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Metabolism > Oxidative phosphorylation > Flashcards

Oxidative phosphorylation Flashcards

1
Q

What are the relative concentrations of ATP, AMP ADP?

A

ATP- high: 6mM
ADP - low: 10micromoles
AMP - low: 5 nm

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2
Q

What is a reaction that adenylate cyclase catalyses

A

2ADP –> ATP + AMP

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3
Q

What two signals increase ATP production?

A

Rising ADP

Rising AMP

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4
Q

How does rising AMP signal more ATP production?

A

Cytoplasmic signal to activate glycolysis via AMP activated PFK enzyme stimulates ATP generation

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5
Q

How does rising ADP signal more ATP production?

A

Signal to mitochondria so controls ATP synthesis at mitochondrial level

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6
Q

What is the difference between the mitochondrial inner and outer membranes?

A

Outer is permeable due to large porin channels

Inner is highly impermeable with specific transporters

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7
Q

What proportion of ATP is from oxidative phosphorylation?

A

95%

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8
Q

Sum up oxidative phosphorylation

A

Indirect coupling of energy release from oxidation of energy substrates to ATP synthesis: through transfer of electrons from NADH and FADH2 to oxygen by electron carriers.

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9
Q

How do red blood cells make ATP?

A

Substrate level phosphorylation

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10
Q

Where are hydrogen carriers located?

A

Mainly in the mitochondria

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11
Q

What are the 2 steps of oxidative phosphorylation?

A

Electron transport and thus Generation of proton gradient

ATP synthesis

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12
Q

What happens after all hydrogen carriers oxidised?

A

Transport electrons to Oxygen via ETC
Produces water
Generate proton gradient across inner mitochondrial membrane

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13
Q

What does proton gradient couple?

A

Electron transfer to ATP synthesis

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14
Q

What does chemiosmotic therory state?

A

Electrons moving down respiratory chain drives proton pumping from mitochondria matrix to IM space

IMM impermeable to protons

Creates electrical and pH gradient across IMM

Protons move down gradient into matrix via F0F1 ATP synthase driving ATP synthesis

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15
Q

What does 2-4DNP do?

A

Uncouples substrate oxidation and ATP generation.

Collapses Proton motive force by carrying protons across IMM and dissipating gradient
inhibit ATP formation

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16
Q

Describe solubility of 2-4DNP, why is this relevant?

A

Lipophilic, so carries proton across IMM

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17
Q

What stops and what continues after you apply 2-4 DNP?

A

Electron transport and O2 consumption continues

Phosphorylation stops

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18
Q

What is the most important factor for controlling electron flow?

A

ADP availability

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19
Q

How does ADP exercise respiratory control?

A

Discharge of proton gradient regulates ETC and thus substrate oxidation

BUT electrons can’t flow through ETC unless ADP is available for simultaneously phosphorylation to ATP

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20
Q

How many complexes make up the electron transport chain?

A

4

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21
Q

What does complex 1 do?

A

Uses NADH as substrate, electrons reduce FMN to FMNH2.

Electrons move to Fe-S, then to ubiquinone (Q), forming QH2

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22
Q

How many protons are pumped at complex 1?

A

4

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23
Q

Which complex doesn’t span membrane?

A

Complex 2

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24
Q

What is complex 2 physically linked to?

A

Succinate dehydrogenase from TCA, linked to FADH2

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25
Q

What does complex 2 do?

A

FADH2 as its substrate

Two electrons pass from FADH2 to Fe-S clusters and electrons are passed to Q.

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26
Q

Does any proton pumping occur at complex 2?

A

No, it doesnt fully span the membrane

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27
Q

What does complex 3 do?

A

Uses Q as its substrate and accepts 2e-.

Electrons to cytochrome C.

Complex III stores an electron - Q cycle.

The other electron passes to an Fe-S called the Rieske protein which then transfers it to cytochrome C.

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28
Q

What does complex 4 do?

A

Uses cytochrome c and oxygen as its substrate to generate H2O (oxygen is terminal electron acceptor). Cu and haem complex carries electrons.

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29
Q

How many protons does complex 3 pump?

A

4

30
Q

How many protons does complex 4 pump (per cytochrome C and per O2)?

A

Per cyt C: 2

Per O2: 4

31
Q

How many H+ extuded for each FADH2 and NADH oxidised?

A

NADH: 10H+
FADH: 6H+

32
Q

Describe how two molecules of water are formed?

A

Four electrons are removed from four molecules of cytochrome c and transferred to O2, producing 2 x H20.

Eight protons are removed from the mitochondrial matrix (only four are translocated across the membrane).

33
Q

What are complexes linked by?

A

Small mobile electron carriers

1) Ubiquinone (Q)
2) Cytochrome C

34
Q

What property of ubiquinone affects where it is found?

A

Long hydrocarbon tail so hydrophobic, retained within inner membrane

35
Q

What does cytochrome C contain?

A

Haem prosthetic group

36
Q

What is the property of cytochrome C, how does this affect location?

A

Water soluble so resides at periphery of membrane closer to IMS

37
Q

What do reaction centres of large protein complexes contain?

