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Cell Biology > Oxidative Phosphorylation > Flashcards

Oxidative Phosphorylation Flashcards

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1
Q

What happens during oxidative phosphorylation?

A

Electrons are transferred through electron carriers

Process generates a proton gradient for ATP synthase

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2
Q

Where does oxidative phosphorylation take place?

A

Inner mitochondrial membrane

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3
Q

More acidic in the ___________

A

Intermembrane space

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4
Q

What are 4 examples of electron carriers?

A
  • NAD and FAD
  • Ubiquinone/Coenzyme Q
  • Cytochromes
  • Iron-sulphur proteins
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5
Q

What are the properties of ubiquinone/coenzyme Q?

A
  • Fat-soluble so able to move through membrane

- Can accept 1 or 2 electrons

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6
Q

What are cytochromes?

A

Iron heme-containing proteins that act as an electron carrier

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7
Q

What are the 3 types of cytochromes involves in oxidative phosphorylation? Are they membrane-bound or soluble?

A
  1. A is membrane-bound
  2. B is membrane-bound
  3. C is soluble
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8
Q

What is the basic formation of iron-sulphur proteins?

A

Fe and S coordinates with 4 cysteine residues from a protein

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9
Q

Complex I: where are the electrons transferred?

A

NADH to ubiquinone

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10
Q

Structure of complex I

A
  • 42 polypeptide chains

- 6 iron-sulphur centres

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11
Q

What is formed at complex I and where does it diffuse to?

A

Ubiquinol diffuses to complex III

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12
Q

Complex II: where are the electrons transferred?

A

Succinate to ubiquinone

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13
Q

What happens at complex II?

A

Electron is removed from succinate and transferred to FAD then to ubiquinone to form ubiquinol

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14
Q

Complex III: where are the electrons transferred?

A

Ubiquinone to cytochrome c

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15
Q

What is the problem with the reaction at complex III and how is it overcome?

A

Cytochrome c can only accept 1 electron but ubiquinone donates 2 electrons so there’s a process called the Q cycle

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16
Q

What is the Q cycle?

A

1 electron is transferred to cytochrome c and the other electron is recycled through the complex forming semi-ubiquinone

17
Q

Complex IV: where are the electrons transferred?

A

Cytochrome c to O2

18
Q

What is the relation between the inter membrane space and complex I and IV?

A

4 protons are pumped into the inter membrane space

19
Q

What is formed at complex IV?

A

H2O

20
Q

During the formation of H2O in Complex IV of oxidative phosphorylation what is consumed? What is the significance of this?

A
  • 4 protons are consumed from inside the mitochondria

- This helps to amplify the proton gradient across the inner mitochondrial membrane

21
Q

What does ATP synthase act as a pore for?

A

Hydrogen ions

22
Q

What are the subunits of ATP synthase and what are their functions?

A

F1 - ATPase for formation

F0 - membrane-embedded portion which acts as a pore for protons to pass through to drive ATPase

23
Q

What makes up the F1 subunit?

A

ß units, present in 3 states

24
Q

What are the 3 states of the ß units?

A

Empty
ADP
ATP

25
Q

What is bound at each state of the ß units?

A

Empty - nothing bound
ADP - ADP and Pi bound, loose
ATP - ATP-bound, tight configuration

26
Q

How does the movement of protons through ATP synthase drive ATP formation?

A
  • As the protons pass through the F0 complex they cause the subunits to rotate by 1/3
  • Each 1/3 turn causes a conformational change in the Beta subunit of F1 ATPase
27
Q

What regulates oxidative phosphorylation?

A

ADP and ATP levels

28
Q

How is oxidative phosphorylation regulated at rest?

A

The proton motive force is high but due to high ATP levels

–> minimal flow of protons through ATP synthase and low transfer of electrons

29
Q

How is oxidative phosphorylation regulated during exercise?

A

ATP is consumed therefore ADP levels rise
–> proton movement through synthase discharging the proton motive force. Results in increase electron transfer to keep proton motive force

30
Q

What are the two types of inhibitors of oxidative phosphorylation?

A
  • Electron transport inhibitor

- Uncoupling agents

31
Q

Give an example of an electron transport inhibitor and how it works

A

Cyanide, stops carriers from receiving electrons

32
Q

Give an example of an uncoupling agent and how it works

A

2,4-Dinitrophenol, dissipates the proton gradient so have to work harder to make ATP

Cell Biology (21 decks)

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