Electron transport chainand oxidative phosphorylation

Group – 3 Shah Sunil and Groups

Respiration

Respiration Involves : Glycolysis,

Krebs cycle, Electron transport and

Oxidative Phosphorylation

INTRODUCTION

Glycolysis :Occurs in the cytoplasm.Breaks glucose into two molecules of pyruvate.

Krebs cycle :occurs in the mitochondrial matrix. degrades pyruvate to carbon dioxide.

Several steps in glycolysis and the Krebs cycle transfer electrons from substrates to NAD+, forming NADH.

NADH passes these electrons to the electron transport chain.

Mitochondria

stage 3rd of respirationOccurs in mitochondria.

Mitochondria

Outer membrane- permeable tosmall moleculesInner membrane-electron transport ATP synthase Cristae increase areaIntegrity required for

coupling ETS to ATP synthesis

Mitochondria

outer membrane relatively permeableinner membrane permeable only to

those things with specific transporters◦Impermeable to NADH and FADH2

◦Permeable to pyruvateCompartmentalization

◦Kreb's and β-oxidation in matrix◦Glycolysis in cytosol

Electron Transport System

Electron Transport Chain – is a collection of molecules embedded in the inner membrane of the mitochondria

◦Most components are proteins

Electron Transport System

Mechanism the cell that converts the energy in NADH and FADH2 into ATP.

Electrons flow along an energy gradient via carriers in one direction from a higher reducing potential to a lower reducing potential

The ultimate acceptor is molecular oxygen.

At the end of the chain electrons are passed to oxygen forming water.

Electron Transport System

An NADH molecule begins the process by “dropping off” its electron at the first electron carrier molecule

ETS

Remember: each component will be reduced when it accepts the electron and oxidized when it passes the electron down to the more electronegative carrier molecule in the chain

H2O

O2

NADH

FADH2

FMN

Fe•S Fe•S

Fe•S

O

FAD

Cyt b

Cyt c1

Cyt c

Cyt a

Cyt a3

2 H + + 12

I

II

III

IV

Multiproteincomplexes

0

10

20

30

40

50

Free e

nerg

y (

G)

rela

tive t

o O

2 (k

cl/m

ol)

Finally the electron is passed to oxygen, which is very electronegative.

The oxygen also picks up 2 H+ ions from the aqueous solution and forms water

H2O

O2

NADH

FADH2

FMN

Fe•S Fe•S

Fe•S

O

FAD

Cyt b

Cyt c1

Cyt c

Cyt a

Cyt a3

2 H + + 12

I

II

III

IV

Multiproteincomplexes

0

10

20

30

40

50

Free e

nerg

y (

G)

rela

tive t

o O

2 (k

cl/m

ol)

ETS

FADH goes through mostly the same processes, except it drops off its electron at a lower point on the ETC

H2O

O2

NADH

FADH2

FMN

Fe•S Fe•S

Fe•S

O

FAD

Cyt b

Cyt c1

Cyt c

Cyt a

Cyt a3

2 H + + 12

I

II

III

IV

Multiproteincomplexes

0

10

20

30

40

50

Free e

nerg

y (

G)

rela

tive t

o O

2 (k

cl/m

ol)

The ETC makes no ATP directly!

The ETC releases energy in a step-wise series of reactions

It powers ATP synthesis via oxidative phosphorylation.

But it needs to be coupled with chemiosmosis to actually make ATP.

Oxidative Phosphorylation

Production of ATP using transfer of electrons for energy

Some ATP is produced by substrate-level phosphorylation during glycolysis and the Krebs cycle, but most comes from oxidative phosphorylation

Oxidative phosphorylation

CONCEPT :

During oxidative phosphorylation, chemiosmosis

couples electron transport to ATP synthesis

Chemiosmosis

The Energy-Coupling MechanismInner membrane of mitochondria has

many protein complexes called ATP synthase◦ATP synthase – enzyme that makes ATP

from ADP and inorganic phosphate

It uses the energy of an existing gradient to do this.

