This document discusses biological oxidation and the electron transport chain (ETC). It begins by defining key concepts in bioenergetics like high energy compounds, substrate-level phosphorylation, and biological oxidation. It then describes the components and functioning of the ETC, including its role in generating ATP via oxidative phosphorylation. Specific enzymes and cofactors involved in biological oxidation reactions are examined, including dehydrogenases, oxygenases, oxidases, and hydroperoxidases. The roles of coenzymes like NAD+, FAD, and cytochromes in transferring electrons are also outlined.
2. Learning Objectives
Bioenergetics
High energy compounds
Substrate level phosphorylation
Biological Oxidation
ETC-Components and working
Uncouplers
Inhibitors and disorders of ETC
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Energy
Heat
energy
Chemical energy
Mechanical
energy
Electrical energy
10. High Energy Compounds Of Human Body
High energy compounds are energy rich compounds.
Possess high energy bonds in its structures.
Cleavage of these high energy bonds liberate more energy
than that of ATP hydrolysis.
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11. S.No Examples Of High Energy
Compounds
Free Energy
Released On
Hydrolysis.
Cal/mol
1 Phospho Enol Pyruvate -14.8
2 Carbamoyl Phosphate - 12.3
3 Cyclic AMP -12.0
4 1,3 Bis Phospho Glycerate -11.8
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12. S.No Examples Of High Energy
Compounds
Free Energy Released
On Hydrolysis.
Cal/mol
5 Creatine Phosphate -10.3
6 S Adenosine Methionine
( SAM)
-10.0
7 Succinyl CoA -7.7
8 Acetyl CoA -7.7
9 ATP -7.3
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13. Significance Of High Energy Compounds
Mode of generation of ATP at substrate level
Involves cleavage of high energy bond present in high
energy compound
Bond energy released is used for Phosphorylation reaction
Generates ATP directly and instantly at reaction level without
involvement of ETC
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14. Examples Of High Energy Compounds
Undergoing Substrate Level
Phosphorylation
S.No High
Energy
Compound
Enzyme
Catalyzing
Product
Obtained
High
energy
Phosphate
Compound
Generated
Metabolic
Pathway
Involved
1 1,3 Bis
Phospho
Glycerate
Phospho
Glycerate
Kinase
3 Phospho
Glycerate
ATP Glycolysis
2 Phospho
Enol
Pyruvate
Pyruvate
Kinase
Enol
Pyruvate
ATP Glycolysis
3 Succinyl
CoA
Succinate
Thio Kinase
Succinate GTP Krebs/TCA
Cycle
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15. During Anabolic pathways/reaction
High energy compounds follow condensation or bond
building reactions.
High energy compound cleave to generate energy
Energy used for building C-C bonds.
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16. High Energy Compounds Generated In
Catabolic Pathways Are Utilized In
Anabolic Reactions
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17. Important Features Of ATP
Contains three high energy phosphate bonds
Drive endergonic reactions
It is chemical energy currency of body
Functions in body as a complex with Mg2+
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18. Important Features Of ATP
Biosynthesized by ATP synthase
Couples thermodynamically Unfavorable reactions to
Favorable Ones
ATP synthesis is inhibited by Uncouplers
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19. What Is Biological Oxidation?
Biological Oxidation Reactions/Process
Involves Oxygen
Associated with metabolism
Generates ATP
Vital for functioning of cells
Survival and existence of human body.
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20. Oxidation reactions are biochemical reactions where there is
either:
Removal / Loss of Hydrogen (Dehydrogenation)
Removal or Loss of Electrons
Addition of Oxygen (Oxygenation)
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21. Oxidation of a molecule (electron donor) is always
accompanied by reduction of a second molecule
(electron acceptor)
Most predominant type of Oxidation reaction in body is:
Dehydrogenation Reaction- Catalyzed by
Dehydrogenases
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22. Dehydrogenases catalyzes to remove Hydrogen from
substrates.
