ETC

Question 1

where does ECT take place

Answer 1

inner mito mem

Question 2

what are the primary moles used to achieve oxidative phosphorylation

Answer 2

NADH and FADH2. this moles are e- carriers which are used to reduce oxygen to water

Question 3

what is the reduction potential

Answer 3

the willingness for electrons to move from one mole to another

Question 4

positive vs negative reduction potential

Answer 4

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)

Question 5

does FADH2 or NADH feed into the chain first? why? which complex does it go to?

Answer 5

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)

Question 6

how do the complexes take on the e-?

Answer 6

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

Question 7

what is ubiquinone

Answer 7

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

Question 8

where do the e- from NADH enter

Answer 8

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.

Question 9

explain how the e- from FADH2 enter the ETC

Answer 9

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

Question 10

what is the purpose of complex 3

Answer 10

to transfer the e- in Q2- (via Fe) Cyt c and pump 2 proton from the matrix into the mitochondrion

Question 11

what is Cyt c

Answer 11

a water-soluble protien that can only carry one e-

Question 12

why is the Q cycle needed for the e- transfer from complex 3 to cyt c?

Answer 12

cyt c can only take one e- at a time.

Question 13

how does the Q cycle work

Answer 13

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.

Question 14

what is the net result of the q cycle at complex 3

Answer 14

4 protons released into intermembrane space (by 2nd QH2)

2 protons are removed from the matrix (by first QH2)

Question 15

what happens at complex 4

Answer 15

4 e- are shuttled to O2 to form 2 H2O moles. followed by the pumping of protons from the matrix into the inner membrane.

Question 16

how is O2 reduced to H2O

Answer 16

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.

Question 17

what is the proton motive force

Answer 17

a mechanism that utilizes the proton gradient formed during the ETC to synth ATP.

H+ passed though the ATP synthase

Question 18

describe the three regions of the ATP synthase active site

Answer 18

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

Question 19

describe the mechanics of the proton motor force: how H+ is able to pass through

Answer 19

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

Question 20

What is the yield of ATP after the ETC

Answer 20

Approx 30 moles of ATP for one mole of glucose

Question 21

How many moles of ATP come from cytoplasmic NADH and FADH2? Of the G3P shuttled NADH?

Answer 21

NADH= 2.5
FADH2= 1.5
Shuttled =1.5

Question 22

When are electron effectively transferred to O2

Answer 22

Only when ADP is reduced into ATP