11.2 Electron Transport Chain

Question 1

Glycolysis occurs in…

Answer 1

the cytosol

Question 2

Citrate cycle occurs in…

Answer 2

Mitochondrial Matrix

Question 3

ETS occurs in…

Answer 3

inner mitochondrial membrane

Question 4

What feeds the ETC?

Answer 4

NADH and FADH2

Question 5

What are the two routes of electron transport?

Answer 5

1. Oxidation of NADH on matrix side of IMM
2. Oxidation of FADH2 from either the cytosolic side or the matrix side of IMM

Question 6

What is the electron flow of NADH?

Answer 6

NADH → Comp I → Q → Comp III → Cyt c → Comp IV → O2

Question 7

How many protons are pumped across from NADH?

Answer 7

10 H+

Question 8

What is the electron flow from FADH2?

Answer 8

FADH2→ Comp II → Q → Comp III → cyt c → Comp IV → O2

Question 9

How many protons are pumped across from FADH2?

Answer 9

6 H+

Question 10

What facilitates ETC electron flow?

Answer 10

Electron carriers, ordered by increasing E

Question 11

What does Interruption of e- flow do?

Answer 11

inhibits ATP synthesis

Question 12

What are some Inhibitors of electron flow?

Answer 12

Rotenone (poison arrows, blocks ETS)
Hydrogen cyanide, CO, antimycin A

Question 13

Describe in general Complexes I, III, IV

Answer 13

Large multi-subunit complexes translocate protons across IMM

Question 14

What are the 3 membrane associated FAD/FADH2-containing enzymes?

Answer 14

(3 routes of FADH2 entry)
– Comp II (Succinate dehydrogenase)
– ETF-Q oxidoreductase - lipid metabolism
– Glycerol-3-phosphate dehydrogenase - cytosolic NADH

Question 15

What is Coenzyme Q?

Answer 15

ubiquinone
-Small hydrophobic e- carrier, diffuses through the membrane
-2 electrons: Comp I/II → Comp III

Question 16

What is Cytochrome c?

Answer 16

– Small water soluble protein in intermembrane space
– 1 electron: Comp III → Comp IV

Question 17

Complex I

Answer 17

NADH–ubiquinone oxidoreductase

Question 18

Complex II

Answer 18

succinate dehydrogenase

Question 19

Complex III

Answer 19

ubiquinone–cytochrome c oxidoreductase

Question 20

Complex IV

Answer 20

cytochrome c oxidase

Question 21

What are Protein-bound redox centers? What are the 3 types?

Answer 21

Bound to proteins in ETC
1. Iron-sulfur or copper centers (1 electron)
2. Hemes (1 electron)
3. Coenzymes FADH2 and FMN (1 or 2 electrons)

Question 22

What are the 2 Mobile electron carriers?

Answer 22

1. Coenzyme Q - small molecule, one or two electrons
2. Cytochrome C - small protein, one electron

Question 23

Describe Complex I

Answer 23

Largest of the 4 complexes (15-40 chains) M
Pumps 4 protons into intermembrane space
Oxidizes NADH
Reduces Q
FMN
Contains 7(+) Fe-S centers

Question 24

What are the three steps of electron flow of complex I?

Answer 24

1. NADH transfers 2 electrons to FMN
2. 2 electrons transferred from carrier to carrier
3. 2 electrons and 2 protons bind Q forming QH2
   (4 protons move from N to P side)

Question 25

What is the net result of Complex I?

Answer 25

Transfer of 2 e- from NADH to coenzyme Q 4 H+ translocated from matrix to the intermembrane space (P side)

Question 26

What is the net reaction from complex I?

Answer 26

NADH + Q + 5H+(N) ----> NAD+ + QH2 + 4H+(P)

Question 27

What are things about Coenzyme Q?

Answer 27

1. Mobilee-carrier – Comp I or II —> Comp III 2. Entry point for e- pairs into ETS - From CC, fatty acid oxidation, or G3P dehydrogenase 3. 1 or 2 electrons – Adapter b/w 2e- to 1e- carriers, Q cycle

Question 28

Describe Complex II

Answer 28

● Also catalyzes step 6 in citrate cycle – FAD→FADH2 (1 or 2 electrons) ● 3 Fe-S centers and b-type heme – 1electron ● Q→QH2 – 1 or 2 electrons

Question 29

Complex II net result

Answer 29

Oxidizes of FADH2 to FAD Reduces Q to QH2 No translocation of H+

Question 30

Complex II net reaction

Answer 30

FADH2 + Q —> FAD + QH2

Question 31

Describe Complex III

Answer 31

Dimeric complex (11 subunits per monomer) ● Pumps 4 protons into intermembrane space ● 2 Fe-2S centers, 2 b-type & 1 c-type heme – 1electron ● Oxidizes QH2 – 1 or 2 electrons – Q-cycle ● Reduces Cyt C – 1 electron

Question 32

Complex III net result

Answer 32

Transfer 2e- from QH Translocation of 4H+ to intermembrane space

Question 33

Complex III net reaction

Answer 33

QH2 + 2H(N) + 2 Cytochrome C (oxidized) --> Q + 4H+(P) + 2 Cytochrome C (reduced)

Question 34

What is the Q cycle?

Answer 34

* Occurs in Comp III * Converts 2 e- transfer to 1 e-

Question 35

What are the 4 steps of the Q cycle?

Answer 35

1. Oxidation of QH2 at Q(P) - electron goes to cytochrome C 2. Oxidized Q goes to Q(N) 3. New QH2 binds to QP, is oxidized, election goes to a new cytochrome c 4. 2nd electron from step 3 reduced semiquinone QN and 2 protons reform QH2