Which are temporarily accepted by Coenzymes
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23. Coenzymes and Inorganic Cofactors Of
Biological Oxidation Reactions
FMN
FAD
NAD+
NADP+
THBP (Tetra Hydro Biopterin)
Cu++
Fe+++
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24. Oxidized Coenzymes involved in
Oxidation/Dehydrogenation reactions.
NAD+
NADP+
FAD
FMN
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25. Oxidized Coenzymes temporarily accept the hydrogen
from substrates and get transformed to reduced
coenzymes.
NADH+H+
FADH2
NADPH+H+
FMNH2
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26. 5 Enzymes of Biological Oxidation
Aerobic dehydrogenases
Anaerobic dehydrogenases
Oxygenases
Oxidases
Hydroperoxidases
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27. All 5 Enzymes of Biological Oxidation
reactions are classified in
Class I Oxido Reductases
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29. FMN are acceptors of removed Hydrogen
Reduced Coenzymes (FMNH2) formed are auto oxidizable
Reduced coenzymes get reoxidized at reaction level.
Oxygen gets directly involved at reaction level to reoxidize
the reduced coenzymes.
H2O2 is a byproduct of Aerobic Dehyrogenase activity.
Catalase then detoxify the H2O2 to H2O and O2
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30. Specific Examples Of
Aerobic Dehydrogenases
L Amino acid Oxidase
Xanthine Oxidase
Glucose Oxidase
Aldehyde Dehydrogenase
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31. ANAEROBIC DEHYDROGENASES
Anaerobic Dehydrogenases catalyzes to remove hydrogen
from substrates.
With the help of coenzymes NAD+/NADP+/FAD.
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32. Coenzymes temporarily accept the hydrogen from
substrates and get reduced to
NADH+ H+
FADH2
NADPH+H+
Reduced coenzymes formed in Anaerobic Dehydrogenase
reactions are : Non autoxidizable/not reoxidized at reaction
level.
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33. Reduced coenzymes NADH+H+ and FADH2 formed at
Anaerobic Dehydrogenase reaction
Has to enter ETC for its reoxidation.
Oxygen is involved indirectly at an end of ETC as electron
and proton acceptor .
Metabolic water is an end product of ETC
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34. DEHYDROGENASES CANNOT USE OXYGEN AS A
HYDROGEN ACCEPTOR
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35. Reduced coenzyme NADPH+H+ do not enter ETC
NADPH+H+ is utilized as reducing equivalent for reduction
reactions catalyzed by Reductases.
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37. NADP+ Dependent Dehydrogenases
Glucose -6-Phosphate Dehydrogenase
Phospho Gluconate Dehydrogenase
Note NADPH + H+ does not enter ETC for its reoxidation
instead they are involved in reduction reactions.
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39. FMN Dependent Anaerobic
Dehydrogenase
NADH Dehydrogenase (Warburg's Yellow Enzyme)
First Component of ETC/ Complex I of ETC
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40. OXYGENASES
Oxygenases add Oxygen atom from molecular oxygen (O2)
into substrate.
Form Oxidized Products
Oxygenases catalyze direct transfer and incorporation of
oxygen into a substrate molecule
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41. Mono Oxygenases
Mono Oxygenases add one oxygen atom from molecular
oxygen to the substrate.
Forms Hydroxyl group (-OH )
Monoxygenases are also termed as Hydroxylases or Mixed
Function Oxidase.
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42. Examples Of Mono Oxygenases
Phenylalanine Hydroxylase
Tryptophan Hydroxylase
25 Hydroxylase
1 α Hydroxylase
Cytochromes P450 Are Monooxygenases Important in
Steroid Metabolism & for Detoxification of Many Drugs
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43. Di Oxygenases
Dioxygenases are true Oxygenases
Incorporates two Oxygen atoms from O2
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44. Examples Of Dioxygenases
Tryptophan Di Oxygenase/ Tryptophan Pyrrolase
Homogentisate Oxidase
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45. Oxidases
Oxidases involve activated molecular Oxygen as Hydrogen
(electron and proton ) acceptor.
