The document summarizes the organization of the mitochondrial electron transport chain. It describes the five complexes of the electron transport chain (Complexes I-V), including their components, functions, and electron transfer processes. Specifically, it details how Complexes I, III, and IV transfer electrons from donors like NADH to final acceptors like oxygen. This generates a proton gradient across the inner mitochondrial membrane, which Complex V then uses to synthesize ATP through oxidative phosphorylation.

1. ORGANIZATION OF
MITOCHONDRIAL
ELECTRON
TRANSPORT CHAIN
SEMINAR REPRESENTED BY
QAMRUNNISA ABDUL WAHID SHAIKH
MSC-I (MICROBIOLOGY)
MB 603-CELLULAR METABOLISM

2. CONTENT
A.CELLULAR RESPIRATION
a.STEPS INCLUDE IN CELLULAR RESPIRATION
B.ELECTRON TRANSPORT CHAIN
a.MITOCHONDRIAL ELECTRON TRANSPORT CHAIN
b.COMPLEXES OF MITOCHONDRIAL ELECTRON TRANSPORT CHAIN
c.complexes of ETC
COMPLEX I : NADH:ubiquinone oxidoreductase
COMPLEX II: Succinate dehydrogenase
COMPLEX III: Ubiquinone:cytochrome c oxidoreductase
COMPLEX IV:Cytochrome oxidase
COMPLEX V : ATP synthase complex
C.SUMMARY
D.REFRENCES

3. Cellular respiration is a set of metabolic reactions and processes
that take place in the cells of organisms to convert biochemical
energy from nutrients to adenosine triphosphate (ATP) and then
release waste products.
Respiration is one of the key ways a cell releases chemical energy
to fuel cellular activity.
Nutrients that are commonly used by animal and plant cells in
respiration include sugar,amino acids and fatty acids, and the most
common oxidizing agent(electron acceptor) is molecular oxygen(O2).
The chemical energy stored in ATP and then be used to drive
processes requiring energy, including biosynthesis, locomotion or
transportation of molecules across cell membranes.
CELLULAR RESPIRATION:

4. STEPS INCLUDE IN CELLULAR
RESPIRATION:

6. ELECTRON TRANSPORT CHAIN:
An electron transport chain (ETC) is a series of complexes
that transfer electron from electron donor to electron
acceptor via redox (both reduction and oxidation occurring
simultaneously) reactions, and couples this electron transfer with
the transfer of protons (H+
ions) across a membrane. This creates
an electrochemical proton gradient that drives the synthesis
of adenosine triphosphate (ATP), a molecule that stores energy
chemically in the form of highly strained bonds.
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.

7. MITOCHONDRIAL ELECTRON TRANSPORT
CHAIN:
Most eukaryotic cells have mitochondria, which produce ATP from
products of the citric acid cycle, fatty acid oxidation, and amino acid
oxidation.
At the mitochondrial inner membrane, electrons from NADH
and FADH2 pass through the electron transport chain to oxygen,
which is reduced to water.
The electron transport chain comprises an enzymatic series of
electron donors and acceptors.
 Each electron donor will pass electrons to a more electronegative
acceptor, which in turn donates these electrons to another acceptor,
a process that continues down the series until electrons are passed to
oxygen, the most electronegative and terminal electron acceptor in
the chain.

8. Passage of electrons between donor and acceptor releases
energy, which is used to generate a proton gradient across the
mitochondrial membrane by actively pumping protons into the
intermembrane space, producing a thermodynamic state that has
the potential to do work.
The entire process is called oxidative phosphorylation, since ADP
is phosphorylated to ATP using the energy of hydrogen oxidation in
many steps.

9. NADH+H+
FMN
FeS
FeS
4H
+
NAD+
Q
4H
+
Succinate Fumarate
e-
Cyt c1
FeS
Cyt bL
Cyt bH
Cyt c
CuA
Cyt a
Cyt b3 CuB
½ O2+2H+
H2O
2H
+
Intermembrane
space
Inner
mitochondri
al membrane
Matrix

10. NADH:ubiquinone oxidoreductase or
NADH dehydrogenase
COMPLEX II: succinate dehydrogenase
ubiquinone:cytochrome c
oxidoreductase
COMPLEX III:
COMPLEX IV: cytochrome c oxidase
F1F0 ATP synthase complex: ATP
synthesis
COMPLEX V :
COMPLEXES OF MITOCHONDRIAL ELECTRON
TRANSPORT CHAIN:

