Lecture 22: Oxidative Phosphorylation

Question 1

Electron Transport Chain

Answer 1

1. Complex I
2. complex II
3. CoQ
4. complex III
5. cytochrome c
6. Complex IV

mitochondrial membrane

Question 2

Complex I

Answer 2

-NADH-ubiquinone oxidoreductase
-electron transfer from NADH to ubiquinone (CoQ)
-major source of ROS that damages mitochondrial DNA and causes aging
-inhibited by rotenone (pesticide)

Question 3

Rotenone

Answer 3

-pesticide
-inhibts Complex I

Question 4

Complex I reaction

Answer 4

ubiquinone + NADH = ubiquinol

Question 5

Complex II

Answer 5

-succinate dehydrogenase
-transfer e- from succinate to ubiquinone
-part of TCA cycle
-no proton transfer
-FADH2

Question 6

Complex III

Answer 6

-cytochrome bci comple
-electron transfer from ubiquinol to cytochrome c

Question 7

Cytochromes

Answer 7

-proteins with heme groups
-iron oxidized + or reduced -
-3 types in mammals (a,b,c)

Question 8

Complex IV

Answer 8

-cytochrome c oxidase
-e- ttransfer from cytochrome c to O2
-inhibited by cyanide, azide, carbon monoxide

Question 9

Inhibitors of complex IV

Answer 9

-cynaide (CN)
-azide (N3)
-Carbon monoxide (CO)

-bind to iron in heme of cyt c oxidase

Question 10

F1F0-ATP synthase

Answer 10

-inner mitochondrial membrane
-synthesizes ATP using proton gradient
-3 B subunits with different conformations (loose, open, tight)

Question 11

F1F0-ATP synthase mechanism

Answer 11

-movement of proton through F0 subunit causes rotation of F1 = conformational change of B subunits
-conformatinal changes cause synthesis and release of ATP

Question 12

Uncouplers

Answer 12

-uncouple oxidation and ATP synthesis
-break proton gradients by shuttling protons across inner membrane
-O2 consumed without ATP synthesis
-energy lost as heat
-2,4-dinitrophenol

Question 13

2,4-dinitrophenol

Answer 13

-proton ionophore
-diet pill 1930
-caused fatal hyperthermia

Question 14

UCP-1

Answer 14

-uncoupling protein
-expressed in brown adipose tissues
-inner mitochondrial membrane
-dissipates proton gradients

Question 15

Reactive Oxygen Species

Answer 15

-Cyt C oxidase catalyzes O2 to water by passing one electron at a time WITHOUT release intermediates
-small number formed from leakage from elecgron transport chain
-produced by immune cells

Question 16

NADPH oxidase (NOX)

Answer 16

-allows immune cells to produce ROS to kill bacteria

Question 17

Cell defense against ROS

Answer 17

1. superoxide dismutase and catalse
2. Glutathion peroxidase
3. antioxidants

Question 18

glutathione peroxidase

Answer 18

-glutathione as reductant
-oxidized glutathione is reduced by glutathione reductase using NADPH

Question 19

Antioxidants

Answer 19

-vitamins C, E, B-carotene
-green tea, red wine, blueberry

Question 20

ROS and diabetes

Answer 20

-too much intracellular glucose
-leads to overproduction of superoxide by mitochondria

Question 21

Vulnerable cells to ROS in diabetes

Answer 21

-cells that cannot restrict uptake of glucose:
-retina (retinopathy)
-kidney (nephropathy)
-peripheral (neuropathy)

Question 22

In oxidative phosphorylation, the final acceptor of the electrons of NADH and FADH2 is

Answer 22

O2