Oxidases Reduce Oxygen to form Water (H2O)
OXIDASES USE OXYGEN AS A HYDROGEN ACCEPTOR
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46. Examples Of Oxidases
Cytochrome Oxidase-Classic Example (Hemoprotein ETC
enzyme)
Ascorbate Oxidase
Mono Amine Oxidase
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47. Hydroperoxidases use hydrogen peroxide
or an organic peroxide as substrate
Hydroperoxidases detoxify Hydrogen Peroxide in body.
H2O2 is a substrate/reactant for Hydroperoxidases.
Hydroperoxidases are Hemoproteins.
Contains loosely bound Heme as prosthetic group.
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48. Hydroperoxidases prevent accumulation of H2O2 in cells.
H2O2 if accumulated in cells is toxic
Leads to disruption of membranes(Hemolysis).
Increases risk of cancer and atherosclerosis.
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49. Specific Examples Of Hydroperoxidases
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50. Peroxidases Reduce Peroxides Using
Various Electron Acceptors
Indirectly react with H2O2
Glutathione Peroxidase (In R.B.C’s)
Leukocyte Peroxidase (In W.B.C’s)
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52. Catalase
Directly reacts with H2O2.
Associated with Aerobic Dehydrogenase catalyzed reaction.
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53. What is ETC????
Truly Aerobic in nature (indispensable on O2)
Located and operated at - Inner membrane of Mitochondria
Accepts reducing equivalents from reduced coenzymes to
reoxidize
Transfer protons and electrons serially which are finally
accepted by activated molecular oxygen
Alternate Oxidation and Reduction Reactions carried out in
its process
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54. Oxidation process (ETC) is tightly coupled with
Phosphorylation of ADP with pi to generate ATP
Fate of ETC
Location of ETC components
Mature erythrocytes ????
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55. Components and Enzymes of
ETC are arranged towards inner
surface of inner membrane of
mitochondria as
Vectorial conformation
Increased order of positive
redox potential
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56. Role of mitochondrial DNA in ETC
Condition in which ETC/oxidative phosphorylation operates
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57. ETC Components
1.Flavo Protein- (First Component
of ETC)
NADH Dehydrogenase-FMN and
FeS centres (Warburg's Yellow
Enzyme)
2. Coenzyme Q / Ubiquinone
(Hydrophobic)
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58. 3. Series of Cytochromes-
(Haemoproteins)
Cytochrome b-Cytochrome c1-
Cytochrome c- Cytochrome aa3
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59. 4. Iron Sulphur Proteins
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60. Complexes OF ETC and oxidative
phosphorylation
Complex I- NADH CoQ Reductase NADH Dehydrogenase FMN and FeS
centre
Complex II – Succinate CoQ Reductase Succinate Dehydrogenase FAD and
FeS centre
Complex III–CoQ Cytochrome C Reductase Cytochrome b – Cytochrome c1
Complex IV- Cytochrome Oxidase Cytochrome aa3
Complex V – ATP Synthetase F0 and F1 of ATP Synthase
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61. NADH CoQ Reductase ETC Complex I
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62. Complex II – Succinate CoQ Reductase –
Succinate Dehydrogenase FAD and FeS centre
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63. Complex III–CoQ Cytochrome C Reductase
Cytochrome b – Cytochrome c1
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65. Complex IV- Cytochrome Oxidase
Cytochrome Aa3
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66. Complex I,III and IV Serves As Proton
Pumps To Generate Proton Gradient in
Intermembrane space
Complex I,III and IV serves as Proton Pumps
A proton gradient is created in intermembrane space
Complex I,III and IV serves as ATP generating sites
Complex I and III sites where 4 protons are pumped 1 ATP is
generated at each site
At Complex IV Site where 2 Protons are pumped 0.5 ATPs
are generated
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67. COMPLEX V- ATP SYNTHASE
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68. F1 contains 5 types of polypeptide
chains - α3β3γδε
Fo - a1b2c10-14
(c subunits form cylindrical,
membrane-bound base)
Fo and F1 are connected by a
γεstalk and by exterior column
(a1b2 and δ)
Proton channel is – between c ring
and a subunit.
