Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st year (First Year) Biochemistry ppt lectures Topic 44 Final Biologcal Oxidation 18 Notes. - biochemistry notes pdf, biochemistry mbbs 1st year notes pdf, biochemistry mbbs notes pdf, biochemistry lecture notes, paramedical biochemistry notes, medical biochemistry pdf, biochemistry lecture notes 2022 ppt, biochemistry pdf.
Induction To Todays Topic
Any Guesses Of Todays Topic???
Energy Metabolism
Bioenergetics
BIOLOGICAL OXIDATION
Specific Learning Objectives
Questions Which Wil be Answered
What is system of Bioenergetics ?
How is chemical form of energy ATP formed (Generation)
and utilized (Operation) in human body ?
What Factors are associated to bioenergetics system?
Metabolites
Enzymes
Coenzymes
Cofactors
Hormones
Which disorders suffered due to defective system ?
Synopsis
vWhat is Bioenergetics?
vHigh Energy Compounds
vSubstrate Level Phosphorylation
vWhat is Biological Oxidation?
vEnzymes and Coenzymes of Biological
Oxidation Reactions
vElectron Transport Chain (ETC)
Continued---------
vOxidative Phosphorylation Mechanism
vInhibitors of ETC and Oxidative Phosphorylation
vUncouplers- Mode of Action
vShuttle System
vFactors Involved in Oxidative Phosphorylation
mechanism
Lets Get Introduced To
What Is Bioenergetics?
Bioenergetics or biochemical
thermodynamics is:
Study of energy changes during
biochemical reactions.
Biological Systems Conform to General
Laws of Thermodynamics
Energy Is Never Destructed
(Soul is energy never destructed and it is Immortal)
Total energy of a system, including its surroundings,
remains constant
Energy is neither lost nor gained during any change
May be transformed into another form of energy
May be transferred from one part of system to another
or
Conditions Of Bioenergetics
Isothermic (mostly)
Endothermic/
Endergonic/Anabolic
Exothermic/Exergonic
/Catabolic
ENDERGONIC ( Anabolic) PROCESSES
PROCEED BY COUPLING
OF EXERGONIC(Catabolic)
PROCESSES
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.
S.No
Examples Of High
Free Energy
Energy Compounds
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
S.No
Examples Of High Energy
Free Energy
Compounds
Released On
Hydrolysis.
Cal/mol
5
Creatine Phosphate
-10.3
6
S Adenosine Methionine
-10.0
( SAM)
7
Succinyl CoA
-7.7
8
Acetyl CoA
-7.7
9
ATP
-7.3
Significance Of High Energy
Compounds
OR
Fates Of High Energy Compound
In Catabolic And Anabolic
Pathways
During Catabolic pathways/reaction
High energy compounds follow
substrate level phosphorylation
reaction.
High energy compounds cleave high
energy bond to generate high energy
used for phosphorylation of ADP with
pi at reaction level.
Generate ATP at substrate/reaction
level.
Substrate Level Phosphorylation
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
Examples Of High Energy
Compounds Undergoing Substrate
Level Phosphorylation.
S.No
High Energy
Enzyme
Product
High
Metabolic
Compound
Catalyzing
Obtained
energy
Pathway
Phosphate
Involved
Compound
Generated
1
1,3 Bis
Phospho
3
ATP
Glycolysis
Phospho
Glycerate Phospho
Glycerate
Kinase
Glycerate
2
Phospho
Pyruvate
Enol
ATP
Glycolysis
Enol
Kinase
Pyruvate
Pyruvate
3
Succinyl
Succinate Succinate
GTP
Krebs/TCA
CoA
Thio
Cycle
Kinase
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.
HIGH-ENERGY PHOSPHATES
PLAY A CENTRAL ROLE IN ENERGY
CAPTURE AND TRANSFER
High Energy Compounds Generated In
Catabolic Pathways Are Utilized In
Anabolic Reactions
HIGH-ENERGY PHOSPHATES
ACT AS
"ENERGY CURRENCY" OF CELL
Free Energy of hydrolysis Of High
Energy Phosphate Bonds has
Important Bioenergetics
Significance
Adenylate Kinase (Myokinase)
Interconverts Adenine Nucleotides
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+
Biosynthesized by ATP synthase
Couples thermodynamically Unfavorable reactions to Favorable Ones
ATP synthesis is inhibited by Uncouplers
What Is Biological Oxidation?
