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POM 2 Cell biology > 2.6 Cell Integrity > Flashcards

2.6 Cell Integrity Flashcards

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1
Q

Generation of ATP and ATP equivalents through the use of kinases is known as what?

A

Substrate level phorphorlyation

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2
Q

What is it called when the electron transport chain reduces oxygen to water, coupling proton pumping to ATP production via ATP synthase?

A

Oxidative phosphorylation

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3
Q

Where do the reactions of oxidative phosphorylation occur?

A

In the inner membrane which folds and creates inward projections called cristae

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4
Q

What is the ΔG of the reoxidation of NADH?

A

-223 kJ/mol

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5
Q

What is the ΔG for the reoxdidation of FADH2?

A

-170 kJ/mol

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6
Q

What is the ΔG for ATP hydrolysis?

A

-31kJ/mol

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7
Q

In terms of energy, how does the oxidation of NADH and FADH2 lead to several ATP being produced?

A

The energy released from the re-oxidation of NADH and FADH2 (-223 and -170 kJ/mol) is enough to generate several phosphoanhydride bonds

As ATP hydrolysis releases -31 kJ/mol

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8
Q

What is the name of complex I membrane protein?

A

NADH dehydrogenase

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9
Q

What is the name of complex II membrane protein?

A

Succinate dehydrogenase

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10
Q

What is the name of membrane protein complex III?

A

Q-cytochrome C oxidoreductase

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11
Q

What is the name of Membrane protein complex IV?

A

Cytochrome c oxidase

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12
Q

What are the names of the two mobile carriers in the inner membrane of the mitochondria?

A

Co-enzyme Q (ubiquinone) and Cytochrome C

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13
Q

Which static membrane proteins can pump hydrogen ions into the inter-membrane space?

A

Complex 1, 3 and 4

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14
Q

Which complex does NADH pass its electron to?

A

Complex I NADH dehydrogenase

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15
Q

Which complex does FADH pass its electrons to?

A

Complex II succinate dehydrogenase

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16
Q

What happens when the membrane proteins accept electrons?

A

They can pump protons from the matrix into the intermmebrane space

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17
Q

Why does the deoxidation of FADH produce less ATP than NADH?

A

FADH passes its electrons directly to complex 2 (complex 1 is bypassed), meaning less H+ ions are pumped across

Since it is the flow of H+ ions which generates ATP, less H+ means less ATP

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18
Q

What are redox reactions?

A

Electron transfer reactions involving a reduced substrate (which donates electrons and therefore becomes oxidised) and an oxidised substrate (or oxidant) which accepts electrons and becomes reduced in the process

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19
Q

What is the redox potential?

A

The ability of a redox couple to accept or donate electrons

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20
Q

What does a negative redox potential indicate?

A

A high reducing power - this means the redox couple has a tendency to donate electrons to be gained by other substances, therefore reducing them

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21
Q

What does a positive redox potential indicate?

A

The redox couple has higher oxidising power than hydrogen, and therefore has a tendency to accept electrons, as it makes other things become oxidised (as they lose electrons

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22
Q

What happens as electrons as passed from one complex to another down the chain?

A

The electrons lose energy - meaning this transfer is energetically favourable

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23
Q

What happens to coenzyme Q when electrons are passed from FADH2 to it?

A

Q becomes reduced to QH2

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24
Q

What is ATP synthase?

A

A multimeric enzyme which consist of a membrane bound part F0 and an F1 part which projects into the matrix space

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25
Q

What does the direction of protein flow in ATP synthase dictate?

A

Whether it is ATP synthesis or hydrolysis

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26
Q

What happens to the energy which is stored in the electrochemical gradient of protons?

A

It is converted into mechanical rotational energy to drive the ATP synthase molecule around

27
Q

What happens as ATP synthase rotates?

A

The affinities for ATP and ADP change

Conformational energy flows from the catalytic subunit into bound ADP and Pi to convert it into ATP

28
Q

What happens when the concentration of H+ ions is higher in the matrix than in the intermembrane space?

A

ATP synthase will work in the other direction

ATP is hydrolysed to ADP and Pi

29
Q

What is the function of the F0 unit in ATPsynthase?

A

Rotates, coverting mechanical energy into kinetic energy

30
Q

What is the function of the F1 subunit of ATP synthase?

A

Synthesises ATP from ADP and Pi

31
Q

What is the current across the oxygen electrode proportional to?

A

The oxygen concentration in the sample chamber

32
Q

What happens when ADP is added to the sample of prepared mitochondria?

A

There is a rapid consumption of oxygen as the ADP is used up for oxidative phosphorylation

33
Q

Why is the current that arises from the oxygen electrode proportional to the oxygen concentration in the sample chamber?

A

The oxygen diffuses through the teflon membrane and is reduced to water at the platinum cathode

Therefore the more that is reduced, the greater the current

34
Q

What is uptake of O2 controlled by in the mitochondria?

A

Inorganic phosphate and ADP

35
Q

What is respiratory control?

A

Uptake of oxygen by mitochondria is controlled by the components of ATP production: Inorganic phosphate (Pi), and ADP.

36
Q

What is meant by a metabolic poison?

