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Flashcards in Electron Transport and ATP Synthesis Deck (30):
1

How electron transport chain works

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

2

Oxidative phosphorylation

Proton gradient drives ATP synthesis

3

Mitochondrial inner membrane

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

4

Mitochondrial matrix

Contains enzymes for citric acid cycle

5

Cytosol

Site of glycolysis

6

Overview of electron transport

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

7

Chemiosmotic theory

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

8

Uncouplers

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

9

Complex I of electron transport chain

Transfers 2 electrons from NADH to coenzyme Q

10

Mechanism of complex I

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

11

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

4 H+ are pumped into intermembrane space

12

Complex II of electron transport chain

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

13

Mechanism of complex II

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

14

Complex III of electron transport chain

Also called ubiquinol (QH2): cytochrome c oxidoreductase
Catalyzes transfer of electrons from QH2 to cytochrome c

15

Mechanism #1 of complex III

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

16

Mechanism #2 of complex III

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

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

4 H+/QH2

18

Complex IV of electron transport chain

Also called cytochrome c oxidase
Catalyzes transfer of electrons from cytochrome c to O2

19

Mechanism of complex IV

Single electron transfers until the final transfer to O2
Cytochrome c -> Cu A -> heme a -> heme a3 -> Cu B -> O2

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2 components of ATP synthase

F0 component
F1 component

21

F0 component of ATP synthase

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

22

F1 component of ATP synthase

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

23

Mechanism of ATP synthase

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

Gamma subunit of F1 component

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)

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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