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BIOL 2421 - Cellular Biochem > 20. the ETC > Flashcards

20. the ETC Flashcards

1
Q

define oxidative phosphorylation

A

the culmination of energy-yielding metabolism in aerobic organisms

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2
Q

what type of electron carriers were produced by glycolysis, pyruvate oxidation, and CAC

A

reduced electron carriers (NADH and FADH2)

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3
Q

what happens to the electrons of the reduced electron carriers during the ETC

A

the electrons are passed to proteins, and oxygen is the ultimate electron acceptor, and the energy of oxidation is used to make ATP

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4
Q

where is the ETC

A

in the inner mitochondrial membrane

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5
Q

for the ETC, where in the cell do the reduced electron carriers arrive

A

in the mitochondrial matrix side of the IMM

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6
Q

in the ETC where in the cell is the H+ gradient generated

A

in the intermembrane space of the mitochondria

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7
Q

for the ETC where in the cell does the ATP go as it’s made from ATP synthase

A

mitochondrial matrix

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8
Q

what two processes make up oxidative phosphorylation

A

the ETC and chemiosmosis

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9
Q

what happens once O2 accepts the electrons at the end of the ETC

A

water is made

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10
Q

T or F: electron movement through the ETC is spontaneous

A

true

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11
Q

why is electron movement through the ETC spontaneous

A

each subsequent carrier has a higher reduction potential (ie each carrier wants the electrons more) until we reach oxygen

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12
Q

how is the energy extracted from the oxidation reactions of the ETC conserved

A

the energy is used to establish a proton gradient across the IMM

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13
Q

what is the purpose of establishing a proton gradient across the IMM

A

the electrochemical potential will drive ATP synthesis, and the conversion to ATP is unfavorable which is why it requires the energy input from the gradient

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14
Q

T or F: ATP production in the ETC is considered to be substrate level phosphorylation

A

false; because the ATP production is not a result of a direct reaction between ADP and some high-energy phosphate carrier

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15
Q

describe the outer membrane of the mitochondria

A

relatively porous, allows passage of metabolites but not proteins through large transmembrane porin complexes

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16
Q

describe the IMM of the mitochondria

A

similar environment to the cytosol, high H+ concentration than the matrix

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17
Q

describe the inner membrane of the mitochondria

A

impermeable to almost all metabolites (they need specific transporters to pass), have cristae which increase SA, location of ETC and ATP synthase

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18
Q

describe the matrix of the mitochondria

A

lower H+ concentration than the IMM, location of the CAC and PDH complex

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19
Q

define redox pair

A

an electron donor and an acceptor in a redox reaction

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20
Q

what is ∆Eo′

A

standard reduction potential

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21
Q

what are the units for ∆Eo′

A

volts (V)

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22
Q

what is the formula for finding ∆Eo′ from the redox reaction

A

∆Eo′ = Eo′(electron acceptor) -Eo′(electron donor)

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23
Q

what does a high ∆Eo′ value mean

A

greater electron affintiy

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24
Q

how is ∆Eo′ related to ∆Go′

A

∆Go′ = –nF∆Eo′

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25
Q

what is F in the reaction ∆Go′ = –nF∆Eo′

A

Faraday’s constant (96,480 J/V x mol)

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26
Q

what is the ∆Eo′ for the entire ETC

A

1.14 V

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27
Q

what are the three key mechanisms of electron transfer through the respiratory chain

A

direct transfer (ie Fe3+ to Fe2+), transfer as an H (H+ and e-), and transfer as a hydride ion (:H- has 2 e-)

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28
Q

define reducing equivalent

A

used to designate a single electron equivalent transferred in a redox reaction

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29
Q

other than NADH and FADH2, which carriers are used in the ETC

A

ubiquinone, cytochromes, and iron-sulfur proteins

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30
Q

how many electrons can quinone carry

A

1 or 2

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31
Q

how many electrons can quinone pick up

A

1 for each electron

32
Q

T or F: ubiquinone is mobile

A

true

33
Q

list the other two names of ubiquinone

A

coenzyme Q, or Q

34
Q

what is ubiquinone called when reduced

A

QH2

35
Q

what are cytochromes

A

proteins with iron containing heme prosthetic groups

36
Q

how many electrons can cytochromes carry

A

1

37
Q

how many types of cytochromes does the mitochondria have

A

3: a, b, and c

38
Q

T or F; cytochromes absorb visible light

A

true

39
Q

why do cytochromes absorb visible light

A

due to the ringed delocalized electrons

40
Q

describe the structure of each cytochrome

A

a has a long isoprenoid tail, and both a and b are tightly bound to large protein complexes, but c is not

41
Q

what characteristic does cytochrome c have since it isn’t attached to a large protein complex like a and b are

A

it associates with the outer surface of the IMM through electrostatic interactions, allowing it shuttle electrons between two less mobile complexes