A

A molecule which interferes with the flow of electrons along the ETC or the flow of protons through ATP synthase

37
Q

How does Cyanide (CN-) and Azide work as a metabolic poison?

A

Bind with high affinity to the ferric (Fe3+) form of the haem group in the cytochrome oxidase complex blocking the final step of the ETC

38
Q

What step of the electron transport chain does Cyanide and Azide interfere with?

A

The final step as the electrons cannot be passed onto the cytochrome oxidase complex

39
Q

How does malonate work as a metabolic poison?

A

Closely resembles succinate and acts as a competitive inhibitor of succinate dehydrogenase - slows down the flow of electrons from succinate dehydrogenase to ubiquinone

40
Q

How does rotenone work as a metabolic poison?

A

It inhibits the transfer of electrons from complex I to ubiquinone

41
Q

How does oligomycin work as a metabolic poison?

A

Inhibits oxidative phosphorylation by binding to the ‘stalk’ of ATP synthase and blocking the flow of protons through the enzyme

42
Q

How does dinitrophenol work as a metabolic poison?

A

It can shuttle protons across the inner mitochondrial membrane, bypassing ATP synthase and uncoupling oxphos from ATP production

This increases metabolic rate and body temperature

43
Q

Why does the respiratory rate and body temperature increase when DNP causes bypass of ATP synthase?

A

The energy to pump H+ is dissipated as heat instead of forming ATP

44
Q

Which metabolic poison effects Complex I?

A

Rotenone

45
Q

Which metabolic poison works on Complex 4?

A

CN- and Azide ions

46
Q

Which metabolic poison works on ATP synthase?

A

Oligomycin

47
Q

How can DNP induce weight loss?

A

Transporting H+ ions across the membrane

Uncoupling oxidative phosphorylation from ATP production and therefore increasing metabolic rate

The body uses more fuel to pump H+ ions to restore the electrochemical gradient, leading to weight loss

48
Q

Why are fewer ATP molecules produced when FADH2 is reoxidised by the electron transport chain compared with NADH?

A

Complex I is bypassed and fewer protons are pumped to the intermembrane space

49
Q

The metabolic poison rotenone inhibits the oxygen consumption of mitochondrial suspensions metabolising citrate. However, it has little effect upon the oxygen consumption of a suspension of mitochondria metabolising succinate - why?

A

Rotonone does not inhibit complex II of the electron transport chain

50
Q

Why does glucose have no effect on the Oxygen concentration in the oxygen electrode experiment?

A

Metabolism of glucose occurs in the cytoplasm - this means the enzymes needed to break it down are in the cytoplasm not the matrix

51
Q

What affect does adding citrate have on the Oxygen Consumption during the oxygen electrode experiment?

A

Citrate is part of the TCA cycle - this means NADH and FADH can be produced

This coupled with proton pumping makes ATP so oxygen is CONSUMED

52
Q

What happens when DNP is added to the sample in the oxygen electrode?

A

Separates electron transport chain from oxidative phosphorylation

H+ ions can still flow and combine with oxygen to make water, so CONSUMPTION INCREASES

53
Q

Why does adding rotenone slow but not halt oxygen consumption?

A

When you still have succinate which donates to Complex II, so some oxygen is still consumed as rotenone only blocks complex I

54
Q

Why does the addition of cyanide to the oxygen electrode cease the electron chain?

A

It blocks the flow of H+ ions through ATP synthase, meaning the entirety of the electron transport chain is backed up

55
Q

What is the half equation representing the production of oxygen from hydrogen and oxygen?

A

2H+ + 1/2 O2 —-> H2O

56
Q

What is oxygen considered in the electron transport chain?

A

The final electron acceptor

57
Q

How can we use the Oxygen Electrode to measure changes in ETC?

A

By placing suspension of mitochondria into chamber, we can see effects of various substrates and inhibitors on ETC through changes in [O2]

58
Q

Why did people taking DNP die?

A

The margin between a helpful and fatal dose was very small

59
Q

How does substrate level phosphorylation differ from oxidative phosphorylation?

A

Oxidative phosphorylation utilises the electron transport chain

60
Q

How does NADH and FADH2 get into the mitochondrial matrix?

A

They use the malate and aspartate shuttle, as well as the glycerol phosphate shuttle

61
Q

What is the order of how the electrons are passed on in the electron transport chain?

A

Complex 1: NADH Dehydrogenase and Complex 2: Succinate dehydrogenase

Both pass to Q - Ubiquinone

Complex 3: Q-Cytochrome c oxidoreductase

Cytochrome c

Complex 4: Cytochrome oxidase

62
Q

Describe how malonate works as it has a similar chemical structure to succinate?

A
  1. It has a similar chemical structure to succinate
  2. This means it binds to succinate dehydrogenase instead of succinate
  3. Therefore, succinate deydrogenase cannot convert succinate into fumerate and hence less FADH2 is produced
  4. Hence the flow of electrons from FADH2 to Q is slowed
63
Q

Explain uncoupling in non-shivering thermogenesis?

A

UCP-1 a.k.a. thermogenin, is activated in response to a drop in core body temperature.

Like DNP it allows protons to bypass ATP synthase thereby releasing heat from the dissipation of the proton gradient.

POM 2 Cell biology (15 decks)

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