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Biochem Take 2. > The Electron Transport Chain. > Flashcards

The Electron Transport Chain. Flashcards

1
Q

What is a prosthetic group?

A

These are organic in nature and not made of protein.

They are very tightly bound (usually covalently) to the enzyme.

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2
Q

What are prosthetic groups also known as?

A

A coenzyme.

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3
Q

Which step of aerobic respiration will generate the most ATP?

A

The ETC.

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4
Q

What is the final electron acceptor in the ETC?

A

Oxygen.

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5
Q

What is the goal of the ETC?

A

To produce energy in the form of ATP via the oxidation of NADH and FADH2.

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6
Q

Where in the cell does the ETC occur?

A

In the mitochondrial matrix and in the inner mitochondrial membrane.

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7
Q

Give a quick summary of the ETC?

A

Hydrogen atoms are stripped from NADH and FADH2 and transported into the inter membranous space.

This creates a proton gradient and the ions want to re-enter the mitochondrial matrix.

The ions can re-enter by passing through ATP synthase.

As each H+ ion passes through, one molecule of ATP is generated.

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8
Q

How many complexes are in the ETC?

A

4.

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9
Q

Where are the 4 complexes in the ETC found?

A

Embedded into the inner mitochondrial membrane.

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10
Q

What are the 4 complexes in the ETC?

A

Complex 1. The NADH dehydrogenase complex.

Complex 2 = Succinate dehydrogenase.

Complex 3 = Cytochrome reductase.

Complex 4 = Cytochrome oxidase.

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11
Q

What are the 2 mobile electron carriers in the ETC?

A

Co-enzyme Q.

Cytochrome C.

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12
Q

What 2 prosthetic groups are used at complex 1?

A

FAD.

FMN.

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13
Q

What gets oxidised at complex 1?

A

NADH.

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14
Q

What happens at complex 1 in the ETC?

A

NADH is oxidised and the electrons passed on to co-enzyme Q.

2 H+ ions are pumped into the inter-membranous space.

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15
Q

What prosthetic groups are used at complex 2?

A

None.

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16
Q

What happens at complex 2 in the ETC?

A

FADH2 is oxidised by co-enzyme Q.

The electrons 2 are also passed to complex 3 by co-enzyme Q to complex 3.

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17
Q

What gets oxidised at complex 2 in the ETC?

A

FADH2.

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18
Q

What oxidises FADH2 at complex 2?

A

Co enzyme Q.

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19
Q

Is succinate dehydrogenase involved in any other steps of aerobic respiration?

A

In the TCA cycle in step 6 where the 2 FADH2 molecules are made.

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20
Q

What happens at complex 3 in the ETC?

A

Co-enzyme Q delivers electrons from complex 1 and 2 to reduce complex 3.

2 more H+ ions are pumped into the inter-membranous space.

The electrons will then be handed to cytochrome C to be transferred to complex 4.

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21
Q

What prosthetic groups are used at complex 3?

A

Heme.

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22
Q

What happens at complex 4 in the ETC?

A

Cytochrome C delivers electrons to complex 4 and they are passed onto O2.

2 more H+ ions are pumped into the inter-membranous space.

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23
Q

What prosthetic groups does complex 4 have?

A

Heme.

Calcium ions.

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24
Q

What complexes will pump H+ into the inter membranous space?

A

Complexes 1, 3 and 4.

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25
Q

Which complexes contain iron sulphur proteins which are involved in the electron transfer process?

A

Complexes 1,2 and 3.

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26
Q

What is complex 1 called?

A

NADH dehydrogenase complex.

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27
Q

What is complex 2 called?

A

Succinate dehydrogenase.

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28
Q

What is complex 3 called?

A

Cytochrome reductase.

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29
Q

What is complex 4 called?

A

Cytochrome oxidase.

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30
Q

Why cant the H+ ions cross back through the inner mitochondrial membrane?

A

It is highly impermeable.

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31
Q

How can H+ ions re-enter the cell?

A

Through ATP synthase.

32
Q

ATP synthase is also known as what complex?

A

Complex 5.

33
Q

What happens when the H+ ions pass through ATP synthase?

A

It causes the enzyme to rotate which generates enough kinetic energy to phosphorylate an ADP.

34
Q

Is ATP a bi-functional enzyme?

A

Yes.

It allows the protons to pass through while generating ATP at the same time.

35
Q

At what steps of the TCA cycle is NADH formed?

A

Malate dehydrogenase step.

Alpha keto gluterate dehydrogenase step.

Isocitrate dehydrogenase step.

36
Q

Is any NADH formed at the PDH complex?

A

1.

37
Q

What are other sources of NADH?

A

Beta oxidation of fatty acids.

Sources from outside the mitochondria (glycolysis).

38
Q

What step in the TCA cycle is FADH2 generated?

A

Succinate dehydrogenase step.

39
Q

What are other sources of FADH2?

A

Glycerol phosphate shuttle.

Beta oxidation of fatty acids.

40
Q

How does the ATP formed in the ETC get to the cytoplasm?

A

Adenine nucleotide translocase will transport ATP to the cytoplasm.

41
Q

How does ADP get from the cytoplasm to the mitochondria?

A

Adenine nucleotide translocase will transport ADP from to the mitochondria to be phosphorylated.