42
Q

describe the structure of iron-sulfur proteins

A

iron atom is associated with a sulfur atom (from Cys, inorganic sulfur, or both). Together they make an Fe-S center of varying complexity

43
Q

how many electrons can Fe-S proteins carry

A

1

44
Q

how many Fe-S proteins are involved in the ETC

A

at least 8

45
Q

how are the electron carriers of the ETC organized

A

organized into membrane-embedded supramolecular complexes

46
Q

how many supramolecular complexes are there in the ETC

A

4

47
Q

what are the two pathways of the supramolecular complexes of the ETC

A

1 to 3 to 4

2 to 3 to 4

48
Q

T or F: electrons move from complex 1, through 2 and 3, and then to 4

A

false; electrons will never go through all 4. They either go 1,3,4 or 2,3,4

49
Q

complex I: what carriers do electrons move between

A

NADH to Q

50
Q

complex I: describe the structure

A

45 dif polypeptide chains and 8 Fe-S centers

51
Q

complex I: where is the NADH binding site

A

the matrix side

52
Q

complex I: what happens to the electrons when NADH binds to its binding site

A

noncovalently found flavin monocucleotide (FMN) accepts the 2 electrons. Fe-S centers pass electrons one at a time towards the Q binding site

53
Q

complex I: describe the exergonic and endergonic transfers that occur as electrons move

A

exergonic: hydride ion and a proton from the matrix go to Q
endergonic: transfer of 4 protons from the matrix to the IMM against their gradient

54
Q

complex I: how many protons are pumped into the IMM

A

4

55
Q

complex II: which carriers move the electrons

A

succinate to Q

56
Q

complex II: describe the structure of succinate dehydrogenase

A

4 subunits: 2 membrane bound and 2 extending into the matrix

57
Q

complex II: describe the electron movement

A

succinate donates electrons to FAD to produce FADH2, then they move through a series of Fe-S centers until they reach the Q binding site where we get QH2

58
Q

complex II: how many protons are moved into the IMM

A

ZERO

59
Q

complex III: what carriers do electrons move between

A

ubiquinol to cytochrome C

60
Q

complex III: describe the two key transfers that occur

A

exergonic of two electrons from ubiquinol (QH2) to two molecules of soluble cytochrome c

endergonic of 4 protons into the IMM against their gradient

61
Q

complex III: how many protons are pumped into the IMM

A

4

62
Q

complex III: how many electrons can cytochrome c hold at a time

A

only 1

63
Q

complex III: what is the result of cytochrome c only being able to hold 1 of the 2 electrons at a time

A

QH2 will go back and forth as it shuttles electrons and protons across (the Q cycle)

64
Q

the Q cycle: describe the first half of the process

A

one QH2 on the IMS side releases two protons into the IMS. One of the lost electrons moves towards the matrix and the other goes to cytochrome c. This leaves us with Q, and a partially reduced cytochrome c

65
Q

the Q cycle: describe the second half of the process

A

a Q on the matrix side accepts the lone electron (Q-) and a second molecule of QH2 repeats the process (2 H+ donated to IMS, one electron to Q- = QH2 and one to cytochrome c = fully reduced cytochrome c)

66
Q

the Q cycle: describe the net effects

A

one QH2 becomes fully oxidized (two were, but we produced one QH2 too), two cyt c molecules are reduced (one electron received by each), 4 H+ into the IMS, two protons from the matrix are consumed

67
Q

complex IV: what carriers are involved

A

cytochrome c to O2

68
Q

complex IV: what is the role of copper

A

copper is complexed with two SH groups from Cys to form a binuclear center called CuA

69
Q

complex IV: what is the role of heme

A

CuA will donate the electron from cytochrome c through some heme groups, and the hemes will pass the electron to O2

70
Q

complex IV: how many protons are pumped into the IMM for every electron pair

A

2

71
Q

from the 2 electrons donated from NADH, what is made?

A

10 H+ into the IMS, 1 H2O made

72
Q

from the 2 electrons from FADH2, what is produced?

A

6 H+ into the IMS, 1 H2O made

73
Q

what is the affect of the difference in the number of the H+ pumped into the IMS from NADH and FADH2

A

the difference in the H+ pumped into the IMS impacts the amount of ATP made
(NADH –> 2.5 ATP)
(FADH2 –> 1.5 ATP)

74
Q

which electron carrier is better at making ATP; NADH or FADH2

A

NADH

75
Q

describe the two components of the proton motive force

A
  1. the chemical potential energy due to the dif in conc. of H+ across a membrane
  2. the electrical potential energy die to the separation of charge when an H+ moves across a membrane without a counterion
76
Q

describe regulation of the ETC

A
  • ATP is only formed as fast as it can be used

- glycolysis, pyruvate oxidation, CAC, ETC, and chemiosmosis are all accelerated or inhibited together

BIOL 2421 - Cellular Biochem (21 decks)

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