Week 6 Pt1

Question 1

Complex 1

Answer 1

Pumps 4 protons Take electrons from NADH and deliver it to ubiquinone

Question 2

Complex II

Answer 2

Pumps no protons Reduces the quinones We take protons from the negative side at complex II but we are not pushing it to the positive side Enzyme: succinate dehydrogenase Catalysed the transfer of electrons from succinate to FADH2 to ubiquinone (non transport of H+)

Question 3

Complex III

Answer 3

Called cytochrome bc1 because 2 cytochromes are present Transports 4 protons across Catalysed the transfer of electrons from ubiquinone to cytochrome c

Question 4

What do both complex I and complex II reduce?

Answer 4

Ubiquinone

Question 5

What is electron transfer accompanied by?

Answer 5

Translocation of H+ across the inner mitochondrial membrane

Question 6

Complex II is not a coupling site

Answer 6

No structural rearrangement It feeds electrons from succinate to IMM to reduce hydrophobic UQ to UQH2

Question 7

Complex III

Answer 7

H+ translocation is coupled to oxidation of U1H2 to UQ Transition from 2 electron carrier (UQH2) to 1 electron carrier (cyt C)

Question 8

How many quinone binding sites are there?

Answer 8

2 - one on the P side of the membrane and one is on N side of membrane

Question 9

Complex IV

Answer 9

Catalyses transfer of electrons from cytochrome C released from complex III to oxygen Proton pumping across the membrane

Question 10

How many electrons are required to reduce oxygen to water?

Answer 10

4 electrons

Question 11

What holds iron in place?

Answer 11

A combination of cysteine side chain
Cysteine sulfhydryl
Inorganic sulphur

Question 12

2 FE-S clusters

Answer 12

2 sulphurs do not include cysteine side chain

Just inorganic sulphur

Question 13

4 FE-S clusters and 3 FE-S clusters

Answer 13

Different stoichiometry

Question 14

Why is iron a limiting agent in biology?

Answer 14

It is not very accessible since the great oxygenation event

Fe2+ which is very bioacessible turned into Fe3+ which sank to the bottom of ocean

Question 15

How many Fe-S clusters in the respiratory chain?

Answer 15

12 sites

Question 16

What gives Fe-S clusters their redox potential?

Answer 16

Amino acids that surround them

Exposure to solvents

Question 17

What reaction do Fe-S clusters generally carry out?

Answer 17

Single-electron transfers

Question 18

Where is Fe-S found?

Answer 18

Complex I and II

Question 19

Where is copper found?

Answer 19

Complex IV

Question 20

What is oxygen consumption coupled to?

Answer 20

ATP synthesis

Question 21

Method of ETC

Answer 21

1. Set up oxygen electrode with 0.2ml purified mitochondria in 20ml solution as sample
2. Add 20 microlitre ADP
3. Inhibition is relieved by adding a substrate which enters after the inhibited complex

Question 22

Rotenone

Answer 22

Inhibits complex I
Inhibit the transfer of electrons from Fe-S cluster in complex I to ubiquinone
Inhibits oxidation of NADH —> NAD+
No PMF
ATP synthase isn’t getting sufficient H+ to flow through this - less ATP
Decrease in oxygen consumption
Rotenone has no effect on oxidation of either succinct or ascorbate

Question 23

What happens if there is no oxidation?

Answer 23

No transfer of electrons

No energy to pump the H+ ions from matrix into IMS

Question 24

Anitmycin A

Answer 24

Inhibits either complex 2 or 3
Bind to Qi site on cytochrome C reductase in complex 3
This inhibits the oxidation of ubiquinone In Qi site of ubiquinol
This won’t allow protons coming from NADH/FADH oxidation to go into complex 3
ETC decreased - decrease in oxygen consumption
Flow of H+ from Matrix to IMS is reduced
Flow of protons through ATP synthase decrease
ATP synthesis decreased

Question 25

Potassium cyanide

Answer 25

Inhibit complex 4
Bind to Iron in heme group of cytochrome oxidase C - associated with complex IV
Blocks transfer of electrons to oxygen
All complexes before that remain without an electron there is no passing of electrons down the chain and no PMF is established
Limited amount of ATP produced

Question 26

What does complex I Contain?

Answer 26

FMN containing flavoprotein - oxidise NADH
8 distinct Fe-S clusters
2 bound molecule of ubiquinone