Biological oxidations :
Oxidation
reactions/Process
Occurring in living
cells.
Importance/Features Of
Biological Oxidation
Biological Oxidation Reactions/Process :
Involves Oxygen
Associated with metabolism
Generates ATP
Vital for functioning of cells
Survival and existence of human
body.
Definition Of Oxidation Reactions
Oxidation reactions are
biochemical reactions where there is
either:
Removal / Loss of Hydrogen
(Dehydrogenation)
Removal or Loss of Electrons
Addition of Oxygen
(Oxygenation)
Feature Of Biological Oxidation
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
Dehydrogenases catalyzes
to remove Hydrogen from
substrates.
Which are temporarily
accepted by Coenzymes.
Coenzymes
and
Enzymes
of
Biological Oxidation
Reactions
Coenzymes
and
Inorganic Cofactors
Of
Biological Oxidation
Reactions
FMN
FAD
NAD+
NADP+
THBP (Tetra Hydro Biopterin)
Cu++
Fe+++
Oxidized Coenzymes involved in
Oxidation/Dehydrogenation
reactions.
NAD+
NADP+
FAD
FMN
Oxidized Coenzymes temporarily accept
the hydrogen from substrates and get
transformed to reduced coenzymes.
NADH+H+
FADH2
NADPH+H+
FMNH2
The reduced and oxidized forms of NAD
The reduced and oxidized forms of FAD
5 Enzymes of Biological Oxidation
1. AEROBIC
DEHYDROGENASES
2. ANAEROBIC
DEHYDROGENASES
3. OXYGENASES
4. OXIDASES
5. HYDROPEROXIDASES
All 5 Enzymes of
Biological Oxidation
reactions are classified
in
Class I
Oxido Reductases
AEROBIC DEHYDROGENASES
Aerobic Dehydrogenases are Flavoproteins
Enzymes covalently bound to coenzymes FMN or
FAD
MH2 Aerobic DH M
FMN FMNH2 (Auto
oxidizable)
Catalase
H2 +O2 H2O2 H2O + O2
FMN/FAD are acceptors
of removed Hydrogen
Reduced Coenzymes
(FMNH2/FADH2) 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.
Specific Examples Of
Aerobic Dehydrogenases
L Amino acid Oxidase
(Oxidative Deamination of A.A)
Xanthine Oxidase
(Purine Catabolism)
Glucose Oxidase
(Glucose Oxidation to Gluconic acid)
Aldehyde Dehydrogenase
( Alcohol Metabolism)
ANAEROBIC DEHYDROGENASES
Anaerobic Dehydrogenases
catalyzes to remove
hydrogen from substrates.
With the help of coenzymes
NAD+/NADP+/FAD.
DEHYDROGENASES CANNOT
USE OXYGEN AS A HYDROGEN
ACCEPTOR
MXH2 Anaerobic Dehydrogenase MX
NAD+ NADH+ H+ (Non auto oxidizable)
Enter Electron Transport Chain
For its reoxidation
Coenzymes temporarily accept the
hydrogen from substrates and get
reduced to
NADH+ H+
FADH2
NADPH+H+
FMNH2
Reduced coenzymes formed in
Anaerobic Dehydrogenase
reactions are :
Non autoxidizable/not reoxidized
at reaction level.
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.
Remember
Reduced coenzyme NADPH+H+
do not enter ETC
NADPH+H+ is utilized as
reducing equivalent for
reduction reactions catalyzed
by Reductases.
