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ELECTRON TRANSPORT CHAIN

OR RESPIRATORY CHAIN

Dr Vijay MarakalaAssistant professor

BiochemistrySIMS&RC

CONTENTS

What is ETC Localization of ETC

Function of ETC

Components of ETC

Reaction of ETC

Oxidative phosphorylati

on

Mechanism of oxidative

phosphorylation

Reducing equivalents

What is ETC?

Localization of ETC

Function of ETC

ETC collects and oxidizes reducing equivalents with liberation of energy in the form of ATP

Components of ETC

Q=Ubiquinone or coenzyme Q

Complex-I

NADH - Q oxidoreductase

NADH FMN Fe-S CoQ

Complex-II Succinate Q oxidoreductase

Succinate FAD Fe-S CoQ

Complex-III

Q- Cytochrome c oxidoreductase

CoQ Fe-S Cyt.b Cyt.c1 Cyt.c

Complex-IV

Cytochrome oxidase orCytochrome aa3

Cyt.c Cyt.aa3 O2

Reactions of ETCAccepts and transfers one hydride ionNAD+

• One H+ and 2e-

Accepts and donates two hydrogenFMN/ FAD/

Q• H2 = 2H+ and 2e-

Accepts and transfers only one electronCyt/Fe-S

• One e-

Remember

Reactions of ETCSequence of reactions

NADH+ H+ donates electrons and protons

Formation of FMNH2

Collection of electrons from FMNH2 by Fe-S proteinCollection of reducing equivalents by Co Q

Removal of electrons by cytochromes

Reduction of oxygen to water

Formation of ATP

Coupling site for ATP synthesis

Fo F1 ATPase

F0

F1

Also called ATP synthase.

Embedded in the inner

membrane

Mechanism of oxidative phosphorylation

CHEMIOSMOTIC THEORY

Peter Mitchell1920-1992

Electrochemical gradient

Proton motive force

{ {P:O ratio

No of ATP synthesized per atom of oxygen[1/2O2]

Respiratory control

The regulation of the rate of oxidative phosphorylation by ADP level is called respiratory controlP:O ratio and Respiratory

control

How cytoplasmic NADH is

transported to mitochondria?