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BMS1011 > Oxidative phosphorylayion (ETC) > Flashcards

Oxidative phosphorylayion (ETC) Flashcards

1
Q

What do reduction potentials measure?

A

Affinity for electron acceptor and donors in Volts.
Free energy exchange in REDOX reactions is proportional to the ability of reactants to donate or accept electrons -delta G is represented by the redox potential

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2
Q

What is a central feature of metabolism?

A

Transfer of inorganic phosphate groups

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3
Q

What is responsible for the work done?

A

The flow of electrons in oxidation and reduction

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4
Q

What are the 4 ways electrons can be transferred in REDOX reactions

A
  1. Directly as electrons
  2. As H atoms (one H atom contains one proton and one electron)
  3. Transfer of a hydride ion (H-) (in reaction 6 of glycolysis to NAD+- oxidation and phosphorylation)
  4. Direct combination with oxygen
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5
Q

What does a highly negative redox potential indicate?

A

High electron transfer potential- ability to donate electrons will be stronger by NADH

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6
Q

What are the small activation energies overcome by in stepwise oxidation of sugar?

A

Body temperature

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7
Q

What does a highly positive redox potential indicate?

A

Oxygen will be a good electron acceptor

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8
Q

How many carriers are in the ETC?

A

5

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9
Q

What are the metabolic carriers?

A

NAD+ and FAD

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10
Q

What are the ETC carrier components?

A

Ubiquinone, Cytochromes and Fe-S proteins

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11
Q

Where does ubiquinone (Q complex) move in the membrane?

A

It can move freely in the hydrophobic part of the membrane. It transfers the electrons from complext I and II to complex III (in reduced form of QH2)

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12
Q

What is Q called?

A

Ubiquinone

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13
Q

What is QH2 called?

A

Ubiquinol

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14
Q

What is a cytochrome?

A

Heme containing proteins

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15
Q

What are the mobile carriers in ETC?

A

QH2 and cytochrome C

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16
Q

What does complex I do?

A

NADH dehydrogenase; catalyses electron transfer from NADH to ubiquinone Q to form ubiquinol (QH2) where it transfers electrons to complex III

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17
Q

What does complex II do?

A

Succinate dehydrogenase; Contains CA intermediate succinate and cataylses electron transfer from succinate (formation of FADH as in CAC) to QH2 ubiquinone (which transfers electrons to complex III)

18
Q

What does complex III do?

A

Ubiquinone: cytochrome c oxidoreductase

  • contains cytochromes and Fe-S centres
  • receives electrons from ubiquinol (QH2) and reoxidises to ubiquinone, Q. (very complex)
  • 4 H pumped across (2 from matrix, 2 from QH2)
19
Q

What does complex IV do?

A 
Cytochrome oxidase; catalyses e- transfer to O2
- contains cyt a,a3 and 2 Cu ions 
- Involves 2 e- centres to reduce O2
O2+ 4H+ 4e-  --> 2H2O 
- 2 H+pumped across
  • transfers electrons DIRECTLY to oxygen
20
Q

How is a proton gradient formed?

A

From the transfer of electrons down electron transport chain

21
Q

What is the proton gradient affected by?

A

The pH gradient (matrix pH= 8 and outside pH=7)

- Voltage gradient (matrix is electronegative compared to outside space)

22
Q

To try and make the membrane more neutral, what happens?

A

A proton motive force occurs where the protons flow in from intermembrane space to matrix. (PMF)

23
Q

When E0 is sufficiently large, what occurs in ETC?

A

PROTONS are pumped across the inner mitochondrial membrane to INTERMEMBRANE SPACE

24
Q

Which strucutre controls flow of protons back into the matrix?

A

ATP synthase

25
Q

How is ATP actually snythesised in ETC?

A

From the ADP and Pi using the energy obtained from the protomotive force (PMF) - ATP synthase being an enzyme links enzymatic reactions with electron transport

26
Q

What is chemiosmotic theory?

A

Energy derived from electron transfer reactions is temporarily stored as transmembrane differnce in charge and pH which subsequently drives the formation of ATP in oxidative phosphorylation

27
Q

What maintains the proton gradient?

A

the complexes in the ETC pumping protons into intermembrane space

28
Q

What would happen if the ATP synthase stopped turning?

A

Cell would die because no electric potential left to generate energy

29
Q

Which side of the inner membrane has a highly positive charge of protons; intermembranal space or matrix?

A

The intermembranal space. Protons are pumped in ETC from matrix TO INTERMEMBRANAL SPACE to maintain the concnetration gradient.

30
Q

What does oxidative phosphorylation mean?

A

That the transfer of electrons causes oxygen to be reduced to H2O as well as phosphorylation of ADP to ATP.
(Synthesis of ATP and transfer of e-s are COUPLED)

31
Q

What is the F0 component of ATP snythase?

A

The channel part; protons enter from the intermembrane space (proton conc high)

32
Q

What is the F1 component of ATP synthase?

A

Movement of electrons causes conformational change which activates enzymatic activity (rotates once H atom bind to it)
- Also converts ADP to ATP

33
Q

What is oxidative phosphorylation regulated by?

A

Level of ADP in the system

34
Q

What needs to occur to maintain coupling?

A

The mitochondiral membrane (inner must remain intact)

35
Q

What is an artificial situation to break the inner mitochondrial membrane and what is the effect?

A

When you harvest mitochondria in lab can cause mechanical damage (inner membrane). Membrane becomes leaky- can’t maintain and generate PMF so cant synthesise ATP (no more proton gradient)

  • electron transfer occurs but no phosphorylation (processes have been uncoupled)
36
Q

What are chemicals that can cause uncoupling?

A

2,4-dinitrophenol (DNP) can bind protons in intermembranal space and diffuse through through innner mitochondiral membrane back into matrix (destroys proton gradient so no PMF) - oxygen consumption occuring but no ATP synthesis hence uncpoupling

37
Q

What do venturicidin and oligomycin do?

A

Inhibit ATP synthase complex (block F0 channel and prevent movement of protons back into mitochondrial matrix)-uncoupled processes -no ATP synthesis - inhibit electron transport and ATP synthesis only in coupled mitochondira

38
Q

What is a natural uncoupler?

A

Brown (due to mitochondria) fat in babies. Mitochondria have uncoupling protein called thermogenin (because babies need to keep warm rather than produce energy) - transfer electrons like usual but energy produced for synthesising ATP is instead used to generate heat. (does’t move through ATP synthase)

  • Hibernating animals
39
Q

Which complex does cyanide (CN-) inhibit?

A

It inhibits at complex IV -prevents transfer of electrons to oxygen

40
Q

What do the inhibitor inhibit?

A

BOTH the electron transport AND the ATP synthesis

41
Q

What does an increase in ADP activate?

A

ATP synthase,electron transfer, and oxygen consumption (regulation is respiratory control)

BMS1011 (5 decks)

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