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Biochem midterm 2 > ETC and Oxidative Phosphorylation > Flashcards

ETC and Oxidative Phosphorylation Flashcards

1
Q

What generates the energy in the proton gradient?

A

Transferring electrons from NADH and FADH2 to oxygen

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2
Q

What is the free energy from the proton gradient used for?

A

Oxidative phosphorylation

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3
Q

Which complex in the ETC does the oxidation step occur?

A

In complex IV

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4
Q

In which complex does the phosphorylation of ADP to ATP occur?

A

In complex V

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5
Q

Do electrons get transferred in Complex V?

A

No its where ATP is synthesized

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6
Q

What is the final electron acceptor?

A

Oxygen is the final acceptor, it is reduced to H2O

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7
Q

What is the electron transfer potential?

A

It is what keeps the electrons flowing in forward direction

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8
Q

What is the flow of the 2 electrons through complex I

A

NADH2 - FMN (FMNH2) - Fe-S x3 - Q (QH2)

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9
Q

How many protons get pumped as a result of electron flow through complex I

A

4 protons get pumped

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10
Q

What are the oxidized and reduced versions of flavin mononucleotide?

A

FMN and FMNH2

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11
Q

What are the 3 states that Q can exist in?

A

Oxidized state - Q ; semiquinon -QH ; fully reduced - QH2

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12
Q

What is the final result of the 6 protons in complex I?

A

2 reduce Q to QH2 and 4 get pumped out into intermembrane space

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13
Q

From complex I, QH2 goes where?

A

Straight to complex III

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14
Q

Where does FADH2 carry its electrons to?

A

It goes straight to complex II

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15
Q

Do any protons get pumped when FADH2 reduces Q to QH2?

A

No, it isjust increasing QH2 content in the Q pool

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16
Q

The ETC is made up of a chain of electron carriers with _ redox potential

A

increasing

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17
Q

How many electrons can cytochrome c accept at a time?

A

One, eventhough QH2 has 2 to give.

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18
Q

What are the 3 types of hemes in complex III?

A

2 b-type: Heme bL and heme bH, 1 c-type Heme c1

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19
Q

What happens in first half of q cycle?

A

QH2 is oxidized, 1 electron goes to cytochrome c and one electron goes to reduce a Q into semiquinone state. 2 Protons pumped into intermembrans space

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20
Q

What happens in second half of q cycle?

A

Another QH2 is oxidized, 1 to cytochrome c and another to the semiquinone Q to fully reduce it to QH2. 2 more protons get pumped into intermembrane space

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21
Q

What is the net QH2 metabolism of the q cycle?

A

1, because one is generated

22
Q

What are the 4 electron accepting molecules in complex IV?

A

2 hemes - Heme a and Heme a3. 2 copper centers - copper a and copper b

23
Q

What is the flow of electron in complex IV?

A

From cytochrome c to copper a, then transfers to heme a then finally to heme a3/copper b site

24
Q

What site in complex IV reduces oxygen to H2O?

A

heme a3 / copper b site

25
Q

How do electrons flow to reduce molecular oxygen?

A

4 cytochromes c’s bring 4 electrons to make 2 molecules of H2O. The first 2 cleave the peroxide bridge and the next to protonate the OH groups on the Fe and Cu releasing the water

26
Q

What is the energy released from the reduction of water used to do?

A

Energy released from 2 reduced molecules of water causes 4 protons pumped into intermembrane space

27
Q

How many NADH or FADH2 is needed to release one water molecule?

A

2 to release water

28
Q

1 NADH contributes to how many protons being pumped?

A

10 - 4 in complex I, 0 in complex II, 4 in complex III, 2 in complex IV.

29
Q

1 FADH2 contributes to how man protons being pumped?

A

6 - 0 in complex I, 0 in complex II, 4 in complex III and 2 in Complex IV

30
Q

What does super oxide dismutase do?

A

It defends against reactive oxygen species. It can exist in an oxidized or reduced state.

31
Q

What does catalase do?

A

Catalyzes the reduction of hydrogren peroxide.

32
Q

What does the energy stuck in the intermembrane space do?

A

Drives ATP synthesis

33
Q

3 postulates for chemiosmotic theory

A
  1. Intact inner mitochondrial membrane, 2. e- transport through ETC creates proton gradien 3. ATP synthase catalyzes the phosphorylation of ADP driven by the movement of H+ across the inner membrane into the matrix
34
Q

What are the 2 components of proton motive force?

A

Chemical pH gradient and charge gradient

35
Q

What are the 2 assemblies of complex V?

A

Complex V is made of F0 which sits in the membrane and F1 that protrudes into the mitochondrial matrix.

36
Q

What is the stoichiometry of the F1 subunit?

A

3-alpha 3-beta , gamma, delta, epsilon

37
Q

In complex V which subunit rotates and which subunit is stationary?

A

F0 rotates and F1 is stationary

38
Q

What is are the 3 beta subunit conformations?

A

L-loosely binds to ADP and Pi, Tight- catalyzed the formation ATP, O-open to release ATP and allow another ADP and Pi to enter

39
Q

How does the beta-subunit change conformation?

A

The rotation of the gamma subunit

40
Q

What part of the membrane is ATP synthases rotating structure located?

A

Inner mitochondrial membrane

41
Q

Which subunit in complex V contains the catalytic center that synthesizes ATP?

A

F1 subunit

42
Q

What are the two channels of the alpha subunit?

A

Cytoplasmic half-channel that leads to the intermembrane space and the matrix half channel that leads to the matrix.

43
Q

How do protons enter complex V?

A

Through the two half channels in the alpha subunit.

44
Q

What is the environment inside the alpha subunit half-channels?

A

Hydrophilic aqueous environment

45
Q

What are the two environments that the c subunit interacts with?

A

Hydorphilic half channels and hydrophobic membrane

46
Q

What causes the rotation of the c subunits?

A

The transfer of protons down from intermembrane space and into the mitochondrial matrix

47
Q

How does the rotation of the c subunits drive ATP synthesis?

A

Rotation of the c subunits rotates the attached gamma subunit and changes the conformation of the beta subunits

48
Q

1 full rotation of the c subunits makes how many ATP?

A

3 ATP

49
Q

How do you get ADP into the matrix and ATP out of the matrix?

A

ATP-ADP translocase protein, this protein makes up about 15% of the inner mitochondrial membrane

50
Q

How do you regenerate the membrane potential after pumping out the extra negative charge with ATP?

A

Pump an extra proton

51
Q

How does NADH in the cytoplasm get oxidized if it cant pass through the inner membrane?

A

It passes its electrons to G3P shuttle and the shuttle passes the electrons to FADH2

52
Q

NADH from the cytoplasm contributes to how many protons getting pumped?

A

Protons from NADH in the cytoplasm go to FADH2 and enter ETC

Biochem midterm 2 (6 decks)

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