Oxidative Phosphorylation

Question 1

mitochondria membranes and compartments

Answer 1

outer memb – permeable due to presence of porin
inner memb – impermeable, has metabolite transporters, folded into series of cristae, site of OxPhos

intermembrane space
inner matrix — site of TCA cycle and FA oxidation

Question 2

mitochondrial genome

Answer 2

have their own DNA, encoding for 13 of its own proteins

mito DNA is maternally inherited

Question 3

overview of OxPhos

Answer 3

generates NADH and FADH2

—these high nrg electrons flow thru 4 protein complexes called ETC

Question 4

a successful OxPhos must accomplish the following key goals?

Answer 4

1. transfer e- from NADH and FADH2 to O2

2. to establish a proton gradient across the inner mito memb to synthesize ATP

Question 5

electrons are transferred from NADH to O2 via ?

Answer 5

3 large protein complexes

• -NADH Q oxidoreductase complex I
• -Q cytochrome c oxidoreductase complex III
• -cytochrome c oxidase complex IV

(complex II - succinate Q reductase )

Question 6

co-enzyme Q aka ubiquinone

Answer 6

transfers e-‘s from NADH Q oxidoreductase
and
the succinate Q reductase to Q cytochrome c oxidoreductase

coenzyme Q has long tail made of 5 c isoprene units which makes it hydrophobic

Question 7

cytochrome c

Answer 7

shuttles e-‘s from Q cytochrome c oxidoreductase to cytochrome c oxidase

final component of ETC

catalyzes reduction of O2

Question 8

list components of ETC in order

Answer 8

1. NADH-Q oxidoreductase
2. succinate-Q reductase bound to ubiquinone (coenzyme)
3. Q-cytochrome c oxidoreductase
4. cytochrome c
5. cytochrome c oxidase

Question 9

complex I

Answer 9

NADH dehydrogenase or NADH-Q oxidoreductase

encoded by nuclear and mito genes

1st point of entry of e-‘s from NADH

Question 10

iron sulfur clusters

Answer 10

present in iron sulfur proteins

• -role in reduction rxns
• -undergoes redox rxns but the protons never leave the protein

example: NADH-Q oxidoreductase contains both 2Fe-2S and 4Fe-4S clusters

Question 11

complex II

Answer 11

FADH2 enters ETC thru complex II = succinate-Q reductase
—this connects ETC to OxPhos

FADH2 does not leave the complex
its e-‘s transferred to FeS and then to Q to form QH2

Question 12

complex III

Answer 12

e-‘s from QH2 are passed on to cytochrome c by cytochrome c oxidoreductase = complex III

flow of e-‘s thru this complex leads to transport of 2 protons to cytoplasmic side

Question 13

complex IV

Answer 13

= cytochrome c oxidase

this catalyzes transfer of e-‘s from reduced cyt c to O2 the final e- acceptor

4 e-‘s funneled to O2 to reduce it to water

Question 14

free radicals

Answer 14

partial reduction of O2 generates highly reactive Oxygen derivatives, called reactive oxygen species ROS

include superoxide ion, peroxide ion, hydroxyl radical

Question 15

antioxidants

Answer 15

superoxide dismutase SOD
catalase
glutathione peroxidase
vit E
vit C

Question 16

mechanism of action of SOD

Answer 16

SOD1 = Cu/Zn cytosolic
SOD2 = Mn/Zn mito