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MCB 3010 > EXAM 3: OXPHO > Flashcards

EXAM 3: OXPHO Flashcards

1
Q

carbs, lipids, amino acids are the main…

A

reduced fuels for the cell

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2
Q

in oxidative phosphorylation,

A

energy from NADH and FADH2 are used to make ATP

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3
Q

if a prokaryote lives in an oxygenate environment,

A

oxidative phosphorylation can be done using the plasma membrane

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4
Q

energy of oxidation is used to

A

phosphorylate ADP

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5
Q

chemiosmotic theory

A

series of energy translations that results in energy for phosphorylation of ADP

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6
Q

energy released by electron transport…

A

is used to transport protons against the electrochemical gradient

favorable redox reactions are used to make this gradient

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7
Q

energy needed to phosphorylate ADP is provided by the

A

flow of protons down the electrochemical gradient

not result of a direct reaction

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8
Q

bacteria

A

plasma membrane

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9
Q

mitochondria

A

inner membrane

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10
Q

chloroplasts

A

thylakoid membrane

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11
Q

four distinct compartments of double membrane

A

outer

IMS

inner membrane

matrix

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12
Q

Outer membrane

A

relatively porous membrane, allows passage of metabolites

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13
Q

IMS

A

similar to cytosol; higher proton concentration, lower pH

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14
Q

inner membrane

A

relatively impermeable, proton gradient across it

location of electron transport chain complexes (including succinate dehydrogenase as part of Complex II)

infolding of membrane produces cristae - serves to increase surface area

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15
Q

matrix

A

location of CAC and parts of lipid and amino acid metabolism

lower proton concentration, higher pH

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16
Q

electron transport chain complexes

A

each complex (4) have multiple redox centers with:

FMN/FAD

cytochromes a,b,or c

iron-sulfur clusters and heme groups

Cu centers and FeCu centers

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17
Q

FMN / FAD

A

FMN: complex 1
FAD: complex 2

initial electron acceptors

can carry two electrons but transfer one at a time

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18
Q

iron-sulfur centers

A

one electron carriers

coordinated by stationary cysteines in the protein

contain variable numbers of iron and sulfur atoms; multiple ions, multiple transfers

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19
Q

cytochromes

A

proteins or subunits of complexes containing heme prosthetic groups

one electron carriers

iron coordinating porphoryin ring derivatives ring determines cytochrome type)

can be mobile or stationary

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20
Q

coenzyme Q

A

ubiquinone

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21
Q

ubiquinone

A

lipid-soluble conjugated dicarbonyl compound that readily accepts electrons

transfer 1 or 2 electrons at a time

upon accepting 2 electrons, picks up two H+ —> ubiquinol

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22
Q

ubiquinol

A

can freely diffuse in the membrane, carrying electrons with protons

mobile electron carrier transporting electrons from Complex 1 or 2 to 3

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23
Q

ubiquinone

A

Q

oxidized, hydrophobic tail in membrane

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24
Q

ubiquinol

A

QH2

fully reduced

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25
Q

free energy of electron transport

A

electrons are spontaneously transferred from molecules with lower reduction potentials to molecules with higher reduction potentials

the free energy released is used to pump protons, storing this energy as the electrochemical gradient

26
Q

COMPLEX 1

NADH: ubiquinone oxidoreductase

A

large; over 40 diff pp chains encoded by nuclear and mitochondrial DNA

27
Q

COMPLEX 1 process

A

NADH binding site on matrix side of membrane

FMN noncovalently bound, accepts 2 electrons from NADH

passes one at a time to iron-sulfur clusters

several iron sulfur clusters pass one electron at a time to ubiquinone binding site within the membrane

ubiquinone is reduced to ubiquinol

2 electrons from NADH to Q is accompanied by a transfer of 4 protons from the matrix (N) to intermembrane space (P) via transporters

reduced Q picks up 2 H+

28
Q

COMPLEX II:

SUCCINATE DEHYDROGENASE

A

succinate oxidized to fumarate

FAD accepts 2 electrons from succinate to make FADH2

electrons passed one at a time via iron sulfur centers to Q which picks up 2 H+ to become QH2

29
Q

net protons pumped at complex 1

A

4; 2 picked up for QH2

30
Q

net protons pumped at complex 2

A

0

2 dropped off by FADH2
2 picked up by Q

31
Q

why do you only get 2.5 ATP from NADH and only 1.5 ATP from FADH2?

A

NADH at complex 1 pumps 4 protons to the IMS while at complex 2 there are 0 protons pumped/ the gradient is not affected

32
Q

COMPLEX III:

UBIQUINONE; CYTOCHROME C OXIDOREDUCTASE

A

2 electrons from QH2 to reduce 2 molecules of cytochrome C

iron sulfur clusters, cytochrome b, cytochrome c

Q CYCLE: 4 additional protons added to IMS

33
Q

THE Q CYCLE

A

4 protons are added to the IMS per two electrons that reach cytochrome c

\_\_\_\_\_\_\_\_
2 molecules of QH2 become oxidized
2 cytochrome c reduced
2 protons from each QH2 goes to IMS
1 Q gets reduced using 2 electrons from QH2 oxidation
2 protons from the matrix reduce Q
34
Q

Q CYCLE PROCESS

A

Q, QH2, C bind

QH2 oxidizes, e goes to Q, e goes to C, 2H+ goes to IMS

C is reduced, leaves to complex 4; oxidized Q leaves; Q* stays

new QH2 binds, new C binds

QH2 oxidizes, e goes to Q*, e goes to C, 2H+ go to IMS

2H+ go to Q*+e

C is reduced, goes to complex 4; oxidized Q leaves; reduced QH2 leaves

35
Q

q cycle overall

A

QH2 + 2cytC (ox) + 2H+n

2 cyto c reduced
4 protons to IMS
2 protons out of matrix
oxidized 2 Q
reduced 1 QH2

net equation:

Q + 2 cytC (red) + 4H+p

36
Q

cytochrome c

A

second mobile electron carrier

soluble heme containing protein in the IMS

heme iron can be oxidized (3+) or reduced (2+)

carries single electron from Complex III to Complex IV

37
Q

COMPLEX IV:

CYTOCHROME OXIDASE

A

13 subunit membrane protein
2 heme groups; a, a3
copper ions at 2 sites; CuA, CuB

38
Q

CuA

A

two ions that accept electrons from cyto c

39
Q

CuB

A

bonded to heme a3; forming binuclear center that transfers 4 electrons to oxygen

40
Q

passing of electrons to O2 in complex 4

A

4 cytochrome C reduced from complex 3 bring electrons to complex 4 and are oxidized

4 electrons used to reduce 1 oxygen to make 2 water molecules

4 H+ picked up from the matrix; helps build gradient

4 H+ additional are pumped from matrix to IMS

reduction of O2 provides enough energy to remove 4H+ from matrix AND pump 4 H+ to IMS

41
Q

reducing oxygen equation

A

½ O2 —> H2O

2 cyto C
2 e-
2 H+ substrate
2 H+ pumped

42
Q

Complex 1 to complex 4

A

NADH + 11 H+n + ½ O2

NAD+ + 10H+p + H2O

2.5 ATP

dG = -220kJ/mol

43
Q

Complex 2 to complex 4

A

FADH2 + 6H+n + ½ O2

FAD+ + 6H+p + H2O

1.5 ATP

dG = -150 kJ/mol
(less energy from transport, less protons to IMS, less ATP made)

44
Q

proton motive force

A

proteins in the ETC created the electrochemical proton gradient by 1 of 3 means

  1. actively transporting protons across the membrane (Complex 1, Complex IV)
  2. chemically removing protons from the matrix (Complex 3 reduction of Q, reduction of oxygen Complex IV)
  3. release of protons into the IMS (Oxidation of 2 QH2 in Complex III)
45
Q

chemiosmotic model for ATP synthesis

A

electron transport sets up a proton-motive force

energy of proton-motive force drives synthesis of ATP via controlled release

46
Q

CN-

A

blocks electron transfer to oxygen;

ATP synthesis is shut down because electron transport is shut down, there is no energy from electron transport driving the proton gradient

47
Q

oligomycin

A

inhibits ATP synthesis; shuts down electron transport as well because ATP synthesis dissipates the proton gradient

48
Q

DNP

A

uncouples reactions; equalizes H+ concentrations across the membrane by allowing the gradient to dissipate

O2 is still consumed and protons are pumped to the IMS but ATP synthesis does not occur

49
Q

mitochondrial ATP synthase complex

A

2 functional units: F1, F0

50
Q

F1

A

soluble complex in the matrix

catalyzes synthesis from ADP and Pi

51
Q

F0

A

integral membrane complex

transports H+ from IMS to matrix, dissipating gradient

energy transfers to F1 to catalyze phosphorylation of ADP

52
Q

F1 hexamer

A

arranged in 3 alpha-beta dimers

dimers have 3 conformations

beta empty: nothing bound
beta ADP: ADP and Pi bound loosely
beta ATP: catalyzes ATP formation by binding product tightly

53
Q

synthase

A

no ATP

54
Q

synthetase

A

ATP

55
Q

coupling proton translocation to ATP synthesis

A

proton translocation causes a rotation of the F0 and the central shaft gamma subunit

rotation of the shaft causes a conformational change within all three alpha-beta pairs

the conformational change in one of the 3 pairs promotes the condensation of ADP and Pi into ATP

the biggest conformational change allows ATP to leave because it was previously tightly bound

56
Q

adenine nucleotide translocase

A

antiporter; ATP4- in IMS, ADP3- in matrix

57
Q

phosphate translocase

A

symporter

phosphate, H+ into matrix

58
Q

2 ways to get NADH from cytosol into mitochondria

glycolysis to ETC

A

malate aspartate shuttle

glycerol 3P shuttle

59
Q

malate aspartate shuttle

A

electrons given to malate via malate dehydrogenase which has transporter into matrix where NADH is regenerated

aspartate is transported out to cytosol to continue shuttle

NADH goes through complex I to get 2.5 ATP for each NADH

malate + NAD+ —> oxaloacetate —> aspartate —> oxaloacetate + NADH…

malate dehydrogenase; aspartate aminotransferase

60
Q

glycerol 3P shuttle

A

electrons given to dihydroxyacetone phosphate (ox) to make glycerol 3P (red) —> glycerol 3P dehydrogenase (cytosolic)

oxidation of glycerol-3P back to DHAP reduces FAD to FADH2 —> glycerol 3P dehydrogenase (mitochondrial)

electrons transferred from FADH2 to Q —> QH2 which goes to complex 3 to get 1.5 ATP for each FADH2

61
Q

regulation of OXPH

A

substrate availability:
NADH or FADH2 and ADP/Pi
due to coupling: substrates required for both ETC and ATP synthesis

inhibition leads to accumulation of NADH —> inhibits enzymes in glycolysis, CAC

inhibitor of F1

62
Q

IF1

A

ATP synthase can work in reverse when there is no proton gradient

IF1 works in matrix; prevents hydrolysis of ATP during low oxygen by preventing ATPase from turning backwards

active at lower pH when electron transport is stalled due to low O2 and H+ remains in matrix

MCB 3010 (12 decks)

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