The electron transport chain is located in the inner mitochondrial membrane and is responsible for generating ATP through oxidative phosphorylation. It works by transporting electrons from NADH and FADH2 through a series of protein complexes and carriers, establishing a proton gradient across the membrane. As protons flow back through ATP synthase, ATP is generated from ADP and phosphate. Overall, the electron transport chain uses oxygen as the final electron acceptor to oxidize nutrients, produces water, and harnesses the energy to generate three ATP per NADH or FADH2 molecule used.

1. Electron transport chain(ETC)

2. Introduction
Discovery
 In 1961, an American biochemist, Albert
Lehninger, discovered that the citric acid cycle
and the electron-transfer chain of enzymes (where
1 NADH makes 3 ATPs) are located within each
cell’s mitochondria.
 And each cell has many mitochondrion power
plants that produce an energy output which can
be measured.

3. Importance and Location
•Importance:
These are the mechanism by which
NADH plus H+ and FADH2 are used to
generate ATP
•Location:
Inner mitochondrial membrane
(showing my mammalian bias)

5. ETC
 The majority of the energy conserved during
catabolism reactions occurs near the end of the
metabolic series of reactions in the electron
transport chain.
 The electron transport or respiratory chain
gets its name from the fact electrons are
transported to meet up with oxygen from
respiration at the end of the chain.
 The overall electron chain transport reaction is:
2 H+ + 2 e+ + 1/2 O2 ---> H2O + energy

6. ETC
 Notice that 2 hydrogen ions, 2 electrons,
and an oxygen molecule react to form as a
product water with energy released in an
exothermic reaction.
 This relatively straight forward reaction
actually requires eight or more steps. The
energy released is coupled with the
formation of three ATP molecules per every
use of the electron transport chain

7. ETC
 The Electron transport system contains
mainly six components arranged in the
following sequence
1.NAD (Nicotinamide adino dehydragenase)
2.FAD ( Flavo adino dehydragenase)
3.cytochrome B
4.cytochrome C
5.cytochrome A and
6.cytochrome A3

9. Initiation of Electron Transport Chain:
 Once the NADH has been made from a
metabolite in the citric acid cycle inside of the
mitochondria, it interacts with the first complex 1
enzyme, known as NADH reductase.
 This complex 1 contains a coenzyme flavin
mononucleotide (FMN) which is similar to FAD.
 The sequence of events is that the NADH, plus
another hydrogen ion enter the enzyme complex
and pass along the 2 hydrogen ions, ultimately to
an interspace in the mitochondria.

10.  These hydrogen ions, acting as a pump, are
utilized by ATP synthetase to produce an
ATP for every two hydrogen ions produced.
 Three complexes (1, 3, 4) act in this
manner to produce 2 hydrogen ions each,
and thus will produce 3 ATP for every use
of the complete electron transport chain.

11. Oxidation of FAD & NADH
occurs by the following steps
Step1:
The initiation of electron transport system is
the removal of hydrogen from the substrate
by enzyme dehydrogenase
2H 2H+ + 2e-the
hydrogen atom becomes ionized into
protons+ and electrons-

12.  Step2:
The hydrogen ion reduces the co-enzyme NAD
NAD + 2H+  NADH +H+
 Step3:
NADH is oxidized into NAD by transferring its
hydrogen ion to FAD which act as the hydrogen
carrier.
 Step4:
From FAD each hydrogen ion is discharged in
the cell fluid and electrons are passed on the
cytochromes B,C,A and A3

13.  Step5:
From the cytochromes the electrons are
given to the enzyme cytochrome oxidase.
 Step6:
The cytochrome oxidase finally discharge
electron to oxygen.This oxygen units with
hydrogen ions forming water.

14. Global ETC With ATP

15. Global ETC With ATP
Site 1
NADH + H
NAD
FMN FeS1 FeS2 FeS3 FeS4 FeSn Q b562 b566 FeS cyt c1 cyt c
FeS
FAD
Site 2
FADH2 FAD
Site 3 Site 4
cyt a cyt a3
1/2 O2
H2O
ADP + Pi ATP ADP + Pi ATP ADP + Pi ATP

16. Step 1: Proton gradient is built up as a result of NADH (produced from oxidation
reactions) feeding electrons into electron transport system.

17. Step 2: Protons (indicated by + charge) enter back into the mitochondrial matrix
through channels in ATP synthase enzyme complex. This entry is coupled to ATP
synthesis from ADP and phosphate (Pi)

18. Step 3: The cytochrome oxidase finally discharges electron to oxygen. This
oxygen units with hydrogen ions forming water

19. Conclusion
1. Protons are translocated across the membrane, from the
matrix to the intermembrane space
2. Electrons are transported along the membrane, through a
series of protein carriers
3. Oxygen is the terminal electron acceptor, combining
with electrons and H+ ions to produce water
4. As NADH delivers more H+ and electrons into the ETS,
the proton gradient increases, with H+ building up
outside the inner mitochondrial membrane, and OH-inside
the membrane.

20. THANK YOU
Presentation by
R.Vijayarangan