Electron Transport and ATP Synthesis Flashcards

1
Q

How electron transport chain works

A
Reduced coenzymes (NADH, QH2) pass electrons down a reduction potential gradient, ultimately to molecular O2
O2 gains electrons and becomes water
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2
Q

Oxidative phosphorylation

A

Proton gradient drives ATP synthesis

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3
Q

Mitochondrial inner membrane

A
Highly folded (cristae) and impermeable to polar/ionic substances
Critical membrane for electron transport
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4
Q

Mitochondrial matrix

A

Contains enzymes for citric acid cycle

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5
Q

Cytosol

A

Site of glycolysis

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6
Q

Overview of electron transport

A
  1. NADH/QH2 (from TCA cycle and fatty acid oxidation) in the matrix pass electrons through many carriers, last to O2
  2. H+ are pumped to the intermembrane space, creating a charge gradient
  3. H+ flow is used to drive ATP synthesis by ATP synthase
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7
Q

Chemiosmotic theory

A

H+ concentration gradient serves as the energy reservoir for ATP synthesis

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8
Q

Uncouplers

A

Synthetic compounds which disrupt the relationship between oxidation and phosphorylation
Allow O2 to be reduced, but destroy H+ gradient as soon as it’s formed

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9
Q

Complex I of electron transport chain

A

Transfers 2 electrons from NADH to coenzyme Q

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10
Q

Mechanism of complex I

A
  1. 2 electrons are transferred from NADH to FMN (flavin mononucleotide)
  2. Single electron transfers from FMNH2 to Fe-S cluster
  3. Single electron transfers from Fe-S cluster to Q, forming QH2
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11
Q

For every 2 electrons that pass through complex I, how many H+ are pumped to intermembrane space?

A

4 H+ are pumped into intermembrane space

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12
Q

Complex II of electron transport chain

A

Also called succinate dehydrogenase (complex from step 6 of TCA cycle)
Releases very little free energy and doesn’t directly contribute to H+ gradient

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13
Q

Mechanism of complex II

A
  1. 2 electron transfer from succinate to FAD
  2. Single electron transfers from FADH2 to Fe-S
  3. Single electron transfers from Fe-S cluster to Q, forming QH2
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14
Q

Complex III of electron transport chain

A

Also called ubiquinol (QH2): cytochrome c oxidoreductase

Catalyzes transfer of electrons from QH2 to cytochrome c

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15
Q

Mechanism #1 of complex III

A
  1. 1 electron transfer from QH2 to cytochrome bL
  2. Single electron transfers from cytochrome bL to Fe-S cluster
  3. Single electron transfers from Fe-S cluster to cytochrome c
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16
Q

Mechanism #2 of complex III

A
  1. 1 electron transfer from QH to cytochrome bL to cytochrome bH
  2. Single electron transfers from cytochrome bH to Q (forming 1 QH2)
17
Q

Each QH2 that passes through complex III results in translocation of how many H+?

18
Q

Complex IV of electron transport chain

A

Also called cytochrome c oxidase

Catalyzes transfer of electrons from cytochrome c to O2

19
Q

Mechanism of complex IV

A

Single electron transfers until the final transfer to O2

Cytochrome c -> Cu A -> heme a -> heme a3 -> Cu B -> O2

20
Q

2 components of ATP synthase

A

F0 component

F1 component

21
Q

F0 component of ATP synthase

A

Pore/channel
Embedded in inner mitochondrial membrane
Consists of a and c subunits (protons pass through channel at a/c subunit interface)

22
Q

F1 component of ATP synthase

A

Catalytic portion
Anchored to inner membrane (matrix side) by F0
Contains 3 catalytic sites for ATP synthesis

23
Q

Mechanism of ATP synthase

A
  1. A proton travels through F0, causing the c-subunit “rotor” to turn one subunit
  2. When enough torque has been applied (~3 H+), the gamma subunit “jumps” 120 degrees, causing simultaneous conformational shifts in the active sites (ADP and Pi are joined together to make ATP)
24
Q

Gamma subunit of F1 component

A

Portion of F1 component that F1 rotates around (similar to spindle)

25
Adenine nucleotide translocase
Transport protein that exchanges matrix ATP for cytosolic ADP (inner membrane is impermeable to ATP)
26
Cost for transportation of ATP
1 H+/ ATP transported
27
of ATP/NADH2
2.5 ATP
28
of ATP/FADH2
1.5 ATP
29
Glycerol phosphate shuttle mechanism
NADH reduces dihydroxyacetone phosphate to glycerol 3-phosphate, which then transfers electrons to membrane-bound FAD
30
Malate-aspartate shuttle mechanism
Complicated process which uses malate (toward matrix), aspartate (toward cytosol), and redundant enzymes to shuttle 2 electron packets from NADH to the matrix