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FoundSci I Unit 3 > Electron Transport Chain > Flashcards

Electron Transport Chain Flashcards

1
Q

What do the cristae of the mitochondria contain?

A

Enzymes of electron transport chain and ATP synthesis

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2
Q

Mitochondrial Genome

A

Genome small and circular
Encodes only 13 proteins of respiratory chain

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3
Q

How are mitochondrial mutations inherited?

A

Inherited exclusively in maternal manner

Mothers pass any mitochondrial mutation to all their children

Fathers do not transmit the mutation

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4
Q

Electron Transport Chain

A

Sequence of electron carriers found on cristae of the inner mitochondrial membrane

Electrons pass from carrier to carrier - carrier becomes reduced as electrons are accepted and re-oxidized as electrons pass to next carrier in line

Energy released as heat
Some energy trapped through synthesis of ATP

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5
Q

What are the 2 families of iron containing proteins?

A
  1. Cytochromes
  2. Iron-Sulfur Proteins
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6
Q

What do cytochromes contain? What happens to associated iron ion?

A

Heme prosthetic group

Associated ion reversibly oxidized and reduced - flips between Fe2+ and Fe3+

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7
Q

What do iron-sulfur proteins contain?

A

Iron-Sulfur Centers from complex III of respiratory chain

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8
Q

Coenzyme Q

A

Non-protein electron carrier

Also known as ubiquinone

Lipid soluble

Can be reduced in stages

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9
Q

Give overview of electron transport chain

A
  1. Electrons pass from NADH through Complex I to Coenzyme Q
  2. Electrons pass from Coenzyme Q to Complex III
  3. Electrons pass from Complex III to cytochrome c
  4. Electrons from cytochrome c pass to Complex IV
  5. Complex IV uses electrons to reduce oxygen to water
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10
Q

How does reduction potential change in electron transport chain? Why?

A

Reduction potential of each complex is higher than preceding complex

Free energy released by electron transfer trapped by pumping protons from matrix into intermembrane space

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11
Q

How are complex I, III, and IV arranged in membrane?

A

Vectorial Arrangement

Electrons and protons received on matrix side and protons release on intermembrane space side

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12
Q

Proton electrochemical gradient

A

Inner membrane of mitochondria is highly impermeable to protons, but minor proton leak creats electrochemical gradient

Chemical - Higher proton conc in intermembrane space than in matrix

Electrical - outer face of inner membrane becomes positive with respect to matrix face

Potential energy from driving H+ back to matrix used to make ATP

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13
Q

ATP synthase

A

F0 spans membrane - form proton pore so protons can go back into matrix

F1 projects into matrix and catalyzes phosphorylation of ADP to ATP

Proton entry coupled to rotation of F1

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14
Q

What inhibits ATP synthase?

A

Oligomycin - blocks proton channel

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15
Q

Complex I of Electron Transport Chain

A

NADH:Coenzyme Q oxidoreductase

Contains several FMN containing proteins and iron-sulfur proteins

Catalyzes reaction of

NADH + H+ + Coenzyme Q –> NAD+ + Coenzyme Q-H2

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16
Q

Complex III of Electron Transport Chain

A

Cytochrome b-c1 complex

Contains cytochromes b and c1 plus an iron-sulfur protein

Passes e- from coenzyme Q to cytochrome c

17
Q

Complex IV of Electron Transport Chain

A

Cytochrome c oxidase

Contains copper ions and cytochromes a and a3

Electrons pass from cytochrome c through copper ions and cytochromes to oxygen

High affinity for oxygen

18
Q

What is involved in delivering electrons from FADH2 to coenzyme Q? What do they not involve?

A
  1. Succinate dehydrogenase
  2. Electron-transferring flavoprotein (ETF)
  3. Mitochondrial glycerol 3-phosphate dehydrogenase

Do not involve proton pumping!

19
Q

Succinate dehydrogenase

A

FAD containing enzyme for TCA cycle

Associated with inner membrane of mitochondria

Forms complex II of ETC - electrons flow from FADH2 to Coenzyme Q

20
Q

Electron Transferring Flavoprotein (ETF)

A

Soluble protein of mitochondrial matrix

Contains FAD

Can accept electrons from other FAD dehydrogenases

ETF oxidoreductase - reoxidizes FADH2 of ETF and passes e- on to coenzyme Q

21
Q

Mitochondrial glycerol 3-phosphate dehydrogenase

A

FAD containing enzyme

Coverts glycerol 3-phosphate to dihydroxyacetone phosphate

Electrons flow from FADH2 to coenzyme Q

22
Q

What inhibits the electron transport chain?

A

Anoxia

Rotenone

Antimycin A

Cyanide

23
Q

How does Anoxia inhibit electron transport chain?

A

no oxygen, no oxidative phosphorylation

24
Q

How does Rotenone inhibit electron transport chain?

A

Inhibits complex I, block electron transfer from NADH to coenzyme Q

25
Q

How does Antimycin A inhibit electron transport chain?

A

inhibits complex III, blocks electrons transfer from coenzyme Q to cytochrome C

26
Q

How does cyanide inhibit electron transport chain?

A

inhibits complex IV, binds heme iron in complex and blocks electron transfer from cytochrome c to oxygen

27
Q

What are uncouplers?

A

Uncoupling agents short circuit mitochondria and pathway of proton flow bypasses ATP synthase

Usually protons enter mitochondrial matrix through ATP synthase and re-entry is coupled to synthesis of ATP

28
Q

2,4-dinitrophenol (DNP)

A

Potent uncoupling agent that was marked as dietary supplement. Still used for weight loss

Anionic form - drawn to positive side and picks up proton

Neutral form - drawn to alkaline side and release proton

Catalytic cycle collapses proton gradient

29
Q

What is the role of brown adipose tissues and what protein does it express?

A

Brown because of high prevalence of mitochondria and main role is to generate heat rather than ATP –> important for non-shivering thermogenesis

Express protein UCP1 (uncoupling protein 1) that forms proton conductance pathway where protons can bypass ATP synthase and energy is dissipated as heat

30
Q

How is ATP delivered to cytoplasm?

A

ATP-ADP translocase moves ATP to cytoplasm and ADP into the matrix

Phosphate carrier catalyzes either symport of Pi and a proton or antiport of OH- and Pi

31
Q

What occurs generally with defects in oxidative phosphorylation?

A

Often impact muscles and nerves - tissues with high energy demand

Mitochondrial encephalomyopathies

32
Q

MERRF

A

Defect in oxidative phosphorylation

Myoclonic epilepsy associated with ragged red fibers

Most due to point mutations in mitochondrial tRNA for lysine

33
Q

MELAS

A

defects in oxidative phosphorylation

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes

Common mutations in mitochondrial gene encoding tRNA for leucine

34
Q

Combined oxidative phosphorylation

A

Defects in oxidative phosphorylation

Autosomal recessive inheritance - nuclear genes impacted

Combined oxidative phosphorylation deficiency 1 - mutation in mitochondrial elongation factor 1 gene

Combined oxidative phosphorylation deficiency 2 - mutation in mitochondrial ribosomal protein S16

FoundSci I Unit 3 (13 decks)

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