NAD+ Dependent Anaerobic Dehydrogenases
Enzymes
Pathway /Reaction
Glyceraldehyde -3-PO4
Glycolysis
Dehydrogenase
Pyruvate Dehydrogenase
PDH Complex
Isocitrate Dehydrogenase
TCA cycle
Ketoglutarate Dehydrogenase
TCA cycle
Malate Dehydrogenase
TCA cycle
Lactate Dehydrogenase
Pyruvate/Lactate metabolism
Glutamate Dehydrogenase
Glutamate metabolism
Hydroxy Acyl Dehydrogenase
Beta Oxidation of Fatty acids
NADP+ Dependent
Dehydrogenases
Glucose -6-Phosphate Dehydrogenase
( HMP Shunt)
Phospho Gluconate Dehydrogenase
(HMP Shunt)
Note NADPH+H+does not enter ETC for
its reoxidation instead they are involved in
reduction reactions.
FAD Dependent Anaerobic
Dehydrogenases
Succinate Dehydrogenase
(TCA Cycle)
Acyl CoA Dehydrogenase
( Oxidation Of Fatty Acids)
FMN Dependent Anaerobic
Dehydrogenase
NADH Dehydrogenase
(Warburg's Yellow
Enzyme)
First Component of ETC/
Complex I of ETC
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
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.
AH + O2+BH2 Mono Oxygenase AOH+ B+H2O
Tyrosine+O2+THBP Tyrosine
DOPA+DHBP+H2O
Hydroxylase
Examples Of Mono Oxygenases
Phenylalanine Hydroxylase
(Phenylalanine to Tyrosine)
Tryptophan Hydroxylase
(Tryptophan to 5HydroxyTryptophan)
25 Hydroxylase
(Vitamin D - Cholecalciferol activation)
1 Hydroxylase
(Vitamin D - Cholecalciferol activation)
Di Oxygenases
Dioxygenases are true Oxygenases
Incorporates two Oxygen atoms
from O2.
A+ O2 Dioxygenase AO2
Examples Of Dioxygenases
Tryptophan Di Oxygenase/
Tryptophan Pyrrolase
(Tryptophan NFormyl Kynurenine )
PHPP Dioxygenase
Cysteine Dioxygenase
Homogentisate Oxidase
(Homogentisate to 4 Maleyl Acetoacetate)
Cytochromes P450
Are Monooxygenases
Important in Steroid Metabolism
& for
Detoxification of Many Drugs
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
AH2 + ? O2 Oxidase A+ H2O
Tyrosine+ O2 Tyrosinase -Cu++ DOPA +
H2O
Examples Of Oxidases
Cytochrome Oxidase-Classic Example
(Hemoprotein ETC enzyme)
Ascorbate Oxidase
Mono Amine Oxidase
Catechol Oxidase
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.
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.
Specific Examples Of
Hydroperoxidases
Peroxidases
Catalase
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)
H2O2 + 2 GSH Glutathione Peroxidase 2H2O + GSSG
(Reduced (Oxidized
active Form)
inactive Form)
Catalase
Directly reacts with H2O2.
Associated with Aerobic
Dehydrogenase catalyzed
reaction.
2H2O2 Catalase 2H2O +O2
Biological Oxidation Process
Electron Transport Chain
(ETC)
Oxidative Phosphorylation
Synonyms Of ETC
1. Electron Transport Chain (ETC)
2. Oxidative Phosphorylation
3. Electron Transport System (ETS)
4. Fate of Reduced Coenzymes of
FADH2 and NADH+H+
5. Respiratory Chain
6. Internal/Cellular Respiration
7. Tertiary metabolism
8. Final Oxidative Pathway
What is Electron Transport Chain?
Electron Transport chain
Biological oxidation process very vital for human
being survival
Truly Aerobic in nature(indispensable on O2)
Located and operated at inner membrane of
Mitochondria
Alternate Oxidation and Reduction Reactions
carried out in process
What is Oxidative Phosphorylation?
Oxidation process (ETC) is tightly
coupled with Phosphorylation of
ADP with pi to generate ATP.
Illustrated as Sun and Day Light
Oxidative
Phosphorylation is a
major mode of ATP
generation in
human body
What is Fate of ETC/
Oxidative Phosphorylation ?
REOXIDIZES
REDUCING EQUIVALENTS
(NADH+ H+ and FADH2)
GENERATED DURING ANAEROBIC
DEHYDROGENASE REACTION
Electron Transport Chain
On Operation
Transports Electrons and Protons
Through series of ETC components
Finally H2 is received by activated
molecular Oxygen (1/2 O2)
Generates significant byproduct ATP
and metabolic water at end of process
Condition In which ETC Operates
ETC operates in truly aerobic
condition.
