Electron Transport Chain

Question 1

Molecules Involved in e- Transfer

Answer 1

NAD+/NADH, FAD/FADH2, FMN, ubiquinone (Q or Coenzyme Q), cytochromes, iron-sulfur complexes, oxygen

Question 2

Ubiquinone (Q or Coenzyme Q)

Answer 2

small e- shuttle

Question 3

Cytochrome C

Answer 3

• heme containing proteins
• transfers e- from complex III to complex IV
• carries 1 e-, QH2 transfers 2e-
• one e- is transferred to cyt C and the other is
  put on another Q (semi-ubiquinone) which is
  filled by another incoming QH2

Question 4

Iron-Sulfur Complexes

Answer 4

Fe associated with Sulfur

Question 5

Chemiosmotic Theory

Answer 5

1. reduced substrate donates e-
2. e- carriers pump H+ out as e- flow to O2
3. electrochemical potential drive ATP synthesis via ATP synthase

Question 6

Flow of Electrons

Answer 6

1. e- from NADH passed from complex I or II to
   Q
2. reduced Q is a mobile carrier of e- to
   complex III
3. cytochrome C shuttles e- to complex IV
4. complex IV passes e- to O2, making H2O

Question 7

Complex I

Answer 7

• e- from NADH to FMN, Fe-S clusters, Q
• 4 H+ pumped out of matrix
• 2 e- and 2 H+ transfered to Q to manke QH2

Question 8

Complex II

Answer 8

• succinate dehydrogenase
• e- from FADH2 to Fe-S clusters (3), Q
• no H+ pumped
• e- transfered to QH2

Question 9

Complex III

Answer 9

• has 2 Q binding sites
• e- from QH2 to Fe-S clusters, heme, cyt C
• cyt C carries only 1 e-, QH2 donates 2 e-

Question 10

Complex IV

Answer 10

• cyt C delivers e- one at a time to heme,
  copper and O2
• 4 H+ are pumped out (1 H+ per e-), e- meet
  final destination producing H2O

Question 11

ETC Summary

Answer 11

complex I => complex II
- 1 NADH + 11 H+ (N) + 1/2 O2 => NAD+ + 10H+
(P) + H2O
complex II => complex IV
- FADH2 + 6 H+ (N) + 1/2 O2 => FAD + 6 H+ (P)
+ H2O

Question 12

ATP Synthase Complex Mechanism

Answer 12

1. H+ enters causing rotation of F0
2. rotation causes conformational change in α
   and β subunits
3. conformational changes catalyze ATP
   formation

Question 13

F1 Subunit

Answer 13

nine subunits

• 3 α/β dimers
• γ subunit (axle)
• δ subunit links F1 and F0
• ε subunit forms base

Question 14

Binding Exchange Model

Answer 14

• 3 subunits: one empty, one has ADP + Pi, one
  has ATP
• H+ translocation causes rotation and
  conformational change in all 3 α/β dimers
• ATP released from site when ADP + Pi are
  bound at another site
• each turn requires 9 H+ to make 3 ATP