This a power point presentation of Medical Biochemistry topic ETC.Which is also known as Oxidative Phosphorylation High yield points for PG entrance exam are also included in it.

1. (Respiratory chain)
JENIXUN I M
Velammal Medical College And
Research Institute Madurai.

2.  Mitochondrial inner membrane is impermeable to
NADH hence transport shuttles are used
1) Malate-Aspartate shuttle
2) Glycerol-3-Phosphate shuttle
Site of ETC : Inner mitochondrial membrane

3. Site: Liver and Heart

4. Site : Skeletal muscle and Brain

5. ETC has 4 protein complexes , 2 mobile electron carriers,
1 ATP synthesizing system
 Complex I : NADH Coenzyme Q Oxidoreductase
‒ Contain FMN and Fe-S (Iron- Sulfur) Complex
‒ Pumps 4 H+Q to Inter-membrane Space

6.  Complex II Succinate Q Reductase
‒ Contain FAD and FeS Complex
‒ No H+ pumped to Intermembrane Space
 Complex III Q Cytochrome c Oxidoreductase
‒ Contain Cyt b and Cyt c1
‒ Contain Fe-S Complex
-Pumps 4 H+Q to Intermembrane Space

7.  Complex IV Cytochrome c Oxidase
‒ Contain Cyt a and a3 and Copper A and Copper B centre
‒ 2H+ pumped to Intermembrane Space
 The final electron acceptor of ETC is oxygen( Has highest
redox potential)

8.  Coenzyme Q (Ubiquinone)
-Carrier between complex I and complex III
 Cytochrome C
-Carrier between complex III and complex IV

10.  Divided into two Sub complexes
 F0 Sub complex(Has proton channel)
 F1 Sub complex(Has ATP synthase enzyme)

11. The flow of electrons through the respiratory
chain generates ATP by the process of oxidative
phosphorylation (oxidation coupled with
phosphorylation)
 The proton motive force caused by the
electrochemical potential difference (negative
on the matrix side) drives the mechanism of
ATP synthesis.
AVAILABILITY OF ADP REGULATES ETC

12. Electron flow sequence of NADH
Complex I -> CoQ -> Complex III -> Cyt C -> Complex IV
Hence 10 protons are pumped out and 2.5 ATP is produced
Electron flow sequence of FADH2
Complex II -> CoQ -> Complex III -> Cyt C -> Complex IV
Hence 6 protons are pumped our and 1.5 ATP is produced as
complex II will not pump out any protons

13.  Divided into
• Inhibitors of Electron transfer
• Inhibitors of Oxidative Phosphorylation
• Uncouplers of Oxidative Phosphorylation
• Ionophores

14.  Inhibitors of Electron Transfer
 Between NADH and CoQ [At Complex I]
• An insecticide and a fish Poison Rotenone
• Amobarbital which is a barbiturate
 Inhibitor of Complex II
• TTFA (Tri enoyl TriFluoro Acetone) a Iron Chelating agent
• Carboxin
• Malonate, a competitive inhibitor of Succinate Dehydrogenase.
 Between Cyt b and Cyt c [At Complex III]
• Antimycin A
• British Antilevisite [Dimercaprol]
 Inhibitor at Cytochrome c Oxidase [Complex IV]
• CO
• Cyanide
• H2S

15.  Inhibitors of Oxidative Phosphorylation
 Atractyloside(By inhibiting the transporter of ADP into and
ATP out of the mitochondrion)
 Oligomycin an Antibiotic
(Completely blocks oxidation and phosphorylationby blocking
the flow of protons through F0 Complex of ATP Synthase)
 Uncoupler of Oxidative Phosphorylation
Mechanism of Action:Disruption of Proton Gradient
across the inner mitochondrial membrane
Eg: 2,4 Dinitrophenol

16.  Physiological Uncoupler
• Thermogenin (in Brown Adipose Tissue)
• Thyroxine
• Long Chain Free Fatty Acid
• Unconjugated Bilirubin.
 Ionophores
• Ionophores permit specific cations to penetrate membranes
• Dissipate Proton Gradient
Eg: Valinomycin
Gramicidin
Nigercin.

17.  REFERENCE
 Harper’s illustrated Biochemistry 31st edition
 Self assessment and review of Biochemistry by J.P. Rebecca
 Textbook of biochemistry by D.M. Vasudevan 9th edition