Oxygen unloaded at cellular
level by HbO2
Gets utilized at an end of ETC
process. (Respiratory Chain)
Site Of
Electron Transport Chain
OR
Oxidative Phosphorylation
ETC is located and operated
in all cells which contain
Mitochondria (Power house
of Cell)
(Except mature Erythrocytes which are
devoid of mitochondria)
Location of Mitochondrial ETC Complexes
? Inner membrane of Mitochondria
? Rich In Cardiolipin
Components and Enzymes of ETC
are arranged towards inner
surface of inner membrane of
mitochondria as:
Vectorial conformation
Increased order of positive redox
potential
Number of Mitochondria Vary in
Different cells
Number of Mitochondria changes
from cell to cell , tissue to tissue,
organ to organ, organism to
organism
Factors Responsible For Number of
Mitochondria in Cell
Type of cell, organ and its
function
Metabolic status of an individual
Physical activity of an individual
How much energy cell needs to
produce?
High number of Mitochondria present in
Heart, Rod cells, Sperm,
ciliated cells
Muscle cells for example, contain more
number of mitochondria compared to
Kidney cells.
Marathon runners have more number of
mitochondria in their leg muscle cells than
people with desk jobs
Components Of ETC
Series Of Protein Complexes
Flavoproteins & Iron-Sulfur
Proteins (Fe-S),Cytochromes
are Components
of Respiratory Chain Complexes
1.Flavo Protein- (First Component)
NADH Dehydrogenase-FMN and FeS
centers(Warburg's Yellow Enzyme)
2. Coenzyme Q/ Ubiquinone
3. Series of Cytochromes-
Cytochrome b-Cytochrome c1-
Cytochrome c- Cytochrome aa3
Coenzyme Q / Ubiquinone
Coenzyme Q (CoQ)/ Ubiquinone)
is located in lipid core of
mitochondrial membrane.
It is a Quinone derivative
Lipophilic dissolves in
hydrocarbon core of a membrane.
Coenzyme Q is very
hydrophobic.
Coenzyme Q has a long Poly
isoprenoid tail, with multiple
units of isoprene.
In human cells, most often n = 10
Q10 isoprenoid tail is longer than
width of a bilayer.
Coenzyme Q functions as a
mobile e- carrier within
mitochondrial inner
membrane.
Its role in trans-membrane H+
transport coupled to e-
transfer (Q Cycle).
Coenzyme Q
Accepts
Both Protons and Electrons
Quinone ring of
coenzyme Q can
be reduced to
Quinol in a 2e-
reaction:
Q + 2 e- + 2 H+ QH .
2
When bound to special sites in respiratory complexes,
CoQ can accept 1 e- to form a semiquinone radical (Q?
-).
Thus CoQ, like FMN, can mediate between 1 e- & 2 e-
donors/acceptors.
Cytochromes
Cytochromes are Hemoproteins
conjugated proteins in ETC
Carrier of electrons
Contain heme as prosthetic group
Cytochrome Heme
Cytochrome Heme Iron is in
transitional state
Carries only electrons
Fe (III) + e- Fe (II)
Only one electron is transferred at
a time.
Cytochrome heme iron
can undergo 1 e-
transition between ferric
and ferrous states:
Fe+++ + e- Fe++
(oxidized) (reduced)
Cytochromes May Also Be
Regarded as Dehydrogenases
Series of Cytochromes b, c , c, aa
1
3
relay electrons (one at a time, in this
order
Cytochrome c is a small,
water soluble protein with a
single heme group.
Cytochromes a & a3 are
often referred to as
Cytochrome Oxidase
/complex IV
Cytochrome aa3 has Fe and
Cu.
All Cytochromes
except Cytochrome
Oxidase are Anaerobic
Dehydrogenase
activity.
Cytochromes absorb light at
characteristic wavelengths.
