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BIOCH 200 > Oxidative Phosphorylation > Flashcards

Oxidative Phosphorylation Flashcards

1
Q

What is the role of the electron transport and atp synthesis pathway?

A

-Convert reducing agents into ATP.

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2
Q

What is the terminal electron acceptor?

A

Molecular oxygen (O2).

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3
Q

Where does oxidative phosphorylation occur?

A

Inner mitochondrial membrane.

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4
Q

how is electron transport and atp synthesis coupled?

A

The energy released from electron transport transfers protons from the inside the mitochondrion matrix to the intermembrane space; this gradient is used to drive ATP synthesis catalyzed by ATP synthase.

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5
Q

What happens to coenzymes after reacting with the ETC?

A

They are oxidized.

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6
Q

How many mitochondria do white muscle cells have? Why is this?

A

Very few, rely on anaerobic glycolysis.

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7
Q

How many mitochondria do red muscle cells have? Why is this?

A

Many, require lots of ATP.

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8
Q

What is the important protein located on the outer mitochondrial membrane?

A

Transmembrane protein porin allows free diffusion of ions and water-soluble metabolites.

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9
Q

What is the inner mitochondrial membrane impermeable to?

A

Proteins and charged molecules/ionic substances.

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10
Q

What are the folds of the mitochondrial inner membrane called?

A

Cristae.

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11
Q

Where is the pyruvate dehydrogenase complex and enzymes of the CAC located?

A

Mitochondrial matrix.

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12
Q

What is the chemiosmotic theory?

A

The concept that the proton gradient drives ATP formation.

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13
Q

When coupled to ADP, how long does respiration occur?

A

It proceeds rapidly until all ADP is consumed.

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14
Q

What are uncouplers?

A

Stimulate the oxidation of substrates in the absence of ADP; oxygen uptake proceeds until all oxygen is depleted.

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15
Q

What kinds of oxidation-reduction centers are present on complexes I-IV?

A

Cofactors such as FAD, FMN, or Q.

Fe-S clusters, heme, and copper.

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16
Q

In what direction do electrons flow through the ETC?

A

In the direction of increasing reduction potential.

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17
Q

What do the reduction potentials of each redox center fall between?

A

The strongest reducing agent NADH and the strongest oxidizing agent O2.

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18
Q

What are the functions of coenzyme Q and cytochrome C?

A

They serve as links between different complexes of the ETC.

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19
Q

Where does Q transfer electrons to/from?

A

From complex I or II to complex III.

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20
Q

Where does cytochrome c transfer electrons to/from?

A

To complex IV from complex III.

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21
Q

What does complex IV use electrons for?

A

The reduction of O2 into water.

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22
Q

Which complexes translocate protons?

A

I, III, IV.

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23
Q

Which complex does not translocate protons? Why?

A

Complex II has a reduction potential very similar to FADH and as a result not enough energy is released to pull protons across the membrane.

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24
Q

What is complex II also known as?

A

Succinate dehydrogenase complex.

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25
Q

How many electrons enter the ETC at a time?

A

Two at a time.

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26
Q

Where are the flavin coenzymes FMN and FAH reduced?

A

FMN: I
FAH: II

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27
Q

How many electrons do the reduced FMNH2 and FADH2 donate at a time?

A

One.

28
Q

What kind of molecule is Q?

A

Lipid-soluble, integrated within the membrane,

29
Q

How many electrons can Q donate? At a time?

A

2; 1 at a time.

30
Q

What kind of protein is cytochrome C?

A

Peripheral membrane protein.

31
Q

What is the function of complex I?

A

To catalyze the transfer of two electrons from NADH to Q.

32
Q

At what point in the ETC does movement go from two-electrons at a time to one electron at a time?

A

The passover of two electrons in complex I to FMN converts the rate two one electron at a time.

33
Q

What is the fully reduced state of Q? How many electrons does it carry?

A

Ubiquinol; two electrons in QH2

34
Q

How is Q reduced? Where does QH2 release its protons?

A

It is reduced by gaining electrons from complex I, and pulls protons up from the matrix. QH2 released protons in complex III.

35
Q

How many protons are translocated in complex I? How does this occur?

A

4 protons for every pair of electrons passed from NADH to QH2; this mechanism is not clear.

36
Q

What is the function of complex II?

A

Complex II accepts electrons from succinate and catalyzes the reduction of Q to QH2.

37
Q

What is the function of complex III?

