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BIOC192 > Lecture 32: ELECTRON TRANSPORT CHAIN > Flashcards

Lecture 32: ELECTRON TRANSPORT CHAIN Flashcards

1
Q

What is oxidative phosphorylation?

A

The coupled process of electron transport through the electron transport chain (ETC) and the phosphorylation of ADP to ATP by ATP synthase

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2
Q

What are the ETC and ATP synthesis coupled by?

A

A proton gradient

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3
Q

What makes the proton gradient?

A

The ETC

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4
Q

What uses the proton gradient?

A

ATP synthase

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5
Q

Where does the ETC occur?

A

In the inner mitochondrial membrane

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6
Q

What does the inner mitochondrial membrane provide?

A

A barrier to form the proton gradient

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7
Q

Where are reduced coenzymes found?

A

Mainly in the matrix

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8
Q

What must be used to extract mitochondria from cells?

A

Tissue high in mitochondria such as liver

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9
Q

What is first done with the tissue?

A

Homogenisation in buffered solution to get homogenate

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10
Q

What is done with homogenate?

A

Centrifuge at 1000 xg to get debris and nuclei (heavy at bottom) and supernatant

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11
Q

What is done with the supernatant?

A

Centrifuge at 7000xg to get a pellet of mitochondria at the bottom and a supernatant of membranes, ribosomes and cytoplasm on top

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12
Q

What happens when extracted mitochondria are treated with strong detergent?

A

All membranes are solubilised and the ETC doesn’t work

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13
Q

What happens when extracted mitochondria are treated with mild detergent?

A

Only the outer membrane is removed and the ETC still works

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14
Q

What happens in the ETC?

A

Electrons are passed through a series of carriers

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15
Q

Where are the electrons in the ETC from?

A

NADH and FADH2 (they are oxidised)

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16
Q

What do the electrons do in the ETC?

A

Reduce oxygen to water

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17
Q

What is the terminal electron acceptor of the ETC?

A

Oxygen

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18
Q

What happens as electrons are transported through the ETC?

A

Protons are pumped

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19
Q

How many complexes are in the ETC?

A

Four (I to IV)

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20
Q

What does each complex contain?

A

Multiple carriers (carriers are organised into complexes)

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21
Q

How many mobile carriers in the ETC?

A

Two

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22
Q

What are the two mobile carriers?

A

Ubiquinone (UQ)/CoenzymeQ (CoQ) and cytochrome C (CytC)

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23
Q

What does movement of electrons involve?

A

Carriers undergoing a series fo redox reactions

24
Q

what does each carrier do?

A

Accept electron(s) (is reduced) in one redox reaction and then donates electron(s) (is oxidised) in another redox reaction

25
Q

Where do electrons move?

A

To carriers with a higher reduction potential (oxygen has the highest reduction potential)

26
Q

What happens as electrons move between carriers?

A

Energy is releases (delta g is negative)

27
Q

What is the energy released used for?

A

To translocate protons across the inner mitochondrial membrane to the intermembrane space

28
Q

What is the path that electrons from NADH take?

A

Complex 1 > UQ > Complex 3 > Cyt c > Complex 4 > Oxygen

29
Q

What is the path that electrons from FADH2 take?

A

Complex 2 > UQ > Complex 3 > Cyt c > Complex 4 > Oxygen

30
Q

What happens at complex 1?

A

NADH is oxidised and two electrons are released into the ETC

31
Q

How many protons are pumped at Complex 1?

A

Four protons for each NADH oxidised

32
Q

What happens at complex 2?

A

FADH2 is oxidised and two electrons are released into the ETC

33
Q

What reaction happens at Complex 2?

A

The SDH reaction which is shared with the citric acid cycle

34
Q

How many protons are pumped at complex 2?

A

None

35
Q

What do complex 1 and 2 both do?

A

Pass two electrons to UQ/CoQ

36
Q

What can UQ do?

A

Move within the inner mitochondrial membrane

37
Q

What is UQ?

A

A coenzyme (not from a vitamin) which can exist in reduced and oxidised forms

38
Q

What does Co-Q undergo?

A

Tow-electron redox reactions (like NADH and FHAD2) but can accept or release one electron at a time

39
Q

Where does Co-Q release electrons?

A

One at a time to Complex 3 by the Q-cycle

40
Q

What does Complex 3 do?

A

Release one electron at a time to cytochrome c

41
Q

How many protons are pumped at complex 3?

A

Four (1 coenzyme=2 electrons)

42
Q

Where does cytochrome c move?

A

On the outer surface of the inner mitochondrial membrane

43
Q

What does cytochrome c do?

A

Carry one electron at a time from complex 3 to complex 4

44
Q

What is cytochrome c?

A

A haem containing protein

45
Q

How does chytochrome c carry its electron?

A

Via reversible Fe2+/Fe3+ redox reactions

46
Q

What does Complex 4 do?

A

Accepts one electron at a time from cytochrome c and reduces oxygen to water

47
Q

How many protons pumped at complex 4 per 1 NADH/FADH2?

A

2

48
Q

What is the reaction per 1 NADH/FADH2 at complex 4?

A

1/2O2 + 2H+&raquo_space;> H20

49
Q

What is the biological reaction at complex 4?

A

it waits until it has four electrons (oxidation of two coenzymes): O2 + 4H+&raquo_space; 2H2O

50
Q

What are some inhibitors of electron movement through the ETC?

A

Rotenone, cyanide and carbon monoxide

51
Q

What does rotenone do?

A

Inhibits electron transfer from complex 1 to Co-Q

52
Q

What does cyanide do?

A

Binds to a carrier in complex 4

53
Q

What does carbon monoxide do?

A

Binds where oxygen binds

54
Q

What is the effect if inhibiting electron movement?

A

Stops the flow of electrons through the ETC, no proton gradient is formed (ATP not made), build up of reduced coenzymes (NADH and FADH2) so no oxidising power for other pathways and reactive oxygen species which are damaging are produce

55
Q

How may protons pumped per NADH?

A

4+4+2=10

56
Q

How many protons pumped per FADH2?

A

4+2=6

BIOC192 (38 decks)

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