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COB Biochemistry > Lectures 28-29 Oxidative Phosphorylation > Flashcards

Lectures 28-29 Oxidative Phosphorylation Flashcards

1
Q

Which membrane of the mitochondria is permeable due to the presence of porin?

A

Outer membrane

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2
Q

Which membrane of the mitochondria is impermeable and relies on metabolite transporters?

A

Inner membrane

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3
Q

What component of the mitochondria is the site of TCA cycle and fatty acid oxidation?

A

Mitochondrial matrix

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4
Q

Where does oxidative phosphorylation take place?

A

Inner membrane of mitochondria

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5
Q

What are the 2 electron carriers involved in the electron transport chain?

A

Coenzyme Q/Ubiquinone, Cytochrome c

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6
Q

Coenzyme Q/Ubiquinone

A

Transfers electrons from Complexes I and II to Complex III (most common=COQ 10)

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7
Q

Cytochrome c

A

Shuttles electrons from Complex III to Complex IV; Final component which catalyzes reduction of O2 to H2O

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8
Q

What are the prosthetic groups for Complex I (NADH-Q oxidoreductase)?

A

FMN, Fe-S

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9
Q

What are the prosthetic groups for Complex II (Succinate-Q reductase)?

A

FAD, Fe-S

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10
Q

What are the prosthetic groups for Complex III (Q-cytochrome c oxidoreductase)?

A

Heme bH, bL, C1 and Fe-S

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11
Q

What are the prosthetic groups for Complex IV (cytochrome c oxidase)?

A

Heme a, a3, CUa and CUb

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12
Q

Name the oxidized form of coenzyme Q

A

Q, Ubiquinone

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13
Q

Name the reduced form of ocenzyme Q

A

QH2, Ubiquinol

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14
Q

Friedreich’s Ataxia

A

Mutation in Frataxin which helps synthesize Fe-S clusters; affects CNS/PNS/heart/skeletal system

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15
Q

Complex I of the ETC

A

First point of entry for electrons from NADH; L shaped with horizontal arm in inner membrane and vertical arm projecting into matrix; oxidizes NADH and reduces coQ; H+ moved to inner membrane from mito matrix

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16
Q

Complex II of the ETC

A

FADH2 enters here, does not leave complex; electrons from FADH2 are transferred to FeS and then to coQ to form QH2; DOES NOT PUMP PROTONS

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17
Q

Complex III of ETC

A

Passes QH2 electrons to cytochrome c; flow of electrons leads to transport of 2 protons to cytoplasmic side; QH2 is oxidized and Cyt c is reduced

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18
Q

Q cycle

A

Occurs in complex III; Passes one electron to cytochrome c, the other to a bound Q; Then another QH2 gives its electrons to a cytochrome c and the Q anion to form QH2

19
Q

Complex IV of ETC

A

Last complex; transfers electrons from reduced cytochrome c to molecular oxygen = the final electron acceptor!

20
Q

How many protons are transported by Complex IV?

A

4 pumped protons and 4 chemical protons

21
Q

Partial reduction of oxygen forms what?

A

Free radicals

22
Q

What are some pathological conditions that involve free-radical injury?

A

Parkinson’s disease, Ischemia; reperfusion injury

23
Q

How do antioxidants defend against free radicals?

A

SOD: allows free H+ to convert oxygen radicals into oxygen and peroxide; catalase: breaks down peroxide into oxygen and water

24
Q

Chemiosmotic hypothesis

A

The transport of protons from the matrix to cytoplasmic side of inner membrane generates a pH gradient and membrane potential which constitutes a protein motive force used to drive ATP synthesis
*Evidence: bacteriorhodopsin experiments

25
Q

ATP synthase

A

Ball and stick structure embedded in inner membrane; F0 = stick with proton channel; F1=ball protruding into matrix an containing catalytic domains

26
Q

What polypeptide chains of ATP synthase (F0 subunit) are catalytically active/constitute active site?

A

the beta subunits

27
Q

How are the F0 and F1 subunits of ATP synthase connected?

A
  1. central gamma/epsilon stalk

2. exterior column of 1 alpha, 2 beta, 1 delta subunit

28
Q

What is the function of ATP synthase?

A

Stabilizes molecules to rotational force during catalysis, maintains curvature of inner membrane

29
Q

What is the role of the proton gradient?

A

Release ATP from the synthase

30
Q

What is the function of the gamma subunit of ATP synthase?

A

Forms stalk, creates asymmetry in the structure, rotation causes the switch between L, T, O conformations

31
Q

What are the three steps in ATP synthesis?

A
  1. Binding of ADP and Pi (L conformation)
  2. ATP synthesis (T conformation)
  3. Release of ATP (O conformation)
32
Q

Proton conducting unit of ATP synthase

A

c subunit: 2 alpha helices that span membrane with aspartic acid in the middle; a subunit has cytoplasmic half-channel and matrix half-channel allowing proton to enter and pass partway (a subunit connects F0 and F1)

33
Q

What drives the rotation of the c ring in the F1 subunit of ATP synthase?

A

Proton motion (neutralizes aspartic acid in the cytoplasmic subunit and allows rotation of c ring moving aspartic acid and eventually H+ out)

34
Q

What powers each 360 degree rotation of the c ring and what does this rotation generate?

A

3 H+ power the rotation, which generates 3 ATP

35
Q

Role of ATP-ADP translocase

A

Exchanges ADP and ATP across inner mitochondrial membrane as they are normally not permeable. ADP enters matrix only if ATP leaves

36
Q

How is cellular respiration regulated?

A
  1. ATP via negative feedback

2. ADP (respiratory control): must have enough ADP to make ATP

37
Q

How is ATP synthase regulated?

A

Inhibitory factor I - inhibits hydrolytic activity of ATP synthase as a protective inhibitor, preventing ATP breakdown

38
Q

What are the proteins involved in uncoupling oxidative phosphorylation for the purpose of heat generation?

A

Thermogenin (UCP 1), UCP 2 and UCP 3 also involved

39
Q

What inhibits ATP synthase?

A

Oligomycin (binds to c subunit)

40
Q

What uncouples electron transport from ATP synthesis?

A

2,4-dinitrophenol (dissipates H+ gradient)

41
Q

What inhibits ATP export by inhibiting ATP-ADP translocase?

A

atractyloside, bongkrekic acid

42
Q

What inhibits Complex I of ETC?

A

rotenone, amytal

43
Q

What inhibits Complex III of ETC?

A

antymycin A

44
Q

What inhibits Complex IV of ETC?

A

CN-, N3-, CO

COB Biochemistry (12 decks)

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