The existing gradient is the difference in H+ ion concentration on opposite sides of the inner membrane of the mitochondria

Oxidative

phosphorylation.

electron transport

and chemiosmosis

Glycolysis

ATP ATP ATP

Inner

Mitochondrial

membrane

H+

H+ H+

H+

H+

ATP P i

Protein complex

of electron

carners

Cyt c

I

II

III

IV

(Carrying electrons

from, food)

NADH+

FADH2

NAD+

FAD+ 2 H+ + 1/2 O2

H2O ADP +

Electron transport chain

Electron transport and pumping of protons (H+),

which create an H+ gradient across the membrane

Chemiosmosis

ATP synthesis powered by the flow

Of H+ back across the membrane

ATP

synthase

Q

Oxidative phosphorylation

Intermembrane

space

Inner

mitochondrial

membrane

Mitochondrial

matrix

Chemiosmosis

Chemiosmosis – the process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work (like the synthesis of ATP)

It is the job of the ETC to create this H+ ion gradient

Oxidativephosphorylation.electron transportand chemiosmosis

Glycolysis

ATP ATP ATP

InnerMitochondrialmembrane

H+

H+H+

H+

H+

ATPP i

Protein complexof electron carners

Cyt c

I

II

III

IV

(Carrying electronsfrom, food)

NADH+

FADH2

NAD+

FAD+ 2 H+ + 1/2 O2

H2OADP +

Electron transport chainElectron transport and pumping of protons (H+),

which create an H+ gradient across the membrane

ChemiosmosisATP synthesis powered by the flowOf H+ back across the membrane

ATPsynthase

Q

Oxidative phosphorylation

Intermembranespace

Innermitochondrialmembrane

Mitochondrialmatrix

H+ ions are pumped into the intermembrane space by the ETC

The H+ ions want to drift back into the matrix.

But they can only come into the matrix easily through ATP synthase channels

A protein complex, ATP synthase, in the cristae actually makes ATP from ADP and Pi.

ATP used the energy of an existing proton gradient to power ATP synthesis.

proton gradient develops between the intermembrane space and the matrix.

Mitochondrial redox carrier

NADH Complex I Q Complex III

Complex II Complex IV

FADH O2

4 Complexes

proteins in specific order Transfers 2 electrons in specific order

◦ Proteins localized in complexes Embedded in membrane Ease of electron transfer

◦ Electrons ultimately reduce oxygen to water 2 H+ + 2 e- + ½ O2 -- H2O

Complex I

Has NADH binding site◦ NADH reductase activity

NADH - NAD+

◦ transfers to electron carriers

◦ NADH (nicotinamide adenine dinucleotide )

Passes them to coenzyme Q ( Ubiquinone )

Also receive electron from complex II

Complex II

succinate ---FAD—ubiquinone◦ Contains coenzyme Q◦ FADH2 binding site

FAD reductase activity FADH2 -- FAD conversion of succinate to

fumerate

Mitochondrial redox carriers

Complex III

ubiquinone - ubiquinone while cytochrome C gets

reduced Also contains cytochromes b NADH generates more energy

than FADH2

Complex IV

reduction of oxygencytochrome oxidaseoxygen ---> water

◦2 H+ + 2 e- + ½ O2 -- 2 H2O

◦transfers e- one at a time to oxygen

ATP Produced

◦The NADH from glycolysis may also yield 3ATP.

Krebs cycle can be used to generate about 2ATP.

Electron transport chain yield 32 ATP.

ATP Produced

About 40% of energy glucose molecule

transferred to ATP during cellular respiration

Makes approximately 38 ATP.

Conclusion /Result

OVERALL yield from

glucose 36-38 ATPs

THANK YOU

GROUP -3SHAH SUNIL KUMARGIRI JEMYTIMILSINA BINODMAJHI INDRAABDHIKINIWARSAMEMOHAMMAD ABDIKALI