The electron transport chain (ETC) transfers electrons from electron donors like NADH to electron acceptors like oxygen via redox reactions across the inner mitochondrial membrane. This creates an electrochemical proton gradient that drives ATP synthesis. The ETC consists of 4 complexes along the inner mitochondrial membrane containing enzymes and proteins. As electrons are passed from one complex to the next, protons are pumped from the matrix to the intermembrane space. This proton gradient powers ATP synthase to generate ATP, the energy currency of cells.

1. ELECTRON TRANSPORT
CHAIN
Presented by :- Prajapati Jinal V .
CBO :- 501
M.Sc Sem :- 3
Department of life sciences ,
H.N.G.U., Patan

2. CONTENT
• Introduction
• What is ETC ?
• Location of ETC
• Component of ETC
• End of ETC

3. Introduction
• An electron transport chain is a series of complex
that transfer electron from electron donors to
electron acceptors via redox reaction and couples
this electron transfer with the transfer of protons
across a membrane .
• This creates an electrochemical proton gradient that
drives the synthesis of ATP, a molecule that stores
energy chemically in the form of highly strained
bonds .
• The molecules of the chain include peptides
,enzymes and others .

4. • The final acceptor of electrons in the electron
transport chain during aerobic respiration is molecular
oxygen although a variety of acceptors other than
oxygen such as sulfate exist in anaerobic respiration .
• ETC is the 4ᵗᵸ and final stage of aerobic respiration .
• ETC is series of highly organized oxidation – reduction
enzymes .
• The direction of energy flow level in the ETC is form a
higher to a lower energy level .

5. What is ETC ?
• ETC is a process in which the NADH and FADH₂
produced during glycolysis , ᵦ - oxidation and other
catabolic processes are oxidized thus releasing
energy in the form of ATP .
• The metabolic Pathway through which the electron
passes from one carrier to another is called
ELECTRON TRANSPORT CHAIN .

6. Location of ETC
• This chain is located in the inner mitochondria
membrane of cell.
• Protons are transported from the matrix of the
mitochondria across the inner mitochondrial
membrane to the intermembrane space located
between the inner and outer mitochondrial
membrane .
• The process takes place in units arranged on the
cristae membrane of mitochondria .

8. Components of ETC
• The various components of the respiratory chain
occur within the mitochondria .
• Complex are formed by Proteins .
• Each of the 4 complexes contain up to 40 individual
polypeptide chains .
• They perform several functions such as enzymatic
activities and trans – membrane pumps .

9. • The large trans- membrane complexes are called I , II ,
III and IV and are formed by intergal proteins .
• There are 4 complex used in electron transport chain .
1 . Complex I ( NADH dehydrogenase )
2 . Complex II ( Succinate dehydrogenase )
3 . Complex III ( Cytochrome bc₁ complex )
4 . Complex IV ( Cytochrome c oxidase )

11. 1 . Complex I (NADH dehydrogenase) :-
• There are four steps in Krebs cycle in which hydrogen
is taken up by NADᶧ to from NADH .
• The electrons of NADH are oxidized by NADH
dehydrogenase of complex I which contains tightly
bound cofactors FMN and iron sulphur centers .
• The electron passed to the next carrier CoQ of
ubiquinone which is similar to plastoquinone of the
thylakoids of chloroplasts .
• For every pair of electrons 4 protons are pumped from
the matrix to the intermembrane space .

12. 2 . COMPLEX II (Succinate dehydrogenase) :-
• Succinic acid is the only substance in Krebs cycle which
is oxidized by FAD of the enzyme Succinate
dehydrogenase of complex II to form FADH₂ .
• The hydrogen of FADH₂ enters the ubiquinone pool .
• it does not any proton during transport of electron
across the inner mitochondrial membrane .

13. 3 . Complex III ( Cytochrome bc₁ complex ) :-
• The Ubiquinone is oxidized by this complex .
• Four protons are out for every 2 electrons
transferred to the next carrier .
• The electron are transferred to cytochrome c via an
iron – sulphur center .
• Two b type cytocromes , cyt b₅₆₅ and cyt b₅₆ₒ and a
membrane bound cytochrome c₁.

14. 4 . Complex IV (Cytochrome c oxidase ) :-
• It has two copper centers – CuA and CuB and
cytochrome a and a₃ .
• The cytochrome a₃ transfer 4 electrons to oxygen
which tacks up protons to form two molecules of H₂O .
This complex is known as also terminal oxidase .
• For transfer of 2 electrons 2 protons are pumped into
the intermembrane space .
• Ubiquinone transfer electron between complex I and
II wheres cytochrome c transfer eletrons from complex
III to IV .

15. End of ETC
• The protons are shuttled to the outside of the
membrane .
• Inside of the cell membrane as it accepts electrons .
• At the end of the electron transport chain the
electrons are given to oxygen .at the same time
oxygen accepts hydrogen to form water .
• Released in this process to the phosphorylation of
ADP to from ATP .
⅟₂O₂ + 2Hᶧ + 2e˗→ H₂O

16. REFERENCES
• Textbook of PLANT PHYSIOLOGY BY : -
V . Verma
• Plant Physiology by :- LINCOLN TAIZ
EDUARDO ZEIGER
• Principle of biochemistry by :- Albert Leningher

17. THANK YOU