Lectures 28-29 Oxidative Phosphorylation

Question 1

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

Answer 1

Outer membrane

Question 2

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

Answer 2

Inner membrane

Question 3

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

Answer 3

Mitochondrial matrix

Question 4

Where does oxidative phosphorylation take place?

Answer 4

Inner membrane of mitochondria

Question 5

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

Answer 5

Coenzyme Q/Ubiquinone, Cytochrome c

Question 6

Coenzyme Q/Ubiquinone

Answer 6

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

Question 7

Cytochrome c

Answer 7

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

Question 8

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

Answer 8

FMN, Fe-S

Question 9

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

Answer 9

FAD, Fe-S

Question 10

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

Answer 10

Heme bH, bL, C1 and Fe-S

Question 11

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

Answer 11

Heme a, a3, CUa and CUb

Question 12

Name the oxidized form of coenzyme Q

Answer 12

Q, Ubiquinone

Question 13

Name the reduced form of ocenzyme Q

Answer 13

QH2, Ubiquinol

Question 14

Friedreich’s Ataxia

Answer 14

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

Question 15

Complex I of the ETC

Answer 15

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

Question 16

Complex II of the ETC

Answer 16

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

Question 17

Complex III of ETC

Answer 17

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

Question 18

Q cycle

Answer 18

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

Question 19

Complex IV of ETC

Answer 19

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

Question 20

How many protons are transported by Complex IV?

Answer 20

4 pumped protons and 4 chemical protons

Question 21

Partial reduction of oxygen forms what?

Answer 21

Free radicals

Question 22

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

Answer 22

Parkinson’s disease, Ischemia; reperfusion injury

Question 23

How do antioxidants defend against free radicals?

Answer 23

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

Question 24

Chemiosmotic hypothesis

Answer 24

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

Question 25

ATP synthase

Answer 25

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

Question 26

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

Answer 26

the beta subunits

Question 27

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

Answer 27

1. central gamma/epsilon stalk | 2. exterior column of 1 alpha, 2 beta, 1 delta subunit

Question 28

What is the function of ATP synthase?

Answer 28

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

Question 29

What is the role of the proton gradient?

Answer 29

Release ATP from the synthase

Question 30

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

Answer 30

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

Question 31

What are the three steps in ATP synthesis?

Answer 31

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

Question 32

Proton conducting unit of ATP synthase

Answer 32

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)

Question 33

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

Answer 33

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

Question 34

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

Answer 34

3 H+ power the rotation, which generates 3 ATP

Question 35

Role of ATP-ADP translocase

Answer 35

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

Question 36

How is cellular respiration regulated?

Answer 36

1. ATP via negative feedback | 2. ADP (respiratory control): must have enough ADP to make ATP

Question 37

How is ATP synthase regulated?

Answer 37

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

Question 38

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

Answer 38

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

Question 39

What inhibits ATP synthase?

Answer 39

Oligomycin (binds to c subunit)

Question 40

What uncouples electron transport from ATP synthesis?

Answer 40

2,4-dinitrophenol (dissipates H+ gradient)

Question 41

What inhibits ATP export by inhibiting ATP-ADP translocase?

Answer 41

atractyloside, bongkrekic acid

Question 42

What inhibits Complex I of ETC?

Answer 42

rotenone, amytal

Question 43

What inhibits Complex III of ETC?

Answer 43

antymycin A

Question 44

What inhibits Complex IV of ETC?

Answer 44

CN-, N3-, CO