11. COMPLEX I : NADH to Ubiquinone
NADH:ubiquinone oxidoreductase or NADH dehydrogenase
 It is a large enzyme complex , 850,000 Kd
 composed of 42 different polypeptide chains, including an FMN-
containing flavoprotein and at least six iron sulfur centers.
 Complex I is L-shaped, with one arm of the L in the membrane
and the other extending into the matrix.
NADH + 5H+
N +Q NAD+
+ QH2 +4H+
P

12. Complex I catalyzes two simultaneous and obligately coupled
processes:
(1) the exergonic transfer of a hydride ion to ubiquinone from
NADH and a proton from the matrix
(2) the endergonic transfer of four protons from the matrix to the
intermembrane space.
Amytal (a barbiturate drug), rotenone (a plant productcommonly
used as an insecticide), and piericidin A (an antibiotic) inhibit
electron flow from the Fe-S centers of Complex I to ubiquinone and
therefore block the overall process of oxidative phosphorylation.

13. COMPLEX II: Succinate to Ubiquinone
succinate dehydrogenase
It is the only membrane-bound enzyme in the citric acid cycle
It is an integral membrane protein.
it contains five prosthetic groups of two types and four different
protein subunits.
The enzyme contains three different iron-sulfur clusters and one
molecule of covalently bound FAD.
succinate is bound and a hydride is transferred to FAD to generate
FADH2 and fumarate. FADH2 then transfers its e- one at a time to the
Fe-S centers. finally transfer of 2 e-one at a time to coenzyme Q to
produce CoQH2.
No protons are translocated across the inner mitochondrial
membrane by complexII.
Succinate + CoQ Fumarate + CoQH2

14. Structure of Complex II
Two transmembrane subunits
C - green and D - blue
FAD – gold
Three sets of Fe-S centers - yellow
and red
Ubiquinone - yellow is bound to
subunit C and
heme b - purple is sandwiched
between subunits C and D.
A cardiolipin molecule is so tightly
bound to subunit C that it shows up in
the crystal structure - gray
spacefilling.
Electrons move -blue arrows
from succinate to FAD, then through
the three Fe-S centers to ubiquinone.

15. COMPLEX III: Ubiquinone to Cytochrome c
Cytochrome bc1 complex or ubiquinone:cytochrome c
oxidoreductase
Complex III has a beautiful dimeric
structure.
The bottom of the structure extends
75 Å into the mitochondrial matrix,
while the top of the structure extends
38 Å out into the intermembrane
space.
Myxothiazol, which prevents
electron flow from QH2 to the Rieske
iron-sulfur protein
Antimycin A, which blocks electron
flow from heme bH to Q
It passes the electrons form
CoQH2 to cyt c through a very unique
electron transport pathway called the
Q-cycle.

16. Q-CYCLE:

17. COMPLEX IV: Cytochrome c to O2
Cytochrome oxidase
Complex IV is a large enzyme (13 subunits; Mr 204,000) of the inner
mitochondrial membrane.
It contain two Cu ions complexed with the -SH groups of two Cys
residues in a binuclear center, two heme groups, designated a and a3,
and another copper ion (CuB).
Heme a3 and CuB form a second binuclear center that accepts
electrons from heme a and transfers them to O2 bound to heme a3.
Subunit I –has two heme groups, a and a3
copper ion CuB (green sphere).
Subunit II-contains two Cu ions complexed
with the -SH groups of two Cys residues in a
binuclear center.
Subunit III

18. Electron transfer through Complex IV is from cytochrome c to the CuA
center, to heme a, to the heme a3–CuB center, and finally to O2.
Path of electrons
through Complex IV
4 Cyt c (reduced) + 8H
+
N + O2 4 cyt c (oxidized) + 4H
+
P + 2H2O

19. COMPLEX V : F1F0 ATP synthase complex: ATP synthesis
The chemiosmotic model, proposed by
Peter Mitchell.
This enzyme complex embeded in inner
mitochondrial membrane. It synthesized ATP
in matrix, utilizing the energy of the proton
gradient (proton motive force) generated by
the ETC.
Synthesis of ATP in (F1) subunit. Proton
transport is coupled to ATP synthesis
About 4 H+ must move down the gradient for
each ATP produced
Free energy change for pumping one proton
is 20kJ/mol, thus for pumping 10 protons the
energy release is 200KJ/mol.
ATP formation requires 50KJ/mol of energy.
To emphasize this crucial role of the proton motive force, the equation
for ATP synthesis is sometimes written
ADP + Pi + nH+
P ATP + H2O +nH+
N

20. SUMMARY:

21. REFRENCES:
www.google.com
www.ncbi.nim.nih.gov.in
Lehninger- principles of biochemistry

22. THANK
YOU