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Chapter 18 Oxidative phosphorylation.  the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers  take place in mitochondria, the major source of ATP in aerobic organisms

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chapter 18 oxidative phosphorylation
Chapter 18 Oxidative phosphorylation

the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers

take place in mitochondria, the major source of ATP in aerobic organisms

the culmination of a series of energy transformations that are called cellular respiration or simple respiration (p. 503)

Electron-motive force

NADH-Q oxidoreductase, Q-cytochrome c oxidoreductase,

 cytochrome c oxidase

Proton-motive force

Phosphoryl transfer potential (ATP synthase)

Proton gradients are an interconvertible currency of free energy in biological systems

slide2

§18.1Oxidative phosphorylation in eukaryotes takes place in

mitochondria:2 m in length and 0.5 m in diameter

Kennedy and Lehninger

(TCA cycle,

fatty acid oxidation)

quite permeable

voltage-dependent anion channel (mitochondrial porin)

(oxidative phosphorylation)

Impermeable

a large family of transporters shuttles metabolites

matrix side (N side)

cytosolic side (P side)

slide3

§18.2Oxidative phosphorylationdepends on electron transfer

Measurement of redox potential (E0’)

 to evaluate electron-transfer potential (G°’)

1M reduction potential of H+:H2 couple = 0

slide4

slide5

G°= -nF E0 faraday (23.05 kcal mol-1V-1)

½ O2 + NADH + H+ H2O + NAD+

G0' = - 52.6 kcal mole-1p. 508

Release energy is used

1. proton gradient formation ATP synthesis

ATP hydrolysis G0' = -7.3 kcal mole-1

2. transport metabolites across the Mito. membrane

H+matrixcyto: 5.2 kcal mole-1

△ G = RT ln(C2/C1) + ZF △V

pH lower

slide6

§ 18.3 Four complexes in respiratory chain

Respirasome

1,2,3

1,2,4 ?

Electron affinity high

slide7

Nelson

does not pump protons

slide8

P

N

slide9

Respiratory chain complexes separation

Nelson

ATP synthase (complex V)

In vitro, hydrolytic activity

slide10

Universal electron acceptors:

NADH and NADPH:

are water soluble, can’t cross inner Mito. membrane

carry e- from catabolic rxs. vs. supply e- to anabolic rxs.

[reduced form]/[oxidized form]

Nelson

hydride

UV

p. 499

slide11

Universal electron acceptors:

Flavin nucleotides (FMN or FAD):

are bound to flavoproteins which determine the reduction potential of a

flavin nucleotide

a part of the flavoprotein’s active site

flavoproteins can participate in either one- or two- electron transfer

Nelson

slide12

Nelson

Universal electron acceptors:

Ubiquinone (coenzyme Q, Q):

a lipid-soluble molecule

can accept one or two e-

carry both e- and proton

Q pool:

a pool of Q and QH2

exist in the inner Mito.

membrane

slide13

Nelson

Universal electron acceptors:

iron-sulfur proteins:one-electron transfer

non-heme iron proteins

without releasing or binding protons

p. 511

1 Fe — 4 Cys 2 Fe — 2 S — 4 Cys 4 Fe — 4 S — 4 Cys

Rieske iron-sulfur proteins:

2 His residues replace 2 cys residues

Phosphorylation at His

slide14

Universal electron acceptors:

cytochromes: a, b, c three classes in Mito.

one-electron transfer

Nelson

Covalently associated to proteins

Vinyl group

560 nm

550 nm

(C17)

The standard reduction potential (p. 507)

The longest-wavelength

600 nm

slide16

1. NADH-Q oxidoreductase(NADH dehydrogenase, complex Ⅰ)

NADH + Q + 5H+matrix NAD+ + QH2 + 4H+cytosol

slide19

Q cycle:

semiquinone radical anion

slide21

3. Q-cytochrome c oxidoreductase(cytochrome bc1 complex; cytochrome reductase; complex Ⅲ)

His replace cys

1e-

1e-

Q 3(hemes)cytochrome c

1(2Fe-2S)

during Q cycle

4 cyt c red 8 h n o 2 4 cyt c ox 2 h 2 o 4 h p

4. Complex Ⅳ: Cytochrome c oxidase

e- from cytosol to O2

2 heme a, 3 copper ions 3 subunits

CuA/CuA heme a

 heme a3  CuB  O2

ferric/ferrous

cupric/cuprous

4 cyt cred +8 H+N + O2 4 cyt cox + 2 H2O + 4 H+P

Nelson

?

slide23

1st e-

Cupric (Cu2+)

 Cuprous (Cu+)

2nd e-

Ferric (Fe3+)

 Ferrous (Fe2+)

3th and 4th e-

proton transport by complex 4 cyt c red 8 h n o 2 4 cyt c ox 2 h 2 o 4 h p
Proton transport by complex Ⅳ4 cyt cred + 8 H+N + O2 4 cyt cox + 2 H2O + 4 H+P

G0’

4 H+  5.2 kcal/mole(p. 509)

 2  23.06  0.82

(Tab. 18.1)

Charge neutrality and

Conformational changes

(p. 517)

slide26

only electrons transfer,

no protons transport

NADH + 11 H+N + ½ O2 → NAD+ + 10 H+p + H2O

FADH2 6

reactive active oxygen species r a oss
Reactive (active) oxygen species (R[A]OSs)

Danger lurks in the reduction of O2

 superoxide radical (·O2-), peroxide (O22-), hydrogen peroxide (H2O2),hydroxyl radical (OH·),singlet oxygen (O21)

 superoxide dismutase (SOD): Cu/Zn-; Mn-; Fe-

catalase (CAT): 2 H2O2  O2 + 2H2O

a heme protein

peroxidase: H2O2 + RH2  2 H2O + R

[ascorbate or glutathione peroxidase]

SOD: 2 ·O2- + 2H+ O2 + H2O2

Dismutation: a reaction in which a single reactant

is converted into two different products

Antioxidant vitamins:

Vit C:

Vit E: lipophilic, avoid lipid peroxidation

slide28

Radical ·Q– from complex Ⅰto QH2

QH2 to bL of complex III

Nelson

p. 722

Also from pentose phosphate pathway

slide29

TypeⅠ: insulin dep.

a paucity of pancreatic  cells

TypeⅡ: non-insulin dep.

slow to develop,

in older, obese individuals

insulin is produced, but some feature of

the insulin-response system is defective

The characteristic symptoms of both types:

polydipsia, polyuria, glucosuria

Aerobic metabolism 

 More ROS

 More protective enzymes were induced