42
Q

What 2 toxins can inhibit the transport of ATP from the mitochondrial matrix to the cytoplasm

A

Atractyloside.

Bongkrekic acid.

43
Q

What is adenine nucleotide translocase inhibited by?

A

Atractyloside.

Bongkrekic acid.

44
Q

What 3 inhibitors will affect complex 1?

A

Rotenone.

Piericidin A (antibiotic).

The barbiturate amytal.

45
Q

What inhibitor will affect complex 3?

A

Antimycin A (antibiotic).

46
Q

What 3 inhibitors will affect complex 4?

A

Carbon monoxide (CO).

Hydrogen sulphide (H2S).

Cyanide.

47
Q

What inhibitor will affect complex ATP synthase?

A

Oligomycin (antibiotic).

48
Q

Inhibitors of the ETC will result in what?

A

A decrease in ATP synthesis.

A decrease the rate of the ETC.

A decrease in oxygen consumption.

49
Q

What are uncouplers?

A

A class of inhibitors and they will create holes in the inner mitochondrial membrane.

50
Q

What effect will uncouplers have on the ETC?

A

The holes allow hydrogen ions to re-enter the mitochondrial matrix.

No proton gradient is formed.

Hydrogen ions do not pass through ATP synthase, so no ATP is generated.

51
Q

What are the 4 classes of uncouplers?

A

DNP (Dinitrophenol).

ASA (aspirin).

Thermogenin.

Ionophores.

52
Q

How will uncouplers affect ATP synthesis and oxygen consumption?

A

They will decrease ATP synthesis.

Increase the rate of the ETC.

Increase oxygen consumption

53
Q

The NADH and FADH2 produced in the ETC and PDH complex will be located in what organelle?

A

The mitochondrial matrix.

54
Q

Where are the 2 NADH molecules that are produced in glycolysis located?

A

In the cytoplasm

55
Q

What must happen to the 2 NADH molecules from glycolysis for them to enter the ETC?

A

They must travel from the cytoplasm to the mitochondrial matrix.

56
Q

What are the 2 shuttles that transport the NADH from glycolysis to the mitochondrial matrix?

A

The glycerol phosphate shuttle.

The malate-aspartate shuttle.

57
Q

How does the malate aspartate shuttle work?

A

NADH goes to the inter membranous space in the mitochondria.

An enzyme will transfer the electrons from NADH to reduce oxaloacetate and form malate and NAD+.

Malate crosses into the matrix where it is oxidised back to oxaloacetate.

This reduction allows NAD+ to be oxidised to NADH.

58
Q

What enzyme converts NADH and oxaloacetate to malate in the malate aspartate shuttle?

A

Cytosolic malate dehydrogenase.

59
Q

Can NADH cross the inner mitochondrial membrane?

A

No.

60
Q

What is NADH converted to to cross the mitochondrial membrane in the malate aspartate shuttle?

A

Oxaloacetate is reduced to malate.

61
Q

What enzyme converts malate to oxaloacetate and NADH in the malate aspartate shuttle?

A

Mitochondrial malate dehydrogenase.

62
Q

What happens in the glycerol phosphate shuttle?

A

NADH goes to the inter membranous space.

DHAP is oxidised to glycerol 3-phosphate.

NADH is reduced to NAD+.

G 3-P can enter the matrix and is re-oxidised to DHAP andFAD is reduced to FADH2.

63
Q

Will more energy be produced by use of the glycerol phosphate shuttle or by the malate aspartate shuttle?

A

The malate aspartate shuttle.

64
Q

What enzyme converts NADH and DHAP to glycerol 3-phosphate in the glycerol phosphate shuttle?

A

Cytosolic glycerophosphate dehydrogenase.

65
Q

What enzyme converts G 3-P to DHAP and FADH2 in the glycerol phosphate shuttle?

A

Mitochondrial glycerophosphate dehydrogenase.

66
Q

Every NADH that enters the glycerol phosphate shuttle will form what?

A

FADH2.

67
Q

How much ATP from NADH is generated from glycolysis if the malate aspartate shuttle is used?

A

6 ATP generated.

68
Q

How much ATP from NADH is generated from glycolysis if the glycerol phosphate shuttle is used?

A

4 ATP generated.

69
Q

How much total ATP is generated from glycolysis if the malate aspartate shuttle is used?

A

6 ATP from 2 NADH + 2 ATP from glycolysis = 8 ATP.

70
Q

How much total ATP is generated from glycolysis if the malate aspartate shuttle is used?

A

4 ATP from 2 FADH2 + 2 ATP from glycolysis = 6 ATP.

71
Q

The ETC is driven by the ratios of what molecules?

A

NADH/NAD+ and ATP/ADP.

72
Q

What molecules will activate the ETC?

A

A lot of NADH.

A lot of ADP.

73
Q

What are the substrates in the ETC?

A

NADH.

ADP.

74
Q

What are the products of the ETC?

A

NAD+.

ATP.

75
Q

What will inhibit the ETC?

A

High levels of NAD+.

High levels of ATP.

76
Q

What is hypoxia?

A

A deficiency in oxygen.

77
Q

What happens in the ETC if someone is hypoxic?

A

The energy from FADH2 and NADH will not be converted to ATP.

Biochem Take 2. (24 decks)

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