Lecture 29

Question 1

What are the two reactions coupled to produce oxidative phosphorylation?

Answer 1

The electron transport chain and ATP synthase

Question 2

What are the two reactions coupled by?

Answer 2

A proton gradient

Question 3

What is the electron transport chain?

Answer 3

The process where electrons from NADH2 and FADH are passed through a series of carriers, to pump protons into the intermembrane of the mitochondria and create a H+ gradient

Question 4

Where is the electron transport chain?

Answer 4

On the inner membrane of the mitochondria

Question 5

How do we know the ETC is in the inner membrane?

Answer 5

Isolated mitochondria were treated with a strong and mild detergents to solubilise all and only the outer membranes respectively. When there are no membranes, the ETC does not work. Then there is no outer membrane, the ETC does work. Therefore the ETC is situated on the inner membrane

Question 6

What is the ETC organised into?

Answer 6

Four complexes labeled I to IV

Question 7

What does each complex contain?

Answer 7

Multiple carriers

Question 8

What are the two mobile carriers?

Answer 8

UQ and cyt c

Question 9

What happens to each carrier in the ETC?

Answer 9

Each accepts electron(s) to be reduced in one redox reaction and then donates electron(s) to be oxidised in another redox reaction

Question 10

What happens to electrons as they move through the carriers?

Answer 10

As electrons move to carriers with a higher reduction potential energy is released

Question 11

Is the ETC energetically favourable to unfavourable?

Answer 11

Favourable

Question 12

What is the energy released as electrons move down the ETC used for

Answer 12

To move protons across the mitochondrial membrane

Question 13

What is the path of NADH through the ETC?

Answer 13

Complex I → UQ → Complex III → Cyt c → Complex IV → O2

Question 14

What is the path of FADH2 through the ETC?

Answer 14

Complex II → UQ → Complex III → Cyt c → Complex IV → O2

Question 15

What are the two inhibitors of electron flow through the ETC?

Answer 15

Rotenone, Cyanide and carbon monoxide

Question 16

How does rotenone inhibit electron flow?

Answer 16

Inhibits electron transfer from complex I to UQ

Question 17

How does cyanide inhibit electron flow?

Answer 17

Binds to a carrier in complex IV

Question 18

How does carbon monoxide inhibit electron flow?

Answer 18

It binds where O2 is supposed to bind

Question 19

Overall, how does inhibition prevent ATP synthesis?

Answer 19

Stopped electron flow means no proton gradient can be formed and no ATP is made. Coenzymes also build up, so there is no oxidising power for other pathways

Question 20

What is the electron flow through complex I?

Answer 20

NADH is oxidised, 2 e- are released into ETC, 4 protons are pumped for each NADH oxidised

Question 21

What is the electron flow through complex II?

Answer 21

FADH2 is oxidised (SDH reaction is shared with the CAC), 2 electrons released into ETC, no protons pumped

Question 22

What is the electron flow through UQ?

Answer 22

Complex I and II both pass 2 electrons to UQ, UQ can move within the inner mitochondrial membrane

Question 23

What is the electron flow through complex III?

Answer 23

Complex III releases 1 electron at a time to cyt c and pumps 4 protons across the inner membrane

Question 24

What is the electron flow through cyt c?

Answer 24

Cyt c moves on the outer surface of the inner membrane. Carries 1 electron at a time to complex IV

Question 25

What is the electron flow through complex IV?

Answer 25

Accepts 1 electron at a time from cyt c, reduced O2 to H2O. For 1 NADH/FADH2 - 2H+ pumped and 1/2O2 + 2H+ → H2O

Question 26

What happens to H2O synthesis biologically?

Answer 26

Complex IV waits until it has all 4 before synthesising H2O

Question 27

What is the energy accounting from NADH?

Answer 27

4(CI) + 4(CIII) + 2(CIV) = 10 H+

Question 28

What is the energy accounting from FADH2?

Answer 28

4(CIII) + 2(CIV) = 6 H+