Absorbance changes upon
oxidation/reduction of
Heme Iron
Components of Respiratory Chain
are Contained in
Protein Complexes Embedded in
Inner Mitochondrial Membrane
Five Complexes of
Oxidative Phosphorylation
Complexes of Oxidative
Phosphorylation
There exists 5 complexes
Processing Oxidative
Phosphorylation to generate
ATP
Complexes are combination of one
or two components
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
Composition of Oxidative Phosphorylation Complexes
No. of
Prosthetic Groups
Complex
Name
Proteins
Complex I
NADH ?CoQ
46
FMN,
Reductase
9 Fe-S centers
Complex II
Succinate-CoQ
5
FAD, cyt b ,
560
Reductase
3 Fe-S centrs.
Complex III
CoQ-cyt c Reductase
11
cyt b , cyt b , cyt c ,
H
L
1
Fe-SRieske
Complex IV
Cytochrome Oxidase
13
cyt a, cyt a , Cu , Cu
3
A
B
ETC Components Associated With
Multiple Iron Sulfur Centers
Iron exists in Transitional State
Responsible for Oxidation and
Reduction Reactions
Complex I,I and II contains Iron
Sulfur Centers
Complex IV and V do not Contain
Iron Sulfur Centers
ETC Components
With Iron Sulfur Centers
NADH Dehydrogenase
Coenzyme Q-Cytochrome Reductase
Succinate ?Coenzyme Q Reductase
Iron-sulfur centers (Fe-S) are prosthetic groups
containing 2, 3 , 4 or 8 iron atoms complexed to elemental
& Cysteine S.
4-Fe centers have a tetrahedral structure, with Fe & S
atoms alternating as vertices of a cube.
Cysteine residues provide S ligands to the iron, while also
holding these prosthetic groups in place within the protein.
Electron transfer proteins
may contain multiple Fe-S
centers.
Iron-sulfur centers
transfer only one
electron, even if they
contain two or more iron
atoms, because of close
proximity of iron atoms.
Fe+++ (oxidized) + 1 e- Fe++ (reduced)
COMPLEX IV
Cytochrome a-a3/ Cytochrome Oxidase
large protein
Both a and a3 contain heme and Cu
Does not contain Fe ?S clusters
a3 Cu binds to oxygen and donates
electrons to oxygen
Cytochrome a3 - only component of
ETC that can interact with O2
Cytochrome Oxidase (complex IV) carries out
following irreversible reaction:
O + 4
O
2
H+ + 4 e- 2 H2
Four electrons are transferred into complex one at
a time from Cytochrome c.
Complex IV/Cytochrome
Oxidase reduces molecular
Oxygen to water.
Cytochrome Oxidase
Cu(II) Cu(I)
e- from cyt c to a
Heme A and Cu act together to
transfer electrons to oxygen
Metal centers of cytochrome oxidase (complex IV):
heme a & heme a3,
CuA (2 adjacent Cu atoms) & CuB.
O2 reacts at a binuclear center consisting of heme
a and Cu .
3
B
An Iron-Copper Center
in Cytochrome Oxidase
Catalyzes Efficient O2
Reduction
Complex V
ATP Synthase
Two units, Fo and F1
("knob-and-stalk"; "bal on a stick")
F1 contains the catalytic subunits
where ADP and Pi are brought
together for combination.
F0 spans the membrane and serves as
a proton channel.
? F1 contains 5 types of
polypeptide chains - a3b3gde
? Fo - a1b2c10-14
(c subunits form cylindrical,
membrane-bound base)
? Fo and F1 are connected by a
ge stalk and by exterior
column (a1b2 and d)
? Proton channel is ? between c
ring and a subunit.
Complex V ATP Synthase
How do ATPase and ATP Synthase
Differ?
ATPase is an enzyme that
hydrolyze ATP to form ADP
ATP synthase synthesize ATP
Both enzyme found in mitochondria
F- ATPase/ATP Synthase
F-ATPase belong to
superfamily of related ATP
Synthases
F-ATPase is a Rotating Motor
Mechanism Of Oxidative
Phosphorylation
Salient Features/Required Criteria's
Of
ETC/Oxidative Phosphorylation
OR
Criteria's Required For Oxidative
Phosphorylation
1
Arrangement Of
Electron Transport Chain
Components In Increased Order
Of Positive Redox Potential
Redox Potentials & Redox Couples
FREE ENERGY
CHANGES CAN BE
EXPRESSED IN TERMS
OF REDOX POTENTIAL
Redox Potential is a
measure of tendency of a
redox couple to accept or
donate electrons under
standard condition.
