Oxidative phosphorylation

Question 1

In oxidative phosphorylation what acts as proton carriers?

Answer 1

Reduced cofactors

Question 2

What occurs at complex I?

Answer 2

• electrons pass from NADH to Flavin mononucleotide
• then to a series of FeS centres

Question 3

What is complex I also known as?

Answer 3

NADH dehydrogenase

Question 4

For 1 NADH how many H+ are pumped into the intermembrane space?

Answer 4

4

Question 5

What protein makes up complex II?

Answer 5

Succinate dehydrogenase

Question 6

Outline the structure of succinate dehydrogenase

Answer 6

• multi-subunit protein
• Fe-S centres
• Heme group

Question 7

Where does FADH₂ enter the respiratory chain?

Answer 7

Complex II

Question 8

What is the purpose of ubiquinone?

Answer 8

It is a shuttle for electrons between complex I and II and complex III

Question 9

What is the structure of ubiquinone?

Answer 9

Lipid soluble

Question 10

What is the purpose of complex III?

Answer 10

Transfers electrons from ubiquinone to cytochrome C

Question 11

What is the structure of complex III?

Answer 11

Large membrane spanning multi-subunit complex

Question 12

As electrons move through complex III how many H+ are pumped into the intermembrane space?

Answer 12

4H+

Question 13

What are the electron transfer components in complex III?

Answer 13

• Cytochrome b
• Fe-S centres
• Cytochrome C₁

Question 14

What prosthetic group do cytochromes contain?

Answer 14

Heme

Question 15

What is the role of cytochrome c?

Answer 15

Shuttles electrons between complexes III and IV

Question 16

What are the structures of cytochromes?

Answer 16

• contain heme
• soluble protein in intermembrane space
• Small

Question 17

Where is cytochrome c found?

Answer 17

the interembrane space

Question 18

What protein is in the complex IV?

Answer 18

Cytochrome Oxidase

Question 19

What is the role of complex IV?

Answer 19

Transfers electrons from cytochrome c to molecular oxygen, the result of which is reduction to water

Question 20

How many H+ are pumped into the intermembrane space by complex IV?

Answer 20

2 H+

Question 21

What are the electron transfer components of complex IV?

Answer 21

• Cytochrome a
• Cytochrome a₃
• 2 Copper atoms

Question 22

What is a standard redox potential?

Answer 22

The measure of the tendency of a redox couple to give up electrons

Question 23

What is a redox couple?

Answer 23

The oxidised and reduced forms of a component

Question 24

What does a more positive standard redox potential mean in terms of tendency to accept electrons?

Answer 24

More positive srp means greater tendency to accept electrons and smaller tendency to give up electrons

Question 25

What is the evidence that the respiratory chain and ATP synthase are separate systems linked by the proton motive force?

Answer 25

* uncouplers dissipate the H+ gradient and abolish ATP synthesis

Question 26

Give an example of an uncoupler

Answer 26

2,4-DNP

Question 27

How does 2,4-DNP act as an uncoupler?

Answer 27

By providing a means for H+ to be shuttled across the membrane so there is no proton gradient

Question 28

What blocks complex IV?

Answer 28

CN- or CO

Question 29

Which complex does rotenone inhibit?

Answer 29

Complex I

Question 30

Which complex does antimycin A inhibit?

Answer 30

Complex III

Question 31

What does oligomycin inhibit?

Answer 31

ATP synthase

Question 32

How is ATP synthesised by ATP synthase?

Answer 32

* H+ movement causes the protein stalk to rotate within the headgroup, changing the conformation of β subunits * β subunits bind ATP and Pi

Question 33

How is ATP released from the β subunits of ATP synthase?

Answer 33

By the H+ driven conformational change

Question 34

How does the movement of the γ subunit force a conformational change in the α and β subunits?

Answer 34

It is an asymmetric protein

Question 35

How many H+ are required to synthesize 1 ATP?

Answer 35

4

Question 36

How many ATPs are made from NADH oxidation?

Answer 36

2.5

Question 37

How many ATPs are made from FADH₂ oxidation?

Answer 37

1

Question 38

How many ATP can be synthesized from 1 turn of the citric acid cycle?

Answer 38

10

Question 39

What does mitochondrial DNA code for?

Answer 39

13 subunits of the electron transport chain and ATP synthase

Question 40

What are the features of brown adipose tissue?

Answer 40

it contains many mitochondria and many small triacylglycerol droplets

Question 41

What protein does the inner mitochondrial membrane of brown adipose tissue contain lots of?

Answer 41

Thermogenin (UCP1)

Question 42

What is the purpose of UCP1?

Answer 42

It acts as a proton channel and short circuits the proton gradient

Question 43

Which hormone stimulates brown adipose tissue?

Answer 43

Noraderenaline