Bioenergetics Flashcards

1
Q

How O2 changed the planet:

A
  1. Redox buffers filled (releasing O2 into air)
  2. Respiration evolved to O2 (more efficient)
  3. Metal ion availability (solubility linked to redox)
  4. O2->O3 (shields UV)
  5. Many species died (O2 is toxic)
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2
Q

O2 Thermodynamics and Kinetics

A

Thermodynamically - unstable (2e- reduction favorable)

Kinetically - stable (spin-state change required)

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3
Q

H2O/O2 EM7

A

820mV

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4
Q

NADH/NAD+ EM7

A

-320mV

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5
Q

Nernst equation

A
E = E˚ - (RT/nF)ln(red/ox)
E = E˚ - 59log(red/ox)
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6
Q

∆G to ∆E conversion

A
∆G = -nF∆E = n-96.5∆E
100meV = -9.6kJ/mol
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7
Q

Energy to pump proton and ATP synthesis

A

1 proton = 200meV = -19.2kJ/mol
1 ATP = 50kJ/mol
therefore: 2.5 protons = 48kJ/mol = 1 ATP

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8
Q

Redox Potentials in Photosynthesis

A

680nm = 1.82eV

PD1/PD1+ = 1.25V
Ph/Ph- = -500mV
Qa/Qa- = -150mV
Tyr-/Tyr = 1.2V
Qb/Qb- = -20mV
Qb-/QbH2 = -20mV
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9
Q

Energy transfer in photosynthesis

A

Of 1.82eV from red photon:

  1. 600mV lost stabilising charge separation
  2. 150-200meV used to produce free QH2 and other steps in charge accumulation (S0-S1)
    a. for every e- transferred, 1H+ is taken from stroma and released to lumen (chemical protons), the energy stored is ~200mV
  3. Energy needed to do water oxidation and quinone reduction is ~820meV (ΔE = -819meV at functional conditions)
  4. Energy used = 600+200+820 = 1.62eV
    a. Remainder: driving force available for water oxidation by the oxidised S4 state and O2 release (~200meV)
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10
Q

Overall reaction in PSII

A

2H2O + 2PQ -> 2PQH2 + O2

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11
Q

Overall reaction in Cytochrome C Oxidase

A

4Cytc (Fe2+) + O2 + 4H+ 4Cytc (Fe3+) + 2H2O

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12
Q

Enzyme name for PSII

A

Water/Plastoquinone photo-oxidoreductase

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13
Q

Enzyme name for Cytc Oxidase

A

Ferrocytochrome c/oxygen oxidoreductase

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14
Q

1 Cytochrome oxidation (EH)

A

300mV

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15
Q

1 Oxygen reduction (EH)

A

800mV

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16
Q

Summary of Cyt C Oxidase

A
  1. O2 binds open 6th ligand position of heme a3
  2. O2 is reduced by 4e- in 1 shot:
    a. 2e- from heme a3 (Fe4+=O), 1e- from CuB and 1e- from Tyr244
  3. Cytc provides 4e- to reduce active site back to R state to bind next O2
    a. (Tyr˙, Fe4+, Cu2+, Fe3+)
  4. Each reduction step involves uptake of a chemical proton from the matrix