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SURVEY OF BIOCHEMISTRY Electron Transport and Oxidative Phosphorylation. Redox Centers. Zoom in on the cristae:. The Mitochondrion. ~2000 per cell. How does electron transfer work?. NADH binds to Complex I on the matrix side of the membrane. Electron Transfer with NADH.

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Presentation Transcript
how does electron transfer work
How does electron transfer work?

NADH binds to Complex I on the matrix sideof the membrane

electron transfer with nadh
Electron Transfer with NADH

FMN resembles FAD without the adenine dinucleotide group

NADH transfers its e-to redox centers in Complex I

2e- go to FMN…

electron transfer with fmnh 2
Electron Transfer with FMNH2

FMNH2 can then pass each e- to series of Fe-S clusters in a stepwise manner:

NADH transfers 2e-to FMN - a redox center in Complex I

fe s clusters in complex i
Fe-S Clusters in Complex I

Complex I contains Fe-S clusters as cofactors

coenzyme q ubiquinone
Coenzyme Q (Ubiquinone)

Electrons pass from Fe-Sclusters to a “mobile”electron carrier cofactor called Coenzyme Q

electron transfer with coq
Electron Transfer with CoQ

Coenzyme Q initially binds to Complex I to pick up 2 e- from the Fe-S clusters in Complex I

complex ii
Complex II

Succinate-Coenzyme Q Oxidoreductase

Complex II is notshownElectrons pass fromFADH2 to CoQvia Complex II

4H+ ions get pumped out of the matrix by Complex I and CoQbut not Complex II

FADH2

electron transfer with coq1
Electron Transfer with CoQ

Coenzyme Q binds to Complex III on the Intermembrane space side

One e- goes to Cytochrome c

One e- goes into the Q cycle

electron transfer with cyt c
Electron Transfer with Cyt c

Once CoQ loses its 2e-, it can dissociate from the upper region of Complex III and rebind near the matrix sideand pick up the e- it just donated!

Meanwhile, Cytochrome c carries its e- to Complex IV

electron transfer with cyt c1
Electron Transfer with Cyt c

Another CoQ carrying 2e- can bind to Complex III, passing one of its e- to Cytochrome c and one into the Q cycle and ultimately to the original CoQ molecule.

proton pumping from matrix
Proton Pumping from Matrix

4 H+ ions get pumped from matrixinto the intermembrane spaceas 2 electrons are passed through Complex I

(mechanism unknown)

NADH FMN Fe-S CoQ

complex iii and complex iv
Complex III and Complex IV

Cytochrome bc1

Cytochrome c oxidase

O2 + 4 H+ 2H2O

How does ATP get made?

chemiosmotic theory
Chemiosmotic Theory

Idea that the free energy needed to transport e- is conserved by the formation of a transmembrane proton gradient.

Proton gradient drives ATP synthesis.

complex v atp synthase
Complex V: ATP Synthase

F1F0 ATPase

F0 - water insolublew/ 8 types of subunits

F1 - water solubleperipheral membraneprotein w/ 5 types of subunits

binding mechanism in atp synthase
Binding Mechanism in ATP Synthase
  • ATP binds into the T protomer first
  • ADP and Pi bind to the L protomer
  • Supply of energy induces a conformational change
  • ATP goes to the O protomer and is released
  • ATP is synthesized at the T protomer

O = open L = loose T = tight

overview of electron transport
Overview of Electron Transport

Notice theseinhibitors of electron transport!

pros and cons of aerobic metabolism

Anaerobic Metabolism of Glucose:

C6H12O6 + 2 ADP + 2 Pi 2 Lactate + 2 H+ + 2 H2O + 2 ATP

Aerobic Metabolism of Glucose:

C6H12O6 + 32 ADP + 32 Pi + 6O2 6 CO2 + 38H2O + 32 ATP

Pros and Cons of Aerobic Metabolism

PRO: Aerobic metabolism is up to 16x more productivethan anerobic metabolism!

pros and cons of aerobic metabolism1
Pros and Cons of Aerobic Metabolism

O2 + e- O2-•

Superoxideradical

Other harmful possibilities:

H2O2 + Fe2+ •OH + OH- + Fe3+

O2-• + H2O2 O2 + H2O + •OH

CON: Aerobic metabolism, with its high efficiency, tendsto produce free radicals of oxygen!

superoxide dismutase sod

2O2-• + 2H+ O2 + H2O2

Otherpotentialantioxidants

Superoxide Dismutase (SOD)
  • An inherent antioxidant enzyme

SOD

2H2O2

Catalase

2 H2O+ O2