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In The name of Almighty Allah, The Merciful, The

Beneficent

Assalam u Alykum WRWB

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Electron transport and Oxidative

Phosphorylation

Objectives

1. Define reducing equivalents and outline their sources and fates.

2. List the components of electron transport chain and describe the processof electron transport

3. Define energy, energy currency (ATP) and energy storage (creatinephosphate) ad describe the functions of Creatine phosphate and ATP.

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Energy and Free energy

All biochemical processes (reactions)involve the energy transactions

Exergonic reactions release energy

Endergonic reactions- consume energy

The actual energy available to do work(utilizable) is known as free energy.

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The free energy stored in

food stuffs is extracted in the

form of reducing equivalents.

The reducing equivalents aretransferred to ETC via different

carriers like NAD, FAD, FMN

etc

ATP is synthesized by oxidativePhosphorylation.

Reducing equivalents

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The reducing equivalents are defined as a proton plus anelectron, H+ + e-

Are transported Via Conjugate oxidant/reductant pairs

NAD-NADH

FAD-FADH2

FMN-FMNH2 Redox Potential (E

0): is the quantitative measure of tendency

of a redox pair to loose or gain electrons.

A more negative E0means a greater tendency to looseelectrons, and a positive E

0means a greater tendency to gainelectrons.

Reducing equivalents

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Electron Transport chain

(ETC) E

TC present in inner mitochondrialmembrane as four complexes

Complexes I, III and IV do the pumpingof protons

These are transmembrane proteincomplexes containing quinones, flavinnucleotides, sulfur clusters, hemes,and copper ions.

The inner membrane (IMM) isimpermeable to ions and polar

molecules. Specific transporters shuttlemetabolites such as ATP and organicions.

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4H+

INTERMEMBRANE SPACE

OH-

ATP4-

F1

Fo

3H+

MATRIXstalk

3H+

Proton gradient/Charge gradient

FMNH2

H+

complex I

CoQ

cyt bcomplex III

C1

Ccyta-a3

H+H+

O2

e-

H2O

NADH

+ H+

inner

membraneNAD

+

Pi-

e-

e-

e-

e-e-

e-

e-e-e-

H+

H+

complex IV

ADP3-

ATP4-

ATP

4-

ATP4-

OH-

OH-

ADP3-

ADP3-

ADP3-

ADP3-

ADP3-

ADP3-

ADP3-

Electron transport and Oxidative Phosphorylation

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Oxidative Phosphorylation

Definition:

Oxidative Phosphorylation isthe process in which ATP isformed as a result of the

transfer of electrons fromNADH and FADH2 to O2 by ETC.

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Mechanism of Oxidative Phosphorylation

( Chemiosmotic hypothesis and binding change model)

The Electron transport throughETC is coupled with translocation of

protons across IMM.

This results in the formation of an electrochemical gradient i.e. more H+ on

outer side of IMM than inside. The Protons flow back into the mitochondrial matrix and induce a

conformational change in the enzyme ATPase which synthesizes ATP from

ADP and Pi.

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High Energy Compounds

Definition: Certain compounds which on hydrolysisyield at least 7cal/mol free energy at pH 7.0 areknown as high energy compounds.

Classification Pyrophosphates e.g. ATP

Acyl Phosphates e.g.1,3-bisphosphoglycerate

Enol Phosphates e.g. Phosphoenolpyruvate

Thioesters e.g. Acetyl Co A

Phosphagens e.g. Creatine Phosphate

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ATP- The Energy Currency of Cell

ATP made up of adenine, ribose and a triphosphate moiety.

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ATP is a unique and most important high energy molecule in

the body due to presence of two high energy phospho-anhydride bonds.

ATP is hydrolyzed to yield energy

ATP + H2O ADP +Pi + 7.3 Cal

ATP serves as the Energy currency of Cell as it is beingconstantly utilized and regenerated in ATP-ADP cycle.

ATP also acts a phosphate donor to low energy phosphate

compounds.

ATP serves as a link between Catabolism and Anabolism inbiological system.

ATP- The Energy Currency of Cell-contd

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Creatine Phosphate (CP) is the reservoir ofenergy in muscles. CP donates its phosphate toADP to form ATP by Enzyme CreatinePhosphokinase.

When muscles contract (active muscle) energy isderived from breakdown of ATP to ADP and Pi.

ATP must be reformed quickly to supply theenergy which initially comes from creatinephosphate and subsequently from glycolysis.

In resting muscle Creatine is againphosphorylated and energy is stored as CP.

Storage forms of high Energy Phosphate

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G0

Compound (kJ/mol) ( kcal/mol)

Phosphoenolpyruvate 61.9 14.8Carbamoyl phosphate 51.4 12.3

1,3-Bisphosphoglycerate 49.3 11.8

(to 3-phosphoglycerate)

Creatine phosphate 43.1 10.3

ATP ADP + Pi 30.5 7.3ADP AMP + Pi 27.6 6.6

Pyrophosphate 27.6 6.6

Glucose 1-phosphate 20.9 5.0

Fructose 6-phosphate 15.9 3.8

AMP 14.2 3.4

Glucose 6-phosphate 13.8 3.3

Glycerol 3-phosphate 9.2 2.2

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Thank you very much

with All the best

wishes