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Chemistry S2 > Test 3: ETC and ATP > Flashcards

Test 3: ETC and ATP Flashcards

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1
Q

What 3 types of work does a cell do?

A
  • mechanical work
  • transport work
  • chemical work
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2
Q

What is ATP?

A
  • Adenosine TriPhosphate
  • nucleotide with unstable phosphate bonds that the cell hydrolyses for energy to drive endergonic reactions.
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3
Q

What does ATP consist of?

A

ATP (nucelotide):
- 3 phosphate groups
- ribose
- adenine

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4
Q

How is energy released from ATP?

A

terminal phosphate bond is hydrolysed:
- inorganic phosphate group (Pi) is removed
- ADP is produced

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5
Q

Explain the strength of phosphate bonds of ATP. Why?

A
  • called “high-energy phosphate bonds”
  • weak covalent bonds
  • unstable

weak because each phosphate group has a negative charge –> instability due to repulsion

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6
Q

The hydrolysis of ATP is coupled directly to what kind of processes? How?

A
  • endergonic processes
  • by transferring the phosphate group to another molecule
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7
Q

What happens when a phosphate group is transferred to another molecule?

A

the molecule is:
- phosphorylated
- more reactive!

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8
Q

How can ATP be synthesised? By what processes?

A
  • glycolysis
  • oxidative phosphorylation
  • substrate-level phosphorylation
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9
Q

What is substrate level phosphorylation? How does it occur? What does it form?

A
  • chemical reaction
  • forms ATP
  • direct transfer and donation of phosphoryl group (-PO32-) to ADP
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10
Q

Where does substrate level phosphorylation occur? Under what conditions?

A

location: cytoplasm (glycolysis)
conditions: aerobic and anaerobic

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11
Q

What is the primary difference between substrate level phosphorylation and oxidative phosphorylation?

A

substrate level phosphorylation:
- oxidation and phosphorylation are not joined!

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12
Q

What is oxidative phosphorylation? What does it form? What happens?

A
  • chemical process
  • forms ATP
  • transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers
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13
Q

What enzyme complexes take part in oxidative phosphorylation?

A
  • ATP synthase
  • the electron transport chain
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14
Q

Where does oxidative phosphorylation take place in eukaryotes?

A

mitochondria

inner mitochondrial membrane: ETC, ATP synthase

mitochondrial matrix: pyruvate dehydrogenase complex, cirtric acid cycle, fatty acid oxidation

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15
Q

What is the ETC?

A
  • set of membrane proteins allowing for oxidative phosphorylation of O2.
  • highly exergonic reduction of O2 by NADH and FADH2
  • occuring in a number of electron transfer reactions
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16
Q

How is the ETC organized?

A

4 complexes:
I: NADH-coenzyme Q reductase / NADH dehydrogenase
II: succinate-coenzyme Q reductase / succinate dehydrogenase
III: coenzyme Q reductase
IV: cytochrome C reductase

17
Q

Where are all of the ETC complexes located?

A

embedded in the inner mitochondrial membrane

18
Q

Explain how electrons are carrier (of both NADH and FADH2)

A

NADH:
I –> II (+ ‘ubiquinone’ coenzyme Q) –> III –> IV

FADH2:
II (+ ‘ubiquinone’ coenzyme Q) –> III

19
Q

What is ‘ubiquinone’?

A

‘ubiquinone’ = reduced form of coenzyme Q

20
Q

Where are FADH2 electrons generated?

A

in the succinate dehydrogenase (Citric Cycle)

21
Q

What is an oxidation-reduction couple? State examples.

A

Pair of molecules of which one is reduced and the other is oxidized.
- lactate & pyruvate
- NADH & NADH+
- FADH2 & FAD

22
Q

What is complex I? How many electrons does it transfer? From what to what?

A

NADH-Coenzyme Q reductase / NADH dehydrogenase
- transfers 2 electrons from NADH to coenzyme Q
- contains FMN prosthetic group
- NADH + FMN –> NAD+ +FMNH2

23
Q

What is complex II? What is it composed of?

A
  • succinate dehydrogenase
  • enzyme of the citric acid cycle
  • 4 subunits (2Fe-S and 2 FAD)
24
Q

State the overall reaction for complex II.

A

succinate + CoQ –> fumarate + CoQH2

25
Q

What is complex III? What is it composed of?

A

coenzyme Q-cytochrome c reductase
- passes electrons by the Q-cycle
- 2 b-type cytochromes, 1 c-type cytochrome

26
Q

What is a cytochrome?

A
  • iron-containing electron transferring proteins
  • heme proteins
27
Q

What do cytochromes undergo?

A

reduction:
all: Fe3+ –> Fe2+
cytochrome a3: Cu2+ –> Cu+

28
Q

What is complex IV? What is it composed of?

A

Cytochrome c oxidase
- a proton pump

  • 2 heme centers, cytochrome a, cytochrome a3 and 2 copper proteins
29
Q

Explain the reaction process with cytochrome IV.

A
  • Cytochrome IV + O2 –> … + 2H2O
  • O2 is reduced into H2O
30
Q

What does the chemiosmotic theory create?

A
  • an electrical gradient (more e- on the outside of the membrane)
  • pH gradient (outside is more acidic)
31
Q

What is Complex V? What does it do?

A

ATP synthetase / ATPase
- synthesizes ATP through the proton gradient (proton motive force) generated by the ETC
- spontaneous H+ flux

32
Q

Explain the cycle of ATP-ase. What are the three conformations?

A
  • driven by H+ flow
  • conformation of each B subunit changes (as it interacts with the rotating shaft)

loose conformation: active site can bind ADP+Pi
tight conformation: substrates bound and ATP is formed
open conformation: favours ATP release

33
Q

What would happen if no membrane potential or pH gradient exists?

A

the reverse reaction would occur:
- ATP hydrolysis

34
Q

State examples of inhibitors of ATPsynthase. What do they do?

A

block H+ transport coupled to ATP synthesis / hydrolysis:
- ogliomycin
- DCCD

35
Q

What is the energetic yield of ETC (oxidative phosphorylation)?

A

Oxidation of NADH: 3ATP (ADP and Pi)
Oxidation of FADH2: 2ATP (ADP and Pi)

Chemistry S2 (5 decks)

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