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BIO1332 Biochemistry > Mitochondrial e- Transport & ATP Synthesis > Flashcards

Mitochondrial e- Transport & ATP Synthesis Flashcards

1
Q

Define oxidative phosphorylation.

A

The process in which ATP is formed as a result of transfer of e- from NADH/FADH2 to oxygen by a series of e- carriers.

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2
Q

Define the etc.

A

a specialised set of protein complexes & e- carriers.

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3
Q

Which is the only complex in the etc not to span the membrane (located on matric side only)?

A

Cytochrome c

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4
Q

Give the 2 highly mobile e- carriers that shuttle e-.

A

Q & cytochrome c.

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5
Q

Why do e- flow through the etc?

A

Each complex/carrier has a lower free energy than the preceding member, so e- flow spontaneously down the chain.

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6
Q

How do e- generate ATP?

A

e- motive force is converted into H+ motive force.

H+ motive force is converted into phosphoryl transfer potential.

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7
Q

Describe Complex I of the etc.

A

NADH-Q reductase
34 polypeptide chains
membrane spanning structure & long arm extending into matrix.

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8
Q

Give the prosthetic groups in Complex I of the etc.

A

flavin mononucleotide

iron-sulphur clusters

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9
Q

Describe the role of Complex I in the etc.

A

2e- transferred from NADH to FMN.
FMN reduced to FMNH2.
FMNH2 transfers 2e- to series of Fe-S clusters.
2e- transferred to coenzyme Q, reducing it to QH2.
4H+ are pumped from matrix during this process.

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10
Q

Describe Complex II of the etc.

A

Succinate Q-reductase
Bound to inner mitochondrial membrane
also takes part in citric acid cycle

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11
Q

Describe the role of Complex II in the etc.

A

FADH2 loses 2e- to coenzyme Q via Fe-S clusters.

does not pump H+ because less ATP from FADH” compared to NADH.

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12
Q

Describe Coenzyme of the etc.

A

Coenzyme Q.

ubiquinone

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13
Q

Why is Coenzyme Q known as a ubiquinone?

A

it is a ubiquitous quinone in all biological systems.

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14
Q

Describe the role of Coenzyme Q in the etc.

A

accepts 2e- from Complex I or II to become QH2 & transfer them to Complex III.
hydrophobic, rapidly diffuses within inner mit. membrane.

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15
Q

Describe the role of Complex III in the etc.

A 
Catalyses the transfer of 2e- from QH2
for each e- transferred from QH2, 2H+ pass out of matrix & 1 is donated to Q.
occurs twice (2e- from Complex I & II each) so overall 4H+ pumped from matrix.
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16
Q

Describe Complex III of the etc.

A

Q-cytochrome c oxidoreductase

homo-dimer with 11 distinct polypeptide chains.

17
Q

Give the prosthetic groups in Complex III.

A

heme

Fe3+ <> Fe2+

18
Q

Describe the 5th protein in the etc.

A

Cytochrome C.

small soluble protein with c-type heme

19
Q

Describe the role of the 5th protein in the etc.

A

carries 1e- from Complex III to Complex IV.

20
Q

Describe Complex IV of the etc.

A

Cytochrome c oxidase

13 polypeptide chains

21
Q

Give the prosthetic groups in Complex IV.

A 
-2 heme prosthetic groups 
Fe a^3+ & Fe a3^2+
-2 copper ions
Cu B^1+ & Cu A^2+
-these are redox centres
22
Q

Describe the role of Complex IV of the etc.

A

heme a3 & CuB is the site of reduction of oxygen > water

for every NADH that enters the chain, 2x cyt c transfer 2e- to oxygen.

23
Q

Why are 2 NADH/FADH2 required to split one molecule of oxygen?

A

because 4H+ & 4e- are required.

24
Q

How many of the complexes in the etc are proton pumps?

A

3 out of 5.

25
Q

Give how a proton gradient is created.

A

H+ are pumped from matrix to inner mit. membrane as e- flow through etc.

26
Q

Give Complex V of the etc.

A

ATP synthase

27
Q

How are oxidation & ATP synthesis coupled?

A

Transmembrane H+ movement.

28
Q

Describe the F1 catalytic subunit of ATP synthase.

A

extends into matrix
5 types of polypeptide chain: a3, B3, y, δ & ϵ
majority of head is a3 & B3 (also has δ)
stalk is y & ϵ

29
Q

How is ATP, made independently of the etc, released from ATP synthase?

A

the flow of H+ releases the ATP

30
Q

Overall, 1 NADH =

A

10H+ translocated = 2.5 ATP

31
Q

Overall, 1 FADH2 =

A

6 H+ translocated = 1.5 ATP

32
Q

Give the inhibitors of oxidative phosphorylation between Complex I & Q.

A

Rotenone (insecticide made by plants)

Amytal (barbiturate)

33
Q

Give the inhibitors of oxidative phosphorylation between Q & Complex 3.

A

Antimycin A (produced by Streptomyces).

34
Q

Give the inhibitors of cytochrome c oxidase.

A

Cyanide (binds Fe3+)

CO (binds Fe2+)

35
Q

What are uncoupling proteins?

A

disrupt the coupling of etc & ATP synthase by allowing protons to flow through the membrane without going through ATP synthase.

36
Q

Give examples of synthetic uncoupling proteins.

A

Lipophilic proton carriers

Aspirin in high conc.

37
Q

Give other uses of proton motive force.

A

drive the rotation of flagella basal body
active transport
e- potential
NADPH synthesis

BIO1332 Biochemistry (12 decks)

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