Components that have most negative
redox potentials
Have weakest affinity for electrons
Hence has capacity to donate its
electrons.
Redox couple with most positive
redox potentials have
Strongest affinity for electrons
therefore
Possess strongest tendency to
accept electrons.
During E.T.C there is transfer
of reducing equivalents
From low redox potential
to high redox potential.
This exhibit free energy
change there by liberating
heat energy
Electrons move spontaneously from
one component of ETC to another
with a
low redox potential (a low affinity
for electrons) to a component with a
high redox potential (a high
affinity for electrons)
In ETC electrons move from a
carrier with
Low redox potential
(high tendency to donate
electrons) toward carriers
Higher redox potential
(high tendency to accept
electrons)
Redox Couple
Components of ETC has capacity
to exist in oxidant and reduced
forms.
This pair is known as redox
couple
CoQ/CoQH2
Cyt b Fe+++/Cyt b Fe++
Sequence of
Respiratory
Electron
Carriers
Inhibitors
in green
2
Development Of
Proton Gradient And Proton Motive Force
In Intermembrane Space
Complex I,I I and IV
Pumps Protons From Matrix side
to Intermembrane Space
and generates
Proton Motive Force
Complex I,I I and IV
Serve as Proton Channels
Complex I ,III and IV act as a
Proton Pump.
Pump out protons from matrix
side to inter membrane space of
mitochondria.
Develop a proton gradient in
inter membrane space.
This supports the mechanism of
Oxidative Phosphorylation.
A Large Drop in Redox
Potential across each of the
three Respiratory Enzyme
Complexes (I,III,IV).
Provides the Energy for H+
Pumping
3
Free Energy Change Occurs
Due To Transport OF Proton
Pumping and Electron Exchange
During Oxidative Phosphorylation
4
Heat Energy Generated At Certain
Specific Sites During Oxidation
Is Transformed By Chemical
Phosphorylation Reaction of ADP
and pi to form ATP
5
ATP Synthase /Complex V
Activation for Phosphorylation
Reaction
Proton gradient runs
downhill through ATP
Synthase to drive
synthesis of ATP
qF F of ATP Synthase catalyzes
1 o
phosphorylation reaction for ATP
synthesis
q Transport of H+ from intermembrane
space to into the mitochondrial matrix
through ATP Synthase is mandatory.
qTransport of at least 3 H+ per ATP is
required through ATP Synthase for its
activation and catalysis.
Thus heat energy is
transformed to
chemical form of
energy (ATP) in
Oxidative
Phosphorylation.
6
Oxygen is Terminal Acceptor of
Protons and electrons During
Oxidative Phosphorylation To
Generate Metabolic Water
Oxygen has highest (most
positive) standard redox
potential
Most likely to accept electrons
from other carriers.
Electrons ultimately reduce Oxygen
to water (metabolic water)
2 H+ + 2 e- + ? O2 -- H2O
At end of E.T.C by catalytic activity of
Cytochrome Oxidase
Protons released at Coenzyme Q and
electrons transported by Cytochromes
are
Accepted by activated molecular
oxygen (1/2 O2) to form metabolic
water.
Cytochrome oxidase
controls rate of O2
uptake which
Means this enzyme
determines how
rapidly we breathe.
Respired Oxygen
transported by Hb
unloaded at tissue/
cellular level is
utilized during E.T.C.
7
Coenzyme Q Accepts Electrons
Via Complexes I & II
Point To Note
In ETC electrons flow from
Most electro negative potential
NADH+H+ (-0.32) to most
electro positive potential
(+0.82) ? O2 .
HOW
ETC /Oxidative
Phosphorylation Operates ?
Most Oxidative
Metabolic Pathways
(TCA and Beta Oxidation Of Fatty acids)
Located In Mitochondrial Matrix
Generate Reduced Coenzymes
Reduced coenzymes
NADH+H+/FADH2
Generated during Anaerobic
Dehydrogenase reactions of
Carbohydrates, Lipids metabolic
pathways.
