Electron Transport Chain

Question 1

How many ATP’s can be produced from NADH?

Answer 1

3

Question 2

How many ATP’s can be produced from FADH2

Answer 2

2

Question 3

Name the 3 integral complexes in the electron transport chain (in order)

Answer 3

NADH dehydrogenase complex
Cytochrome b-c1 complex
Cytochrome oxidase complex

Question 4

Name the 2 mobile electron carriers in the etc

Answer 4

Ubiquinone (Coenzyme Q)

Cytochrome C

Question 5

How is the unidirectional transport of electrons ensured?

Answer 5

Each complex has a higher affinity for electrons than the last.

Question 6

How does NADH dehydrogenase complex accept electrons?

Answer 6

It has a higher affinity for electrons than NADH.

It oxidises NADH liberating H+ and 2e-

Question 7

What is the purpose of the etc complexes?

Answer 7

To pump protons into the intermembrane space as they transport electrons

Question 8

How many electrons can Ubiquinone accept?

Answer 8

One or Two

Question 9

Which TCA-cycle enzyme is integral to the inner membrane and what is the significance of this to the ETC?

Answer 9

Succinate Dehydrogenase.

It produces FADH2 which passes its electrons directly to ubiquinone.

Question 10

Why does FADH2 produce less ATP than FADH in oxidative phosphorylation?

Answer 10

It bypasses NADH dehydrogenase complex, as FADH2’s electrons are transferred directly to ubiquinone and therefore less protons are pumped into the intermembrane space.

Question 11

How many electrons does Cytochrome oxidase accept?

Answer 11

4, requiring two NADHs to be oxidised

Question 12

What makes Oxygen a good terminal electron acceptor?

Answer 12

It has a very high affinity for electrons

Question 13

Describe the reaction that occurs at Cytochrome oxidase

Answer 13

4e- + 4H+ O2 –> 2H20

Question 14

How many protons does Cytochrome oxidase pump into the intermembrane space?

Answer 14

4

Question 15

Describe the structure of ATP synthase

Answer 15

Membrane bound F0 part
F1 part projecting into the matrix
F0 consists of: a, b and c subunits
F1 consists of: alpha, beta and gamma subunits

Question 16

Describe the mechanism of ATP synthase

Answer 16

As H+ passes from the intermembrane space it binds to the C subunit, all 12 of which rotate. This turns the gamma subunit which acts as an asymetrical axle. This rotation causes structural changes in the alpha and beta subunits which alter their affinity for ADP and ATP. Torsional energy from the rotation binds Pi to ADP.

Question 17

How many ATPs can ATPsynthase form at once?

Answer 17

3

Question 18

What happens in the proton gradients are reversed?

Answer 18

ATP synthase converts ATP to ADP in order to restore the proton gradient

Question 19

Describe the 2 gradients in the chemiosmotic theory

Answer 19

Membrane potential due to positive charge in the intermembrane space.
pH gradient due to more H+ in the intermembrane space.