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69. F0 is hydrophobic interspersed in inner membrane of
mitochondria composed of 10 C protein subunits
F0 serves as Proton channel, 4 protons from intermembrane
space move back to matrix through it
F1 is hydrophilic and projects into mitochondrial matrix
Gamma (bent axle) and F0- C subunit are rotatory , other all
are static subunits
Beta subunit is catalytic unit where ADP is phosphorylated
with pi to generate ATP
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74. Chemiosmotic Theory
Peter Mitchell
Oxidative process E.T.C and ATP synthesis are tightly
coupled by a proton gradient developed in an intermembrane
space of mitochondria.
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75. Regulation of ATP Synthesis
Intramitochondrial ratio ATP/ADP is a control mechanism
At high ATP/ADP ratio
ATP acts as an allosteric inhibitor for Complex IV
(Cytochrome Oxidase)
Inhibition is reversed by increasing ADP levels
Respiratory control or Acceptor control.
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76. Significance of ETC/oxidative
phosphorylation
Reduced coenzymes gets reoxidized to NAD+ /FAD in ETC
for its reutilization in metabolic oxidation reactions.
Oxidative phosphorylation generates chemical form of energy
ATP as a valuable by product
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77. Shuttle Systems
Malate-Aspartate Shuttle
Glycerol 3-phosphate Shuttle
Significance???
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82. Inhibitors Of ETC Complexes
Complex I
Amobarbital /Amytal-
Barbiturates
Rotenone (Fish/Rat Poison)
Piericidin A
Halothane
Complex II
Carboxin
TTFA (Thenoyl Trifluoro
Acetone)
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83. Complex III
Antimycin A
Naphthoquinone
Dimercaprol / British Anti
Lewisite ( BAL)
Complex IV
Carbon Monoxide
CN
Azide
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84. Inhibitors of Complex V
Oligomycin: Bind to Fo domain of ATP synthase
Atractyloside
Inhibit ATP-ADP translocase
Bongregate
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Active in Heart and Liver. 2.5 molecules of ATP are produced
Active in Skeletal muscles and Brain.FADH2 formed in this enter the electron-transport chain through CoQ
Generates only 1.5 molecules of ATP
ROTENONE AND PIERICIDIN A: Inhibits transfer of electrons from Fe-S centres in Complex I to Ubiquinone
Barbiturate-AmobarbitalBlocks NADH dehydrogenase and CoQ. Halothane inhibits both NADH:ubiquinone (Q) oxidoreductase and succinate dehydrogenase.
Carboxin block succinate dehydrogenase. TTFA doent allows electrons to pass to ubiquinone
Antimycin and BAL:It blocks the electron flow. Naphthoquinone : competitive inhibition of the active site of ubiquinone
CN: Blocks at cytochrome oxidase Binds with iron within this protein complex
CO: Binds with the reduced form of iron in the hem groups (Fe++) in Cytochrome Oxidase
Azide: Reacts with the ferric form (Fe3+) of the complex IV
(Oxidation) is uncoupled from Phosphorylation (ATP generation). Uncouplers deplete proton gradient of intermembrane space formed during ETC operation.
Uncouplers inhibit generation of ATP
Carry protons from intermembrane space across mitochondrial membrane to matrix From the site other than specific site.
changes the permeability of the mitochondrial membrane to protons.
Thermogenin is produced in brown adipose tissue of newborn mammals and hibernating mammals. This protein of the inner mitochondrial membrane functions as a H+carrier
Mitochondrial encephalomyopathy, lactic acidosis and stroke like episodes