Get reoxidized on entering E.T.C
Reduced coenzymes NADH+H+ and
FADH2 are formed in Mitochondrial
matrix:
Oxidative Decarboxylation of
Pyruvate to Acetyl CoA by PDH
complex.
Oxidation of Acetyl CoA by TCA cycle
Beta Oxidation of fatty acids
NADH+H+ and FADH2 are
energy rich molecules
Contains a pair of
electrons having a high
transfer potential.
Entry Of NADH+H+ in ETC
When NADH+H+ enters ETC reducing
equivalents Protons and Electrons are
taken up by first component
/Complex I (Flavoproteins)
Then from complex I the reducing
equivalents are transferred to CoQ.
Entry Of FADH2 in ETC
FADH2 is generated at Succinate
Dehydrogenase reaction(Complex II)
FADH2 enters ETC process and its
reducing equivalents are taken up by
CoQ .
CoQH2 then here onwards transfers
only electrons to series of arranged
Cytochromes and Protons are
released in matrix.
ELECTRON TRANSPORT CHAIN
Series of enzyme complexes (electron carriers)
embedded in the inner mitochondrial membrane, which
oxidize NADH+H+ and FADH2 and transport electrons to
oxygen is cal ed Respiratory Electron-Transport Chain
(ETC).
Sequence of Electron Carriers in ETC
NADH FMN-Fe-S Co-Q Fe cyt b
cyt c1 cyt c cyt a cyt a3 O2
Succinate FAD Fe
-S
Electrons of NADH or FADH2 are used to
reduce molecular oxygen to water.
A large amount of free energy is liberated.
The electrons from NADH+H+ and FADH2 are not
transported directly to O2 but are transferred
through series of electron carriers that undergo
reversible reduction and oxidation.
ETC Process
A PROTON GRADIENT POWERS THE
SYNTHESIS OF ATP
Transport of electrons from NADH or FADH2 to O2 via the
electron-transport chain is exergonic process:
NADH + ?O2 + H+ H2O + NAD+
FADH2 + ?O2 H2O + FAD+
Go' = -52.6 kcal/mol for NADH
-36.3 kcal/mol for FADH2
This process is coupled to the synthesis of ATP (endergonic
process)
ADP + Pi ATP + H2O Go'=+7.3 kcal/mol
In E.T.C both Protons and Electrons
are transferred up to Coenzyme Q
level.
At coenzyme Q level protons (2H+)are
released in the medium.
From Coenzyme Q onwards only
electrons are transferred through a
series of Cytochromes in E.T.C.
Electrons get transfer through
series of Cytochromes
Cytochrome Fe is in transitional
state (Ferric/Ferrous ).
In E.T.C there are
alternate reduction
and oxidation
reactions.
Flow of electrons through ETC
complexes leads to pumping of
protons out of the mitochondrial
matrix in intermembrane space.
This accumulation of protons
generates a pH/Proton gradient
and a transmembrane electrical
potential that creates a proton
motive force.
A Large Drop in Redox
Potential across each of the
three Respiratory Enzyme
Complexes (I,III,IV).
Provides the Energy for H+
Pumping
Electron Transport (Oxidative
Process) is coupled to Phosphorylation
ATP is synthesized when 3
protons flow back from
intermembrane space of
mitochondria to
mitochondrial matrix through
an enzyme complex ATP
synthase.
Oxidation of fuels and
phosphorylation of ADP
are coupled by a proton
gradient across an inner
mitochondrial membrane.
Thus Oxidative phosphorylation
is process in which ATP is
formed
As a result of transfer of
electrons from NADH or
FADH2 to O2 by a series of
electron carriers.
Mechanism
Of
Oxidative Phosphorylation
Oxidative Phosphorylation
Oxidation tightly coupled
with Phosphorylation
E.T.C (Oxidation)Process
coupled with phosphorylation
of ADP+pi to generate ATP.