A

Transition metals at reaction centre (for redox)

38
Q

What are the different sorts of transition metals found in reaction centres? (in increasing affinity for electrons)

A

Iron in iron sulphur clusters
Iron as haem
Copper

39
Q

What metal(s) does each complex contain?

A 
I: Fe-S
II: Fe-S
III: Fe-S
Cytochrome C: Haem
IV: Haem and Cu
40
Q

What are the reactions involving iron and copper that allow electron transfer?

A

Fe2+ Fe3+ + e-

Cu+ Cu2+ + e-

41
Q

What is the benefit of different complexes have different oxidation/reduction centres?

A

Allow sequential oxidation/reduction reactions with increased redox potential which drags electron through oxidation/reduction reactions along ETC

42
Q

Along ETC, sequential oxidation/reduction with increased…

A

Redox potential

43
Q

What is the ultimate/terminal electron acceptor?

A

Oxygen

44
Q

How does NADH cross IMM?

A

Malate/aspartate shuttle (IMM impermeable to NADH)

45
Q

How does the malate/aspartate shuttle work?

A

NADH is required for converting oxaloacetate to malate on the outside, and produced when converting malate to oxaloacetate on the inside.

Malate can enter the matrix and Aspartate can leave matrix, fuelling compartmentalised reactions

46
Q

What is used to enhance electron entry into ETC when cytoplasmic NADH low?

A

Glycerol 3 phosphate

47
Q

What occurs in the glycerol phosphate shuttle?

A

Cytoplasmic NADH is converted to FADH2 in the inner-mitochondrial membrane and electrons are passed directly to QH2.

48
Q

Why is yield lower for glycerol phosphate shuttle?

A

The yield is lower because FAD rather than NAD+ is the electron acceptor, the use of

49
Q

What is the importance of the glycerol phosphate shuttle?

A

The use of FAD enables electrons from cytoplasmic NADH to be transported into the mitochondria against an NADH concentration gradient.

50
Q

Compare the movement of NADH and FADH2

A

NADH: diffusible in matrix
FADH2: enzyme bound in mitochondrion

51
Q

Describe the basic structure of ATP synthase

A

F0 subunit: integral membrane protein forms proton channel

F1: Complex (alpha, beta, gamma, delta, epsilon) with 3 catalytic sites for ATP synthesis

52
Q

Describe relationship between 2 subunits of ATP synthase

A

Functionally linked so protons only flow when ATP being synthesised (dependent on ADP conc as respiratory control)

53
Q

What is the mechanism of ATP synthesis via ATP synthase?

A

Protons enter F0 subunit inducing rotation of gamma subunit of F0 linked to F1

Changes environment of 3 beta subunits of F1 drives conformational change of beta subunits of F1
Propels each binding site through different conformational states and drives phosphorlylation of ADP

54
Q

What are the different states of beta subunit, what happens in each one?

A

Open subunit: ATP can leave, ADP and Pi enter
Loose: ADP and Pi held in place
Tight: ATP resynthesised

55
Q

Describe the relationship between the 3 beta subunits

A

Each goes through open, loose tight resulting in 1 ATP synthesised. so 3 subunits work in cooperative fashion

56
Q

How many protons to make one ATP by ATP synthase?

A

3

57
Q

Where is ATP/ADP exchanger found?

A

IMM

58
Q

What drives ATP/ADP exchanger?

A

Membrane potential component of proton motive force as ATP is more negatively charged than ADP

59
Q

Where does ATP/ADP transporter transport ATP and ADP?

A

ATP to cytoplasm

ADP into matrix

60
Q

What are the charges of ATP and ADP?

A

4-

3-

61
Q

How is Pi moved into matrix for ATP synthesis?

A

H+/Pi co transporter in IMM

62
Q

What does H+ Pi cotransporter do?

A

Transport H2PO4- and H+ across IMM into matrix

63
Q

What protein exchangers are present in the IMM that rely on H+ graient?

A

ANT (adenosine nucleotide translocase)

H+/Pi cotransporter

64
Q

How does pyruvate enter matrix?

A

Pyruvate/H+ cotransporter in IMM

65
Q

How do transporters discharge the electrochemical gradient?

A

ATP/ADP: Makes inside of mitochondria (matrix) more positive

H+/Pi: Takes H+ away from ATP synthase

66
Q

What do mitochondria in response to rise in Ca2+ , why is this important?

A

Increase uptake which is electrogenicaly favourable due to PMF

Plays role in regulating TCA cycle

67
Q

Where does thermogenesis mainly occur?

A

Brown adipose tissue in newborns and hibernating animals

68
Q

How is Proton motive force dissipated in brown adipose tissue, what is the consequence?

A

Uncoupling protein 1 (thermogenin) expressed that dissipates H+ gradient/PMF without making ATP - energy released as heat

69
Q

What does uncoupling protein 1 uncouple?

A

Oxidative phosphorylation and ETC so continue to oxidise fuel to generate proton gradient

70
Q

The electrochemical gradient across the inner mitochondrial membrane can be used for all of the following functions

A

ATP/ADP exchange
ATP synthesis
Calcium transport into the mitochondrion
Thermogenesis

71
Q

In the presence of an oxidisable substrate, the rate of oxygen consumption by tightly coupled isolated mitochondria will be increased by the addition of…

A

2,4-dinitrophenol

Metabolism (13 decks)

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