of protons from the matrix into the inner membrane.
how is O2 reduced to H2O
1) the e- from 2 cyt c moles pass through Fe and Cu ions in complex 4. Effectively Fe and CuB are reduced.
2)the reduced ions bind with O2 to form a peroxide bridge
3) 2 more e- enter the complex via attachment of 2 more cyt c. these e- draws in 2 H+ which together cleave the peroxide bond to make 2 hydroxyl groups
4) 2 more H+ enter the complete to from a good hydronium LG, which releases 2 moles of H2O and 4 oxidized Cyt c.
note that additional energy released from this process pumps an extra 4 H= from the matrix into the mito.
what is the proton motive force
a mechanism that utilizes the proton gradient formed during the ETC to synth ATP.
H+ passed though the ATP synthase
describe the three regions of the ATP synthase active site
all at the B positions
O L and T
T has a high affinity and will not release anything bound to it
O is the open slot that allows for the release of ATP
L loose stage which allows ADP to enter the complex again
the complex rotates counterclockwise
describe the mechanics of the proton motor force: how H+ is able to pass through
H+ enters the subunit, where a half channel exists. the H+ binds to glutamic acid which promotes the movement of the hydrophobic proton into the hydrophilic c-ring.
once H+ is attached, the c ring rotates one position clockwise. this inturn moves another H+ into a second half channel in the A subunit. this H+ is passed into the ATP synthase
What is the yield of ATP after the ETC
Approx 30 moles of ATP for one mole of glucose
How many moles of ATP come from cytoplasmic NADH and FADH2? Of the G3P shuttled NADH?
NADH= 2.5
FADH2= 1.5
Shuttled =1.5
When are electron effectively transferred to O2
Only when ADP is reduced into ATP