A

Complex III catalyzes the oxidation of QH2 and reduction of cytochrome c.

38
Q

How many protons are released during the oxidation of two molecules of QH2?

A

4.

39
Q

What is the function of complex IV?

A

This complex catalyzes the oxidation of reduced cytochrome c produced in III; inclludes four-electron reduction of O2 to 2H20.

40
Q

How many protons are translocated in complex IV?

A

Four.

41
Q

Why are only two protons pumped across the membrane by complex IV?

A

Two protons are required to reduce oxygen to H20.

42
Q

How many protons are pumped across the mitochondrial membrane by the ETC for every molecule of NADH oxidized?

A

10

43
Q

What is the function of ATP synthase?

A

To catalyze the synthesis of ATP from ADP+Pi.

44
Q

What are the two components of ATP synthase? What are the functions of each?

A

F1 (knob): component that contains catalytic subunits to create ATP, this region projects into the matrix.

F0 (stalk): embedded in the membrane, proton channel that drives the formation of ATP.

45
Q

How many protons are required for each ATP molecule to be synthesized?

A

3.

46
Q

How many protons does ATP synthase consume?

A

4; 3 for the production of ATP and 1 to transport Pi, ADP, and ATP across the inner membrane.

47
Q

What is the P/O ratio for NADH?

A

10/4: 2.5

48
Q

What is the P/0 ratio for succinate? Why?

A

6/4: 1.5; complex III= 4, complex IV= 2 = 6.

49
Q

What are the two purposes of catabolic pathways?

A
  1. Breakdown larger molecules into smaller building units.

2. Release and temporarily store energy in high-energy molecules (ATP/NTP/NADH/FADH2)

50
Q

What kind of pathways are oxidative?

A

Catabolic; metabolizes oxidized as cofactors are reduced, re-oxidation of cofactors generate ATP.

51
Q

How many electrons does one molecule of NADH carry?

A

2.

52
Q

How many electrons does one molecule of FADH carry?

A

2.

53
Q

What kind of proteins are complexes I-IV?

A

Integral membrane proteins.

54
Q

What is FMN?

A

Flavin mononucleotide, similar to FAD/FADH2 but does not contain adenosine.

55
Q

How many electrons can FMN carry?

A

2.

56
Q

How many electrons can an iron-sulfur cluster carry?

A

1.

57
Q

What is reduction potential?

A

Affinity for electrons.

58
Q

Describe the pathway of the ETC from start to finish:

A
  1. NADH is oxidized by Complex I, 2 electrons released. Q is reduced and transfers electrons to III. 4 Protons translocated.
  2. Complex III oxidized Q, reduces Cyt C, 4 protons translocated.
  3. Complex IV oxidizes cyt c, reduces O2 into H20. 2 protons translocated.
59
Q

What is the chemical equation for the ETC? ( 1 mol NADH)

A

NADH + H20 + 1/2 O2 + 2H +2e —> H20 + 10H + NAD+

60
Q

What kind of transport is the ETC? How?

A

Primary active transport; redox reactions cause a change in conformation to permit hydrogens.

61
Q

What is the prosthetic group in complex II?

A

FAD.

62
Q

How is newly-synthesized ATP transported from the matrix?

A

Adenine Nucleotide Translocate and Pi-H symports.

63
Q

Describe the flow chart of Ox.Phos (Low energy use)

A
  1. Low energy usage
  2. Low ADP/Pi concentrations
  3. Lower ATP Synthase activity
  4. Increased proton gradient
  5. Decreased electron transport
  6. O2 consumption is dropped.
  7. NADH and FADH2 concentrations increase. Inhibit CAC and PDH.
64
Q

Describe the flow chart of Ox. Phos (High energy use):

A
  1. High energy usage.
  2. High concentrations of ADP/Pi
  3. Increased ATP Synthase activity
  4. Decrease in proton gradient.
  5. Increased electron transport.
  6. Increased concentrations of NADH and FADH2
  7. Activation of CAC, PDH.
65
Q

Describe the process of uncoupling:

A

An integral membrane protein creates a channel for protons to cross the membrane without ATP synthesis, often generating heat.

66
Q

What tissue contains uncouplers?

A

Brown adipose tissue.

67
Q

How does oxygen consumption differ when paired to an uncoupler?

A

Consumption increases; proton gradient is dissipated faster by a channel.

BIOCH 200 (7 decks)

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