Electron Transport Chain

Question 1

Oxidative phosphorylation

Answer 1

• Redox rxns
• Flow of e- from NADH and FADH2 to O2
• Proton gradient
• Synthesis of ATP

Question 2

Electron-transport chain = series of coupled redox rxns

Answer 2

The members of the ETC are arranged so that the e- always flow to components with a more positive reduction potentials (higher e- affinity)

Question 3

Complex 1: NADH-Q oxidoreductase

Answer 3

• Flow of 2 e- from NADH to coenzyme

- Pumps 4 H+ out of matrix

Question 4

Complex 2: Succinate-Q Reductase Complex

Answer 4

FADH2 e- are transferred to Fe-S centers than to Q for entry into the ETC

• DOES NOT transport protons!!
• Less ATP is formed from the oxidation of FADH2 than from NADH

Question 5

Complex 3: Q-cytochrome c oxidoreductase

Answer 5

Electrons flow from Ubiquinol (QH2) to Cytochrome c through Q-cytochrome c oxidoreductase, then to cytochrome c (Cyt C)

Question 6

QH2 passes 2 e- to Q-cytochrome c oxidoreductase, but the acceptor of this complex, cytochrome c, can accept only 1 e-

Answer 6

QH2 + Q + cyt c(ox) -> Q + Q-* + 2H+ + cyt c (red)

QH2 + Q-* + 2H+ + cyt c (ox) -> Q + 2H+ + QH2 + cyt c (red)

Question 7

Complex 4: cytochrome c oxidase

Answer 7

Catalyzes the transfer of e- from the reduced form of cytochrome c to O2
4Cyt c (red) + 8H+(matrix) -> 4Cyt c (ox) + 2H2O + 4H+(intermembrane space)

Question 8

The ETC is also a source of

Answer 8

reactive O2 species