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POM > MBC - Cell integrity > Flashcards

MBC - Cell integrity Flashcards

1
Q

What is the difference between substrate-level and oxidative phosphorylation?

A

Substrate-level: direct generation of ATP/GTP by kinases

Oxidative: indirect bulk generation of ATP in mitochondria

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2
Q

How is oxidative phosphorylation increased in the inner membrane of mitochondria?

A

The cristae are folds which increase surface area for ETC proteins

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3
Q

What is complex I?

A

NADH-Q oxidoreductase/NADH dehydrogenase

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4
Q

What are the 4 membrane proteins in ETC?

A

Complex I - NADH-Q oxidoreductase/NADH dehydrogenase

Complex II - Succinate-Q reductase/ succinate dehydrogenase

Complex III - Q-cytochrome C oxidoreductase

Complex IV - cytochrome C oxidase

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5
Q

What is complex II?

A

Succinate-Q reductase / succinate dehydrogenase

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6
Q

What is complex III?

A

Q-cytochrome c oxidoreductase

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7
Q

What is complex IV?

A

cytochrome C oxidase

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8
Q

What are the 2 electron carriers in ETC?

A

Co-enzyme Q (ubiquinone)

Cytochrome C

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9
Q

Why does electron only go one way in the ETC?

A

Because complex IV has higher affinity for e- than complex I

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10
Q

How does Complex I acquire e- from NADH?

A

Complex I has a higher affinity for e- than NADH

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11
Q

How does proton go from matrix to intermembrane space?

A

Complex I, III, IV accept e- and by doing so releases energy to pump protons across membrane

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12
Q

Where is complex II from?

A

An enzyme from the TCA cycle (It sits in the inner mitochondrial membrane)

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13
Q

What does complex II do?

A

It uses FAD as cofactor to directly communicate w/ Coenzyme Q.

As e- pass from FADH2 to Coenzyme Q, Complex II picks up a pair of protons, regenerating FAD and forming QH2

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14
Q

When does ETC end?

A

When complex IV has 4e- to from H2O

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15
Q

Why are fewer ATP molecules produced when FADH2 is reoxidised by ETC compared with NADH?

A

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

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16
Q

What does cytochrome c do?

A

transfers electrons from complex III to complex IV

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17
Q

How do redox reactions govern oxidative phosphorylation?

A

By substrates’ ability to accept/donate e-

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18
Q

How to define redox reactions?

A

Electron transfer reaction involving a reduced & oxidised substrate

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19
Q

What does a reduced substrate do?

A

It donates e- and gets oxidised

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20
Q

What does an oxidised substrate do?

A

It accepts e- and gets reduced

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21
Q

What is a redox couple?

A

A substrate that can exist in both reduced and oxidised form

22
Q

What is the reduction/redox potential?

A

Ability for redox couple to accept/donate e-

23
Q

What is the standard redox potential measured against?

A

The hydrogen electrode

24
Q

What does a standard NEGATIVE redox potential indicate?

A

Tendency to donate e-, it has more reducing power than H

eg NAD+/NADH

25
Q

What does a standard POSITIVE redox potential indicate?

A

Tendency to accept e-, it has more oxidising power than H

eg Fe3+/2+ , 0.5O2/H2O

26
Q

How does e- energy progress along the chain?

A

Transfer of electron is energetically favourable, e- loses energy as it progresses along chain

27
Q

What is ATP synthase?

A

A multimeric enzyme that consist of a membrane bound part and a part that projects into the matrix

28
Q

How does ATP synthase work to synthesise ATP?

A

Rotation of central shaft influences conformation and arrangements of subunit, energy from conformation promote formation of ATP from bound ADP + Pi

29
Q

What are the steps to rotate the shaft of ATP synthase?

A
  1. H+ goes down proton gradient (IMS to matrix)
  2. Chemical energy stored in proton gradient is converted to mechanical/rotational energy
  3. H+ drive rotor by binding to rotor subunits (only protonated subunits can rotate into membrane)
30
Q

How does hydrolysis happen with ATP synthase?

A

When H+ gradient is higher in the matrix than the intermembrane space, ATP breaks down into ADP + Pi to provide energy to move H+ to IMS

31
Q

What is the oxygen electrode?

A

A device to measure O2 conc. in solution

32
Q

What is the base of the oxygen electrode chamber formed by?

A

Teflon membrane (permeable to O2)

33
Q

What is under the Teflon membrane?

A

Compartment with Pt cathode (+) & Ag anode (-)

34
Q

What happens when voltage is applied between electrodes?

A

O2 diffuses through membrane - reduced at Pt cathode

At Ag anode, Ag oxidised to AgCl by KCl electrolyte

35
Q

How can we use the oxygen electrode to test components of ETC?

A
  1. Prepare suspension of mitochondria + place it in

2. Observe oxygen consumption of suspension for a set time period to determine various substrates and inhibitors

36
Q

How do we conduct the test w/ oxygen electrode?

A
  1. Measure baseline respiration
  2. Add known amount of ADP (rapid consumption of O2 -steeper gradient)
  3. Calculate ratio of amount of ADP phosphorylated by mitochondria to amount of O2 consumed
37
Q

What is the ADP:oxygen index?

A

Measure of efficiency of mitochondrial phosphorylation system

38
Q

What happens when all the ADP has been consumed? (Oxygen electrode test)

A

Level of respiration returns to baseline gradient

39
Q

How long does each ATP molecule live for?

A

1-5 min(s)

40
Q

Around how many times is ATP recycled a day?

A

300 times

41
Q

What happens when oxidative phosphorylation/ATP synthesis is interrupted?

A

Cell death

42
Q

What is the most common failure to oxidative phosphorylation/ATP synthesis?

A

Lack of O2

(Hypoxia - diminished O2)

(Anoxia - total lack of O2)

43
Q

What is respiratory control?

A

Uptake of O2 by mitochondria which is controlled by ADP+Pi

Allows body to adapt O2 consumption to body energy requirements

44
Q

What are metabolic poisons?

A

Molecules that interfere w/ ATP synthesis

  • flow of e- along ETC
  • flow of H+ through ATP synthase
45
Q

What are some examples of metabolic poisons?

A

Cyanide (CN-) & Azide (N3-)

Malonate

Rotenone

Oligomycin

Dinitrophenol (DNP)

46
Q

What does Cyanide & Azide do?

A

Bind w/ high affinity to Fe3+ of haem group in complex IV

47
Q

What does malonate do?

A

competitively inhibit succinate dehydrogenase

(resembles succinate)

Slows down flow of e- from succinate to ubiquinone

48
Q

What does rotenone do?

A

Inhibits transfer of e- from complex I to ubiquinone

49
Q

what does oligomycin do?

A

Bind to stalks of ATP synthase, block flow of proton

Inhibiting oxidative phosphorylation

50
Q

What does dinitrophenol (DNP) do?

A

Shuttles protons across inner mitochondrial membrane

51
Q

Why is dinitrophenol dangerous?

A

It uncouples OxPhos from ATP production - increases metabolic rate & body temp

POM (22 decks)

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