lecture 32 - electron transport chain

Question 1

What processes are coupled together in oxidative phosphorylation?

Answer 1

Electron transport chain, phosphorylation of ADP to ATP by ATP-synthase

Question 2

How is the ETC and ATP-synthase coupled in oxidative phosphorylation?

Answer 2

Coupled by a proton gradient made by the ETC and used by ATP-synthase

Question 3

Where is the electron transport chain (ETC) located, and why?

Answer 3

In the mitochondria, as it requires oxygen. Specifically in the inner mitochondrial membrane

Question 4

Why is the ETC in a membrane?

Answer 4

To make a proton gradient, a barrier is required to stop proton diffusion.

Question 5

Where are the reduced coenzymes used in the ETC found?

Answer 5

The mitochondrial matrix

Question 6

How many complexes are there in the ETC?

Answer 6

4 (I, II, III, IV)

Question 7

What do the complexes within the ETC contain?

Answer 7

Multiple carriers each

Question 8

What are the 2 mobile carriers in the ETC?

Answer 8

CoQ and cyt C

Question 9

How do carrie’s facilitate electron transport in the ETC?

Answer 9

By undergoing a series of redox reactions - each carrier accepts electron(s) (is reduced) then donates electron(s) (is oxidised)

Question 10

What is released as electrons move through carriers in the ETC?

Answer 10

energy

Question 11

How is energy released in the ETC?

Answer 11

As electrons move to carriers with a higher reduction potential (until O2 which has the highest), energy is released

Question 12

What is the energy released in the ETC utilised for?

Answer 12

Translocation of protons across the mitochondrial membrane via the complexes

Question 13

What is the releative concentration of H+ in the mitochondrial matrix and intermembrane space?

Answer 13

Higher in inter membrane space, lower in the matrix

Question 14

Where are protons translocated from and to in the ETC?

Answer 14

From matrix to intermembrane space of mitochondria

Question 15

Where is NADH oxidised in the ETC?

Answer 15

Complex I

Question 16

How many electrons are released when NADH is oxidised at Complex I in the ETC?

Answer 16

2 e-

Question 17

How many protons are pumped when NADH is oxidised at Complex I in the ETC?

Answer 17

4H+ per NADH

Question 18

What is the path of electron flow from NADH in the ETC?

Answer 18

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

Question 19

What is the path of electron flow from FADH2?

Answer 19

FADH2 → Complex II → UQ → Complex III → Cyt c → Complex IV → O2

Question 20

Where is FADH2 oxidised in the ETC?

Answer 20

At complex II

Question 21

How many electrons are released when FADH2 is oxidised at Complex II in the ETC?

Answer 21

2 e-

Question 22

How many protons are pumped when FADH2 is oxidised at Complex II in the ETC?

Answer 22

No protons as not enough energy is released

Question 23

What reactions are happening at complex II in the ETC?

Answer 23

FADH2 is oxidised to FAD, Succinate is converted to fumarate using SDH (succinate dehydrogenase), in a shared reaction with the citric acid cycle

Question 24

What are the 2 forms that CoQ/UQ can exist in?

Answer 24

UQ and UQH2 (carrying 2 hydrogen atoms/reducing equivalents)

Question 25

How many electrons can CoQ/UQ accept or release at a time?

Answer 25

1 - pass to complex III from complex 1 or 2

Question 26

How many electrons are released from Complex III to cyt c and then to Complex IV at a time?

Answer 26

On electron at a time

Question 27

How many protons does complex III pump across the membrane per electron?

Answer 27

2H+ - 4 per coenzyme/2 electrons

Question 28

Where is cyt-c found in the ETC?

Answer 28

On the outer surface of the inner mitochondrial membrane (see exam diagram)

Question 29

What is the role of complex IV in the ETC?

Answer 29

Accepts one electron at a time from cyt c and reduces oxygen to water (1/2O2 + 2H+ -> H2O). Pumps 2H+ across membrane

Question 30

Although Complex IV receives one electron at a time, how does it wait before reducing oxygen to water?

Answer 30

Biologically, it waits until it has 4 electrons (has oxidised to 2 coenzymes) so that the reaction can proceed with one full mole of O2: O2 + 4H+ -> H2O

Question 31

How many protons are pumped in total from the oxidation of one NADH?

Answer 31

10 protons - 4(CI), 4(CIII), 2(CIV)

Question 32

How many protons are pumped in total from the oxidation of one FADH2?

Answer 32

6 protons - 4(CIII) + 2(CIV)