Chapter 20 - The ETC

Question 1

oxidative phosphorylation

Answer 1

metabolic pathway that uses energy released by the oxidation of nutrients to produce ATP

Question 2

oxidative phosphorylation occurs in…

Answer 2

inner membrane of mitochondria

Question 3

final electron acceptor

Answer 3

O2

Question 4

electron donors

Answer 4

NADH and FADH2

Question 5

4 parts of the mitochondria

Answer 5

• outer membrane
• inner membrane
• intermembrane
• matrix

Question 6

Is the outer or inner membrane permeable to small molecules/ions?

Answer 6

outer; inner requires specific transporters

Question 7

chemiosmotic theory

Answer 7

• energy is released as electrons flow through the electron transport chain, energy is used to transport protons across the inner mito. membrane
• this generate potential energy, pH gradient and electrochemical potential across the inner mito. membrane
• protons flow back across the membrane down this gradient, through ATP synthase
• ADP + Pi –> ATP

Question 8

electron carriers of the ETC

Answer 8

• NADH and FADH2
• Ubiquinone (coenzyme Q)
• cytochromes (a,b,c)
• iron-sulfur centre-containing proteins

Question 9

ubiquinone (coenzyme Q)

Answer 9

• lipid soluble
• diffusible in lipid bilayer
• shuttles e- between less mobile e- carriers in a membrane
• accepts 1 or 2 e-

Question 10

cytochromes

Answer 10

proteins that function as electron carriers

Question 11

cytochrome c

Answer 11

• soluble protein
• carries one e-
• associates with outer surface of inner mito. membrane

Question 12

heme

Answer 12

prosthetic group of cytochromes (carry the e-)

-iron present as oxidized (FE3+) or reduced (Fe2+)

Question 13

How are electrons passed in heme?

Answer 13

they are passed by the reduction of Fe3+ to Fe2+, back to Fe3+

Question 14

proteins with iron-sulfur centers

Answer 14

2 iron atoms joined by 2 atoms of inorganic sulfur, linked to a protein by the amino acid cysteine.

Question 15

One protein can have ______ iron-sulfure centers.

Answer 15

several

Question 16

Proteins associated with ETC Complex I

Answer 16

NADH dehydrogenase; Fe-S proteins

Question 17

Proteins associated with ETC Complex II

Answer 17

Succinate dehydrogenase, Fe-S proteins

Question 18

Proteins associated with ETC Complex III

Answer 18

Cytochrome C oxidoreductase, Fe-S proteins

Question 19

Proteins associated with ETC Complex IV

Answer 19

cytochrome oxidase; Cu-S (cos) proteins (similar to Fe-S protein centers)

Question 20

Complex I: NADH dehydrogenase

Answer 20

• several Fe-S centers
• L shaped, one arm in matrix (N side), one in the membrane (P side)
• rxn: 2 e- reduction by by ubiquinone

Question 21

Complex II: Succinate Dehydrogenase

Answer 21

• oxidizes succinate to fumarate, transfers e- to ubiquinone –> QH2
• e- of from succinate –> FAD –> Fe-S centers –> ubiquinone –> reduce it to QH2 (ubiquinol)
• no H+ are moved across inner mito. membrane

Question 22

Complex III: Cytochrome C oxidoreductase

Answer 22

• present in inner mito. membrane
• transfer e- from ubiquinone –> cytochrome C
• transports protons from matrix to inter membrane space
• contributes to proton gradient N side

Question 23

Complex IV: cytochrome c oxidase

Answer 23

• integral membrane protein, inner mito. membrane
• carries e- from cyt c to O2, which is reduced to water
• pumps H+ across the membrane
• O2 is the final e- acceptor (requires 4 e-)

Question 24

Proton Motive Force

Answer 24

energy conserved from the electrochemical gradient created from movement of protons during e- transfer

Question 25

2 components of proton motive force

Answer 25

chemical potential energy and electrical potential energy

Question 26

chemical potential energy

Answer 26

a difference in proton conc. (a pH gradient)

Question 27

electrical potential energy

Answer 27

difference in electrical charge across the membrane, with the N side having a neg. charge

Question 28

What provides the necessary energy for ATP synthesis?

Answer 28

the flow of protons down their electrochemical gradient