Hypothesis And Theories Mechanism
Of
Oxidative Phosphorylation
Chemical Coupling Hypothesis
Conformational Coupling Hypothesis
Chemiosmotic Theory
Chemical Coupling Hypothesis:
Put forward by Edward Slater (1953)
Proposed series of high energy
phosphorylated intermediates are
produced during E.T.C operation.
Which are used to produce ATP.
Conformational Coupling
Hypothesis
Paul Boyer 1964
Mitochondrial Cristae undergo
conformational change in the
components of E.T.C.
E.T.C components attain high
energy state which are responsible
for the ATP production.
Chemiosmotic Theory
Put forward by Peter Mitchell (1961)
(Nobel Prize, 1978)
E.T.C process and ATP synthesis is
coupled by a proton gradient
developed in intermembrane space of
mitochondria.
Mitchell's Postulates for
Chemiosmotic Theory
Intact inner mitochondrial
membrane is required
Electrons are pumped through ETC
complexes I,III and IV.
Generates a Proton gradient and
in intermembrane space of
mitochondria.
Proton pumps are Complexes I,
III and IV.
Protons return through ATP synthase
Oxidative Phosphorylation
Proton gradient in inter
membrane space creates Proton
Motive Force due to:
Proton gradient have a
thermodynamic tendency
Proton gradient creates
Electrochemical potential
difference
Proton Motive Force drives the
Protons from mitochondrial
intermembrane space back to
matrix side
Through a specific site of F0 and
F1 particle of ATP Synthase.
ATP Synthase catalyzes the
phosphorylation of ADP with pi
In a reaction driven by movement
of H+ across the inner membrane
back into the matrix through it.
Translocation of protons through
ATP Synthase
Stimulates and activates ATP
Synthase
For catalytic action of
phosphorylation- ADP with pi to
form ATP.
Supports mechanism of Oxidative
Phosphorylation.
Flow of three H+ through an ATP
Synthase complex
Brings a conformational change n
domains of ATP Synthase
Which causes the ATP synthase
activate and catalyze
phosphorylation reaction
To synthesize ATP from ADP + Pi.
ATP Synthase, a Molecular Mill.
ATP synthesis at F1 results from
repetitive conformational changes
as rotates
rotates 1/3 turn-
energy for ATP release
This process of producing ATP
is known as oxidative
phosphorylation.
Entire process of using Proton
gradient and proton motive
force to make ATP is called
Chemiosmosis.
During oxidative
phosphorylation total energy
change is released in small
increments.
So that energy can be trapped as
chemical bond energy and form
ATP.
Coupling of ATP synthesis to
respiration is indirect, via a H+
electrochemical gradient.
Overview of Oxidative Phosphorylation
+
+
+
+ +
+
-
-
-
-
As electrons flow through complexes of ETC, protons are translocated
from matrix into the intermembrane space.
The free energy stored in the proton concentration gradient is tapped
as protons reenter the matrix via ATP synthase.
As result ATP is formed from ADP and Pi.
ATP Translocation From
Mitochondria
Through ATP/ADP Translocases
ATP molecules produced in Oxidative
Phosphorylation mechanism are
Transported out of mitochondrial
matrix through specific transporters
Operation Of ETC
Glycolysis, Fatty
acid oxidation
TCA cycle
supplies NADH
and FADH2 to
the Electron
Fatty Acids
Acetyl Co A
Transport Chain
Pyruvate
Amino Acids
Glucose
WHY ETC OPERATES ?
During E.T.C operation total
energy change is released in
small increments
So that energy can be trapped
as chemical bond energy to
form ATP.
When two redox couples of ETC
differ from each other by 0.22 volts
in standard redox potential.
At this site free energy in the form of
heat released which is more than 7.3
Kcal.
This free heat energy is conserved to
undergo Phosphorylation reaction
and generate chemical form of
energy-ATP.
Sites in E.T.C at which
energy liberated is less
than 7.3 Kcal is simply
dissipiated in the
form of heat.
Three sites in E.T.C (Complex
I,III and IV) where heat energy
liberated more than 7.3 Kcal
Utilized for phosphorylation
reaction of ADP with pi to
form ATP.
Electrons are transferred from
NADH+H+ O via multisubunit
2
inner membrane complexes I, III
& IV, plus CoQ & Cytochrome c.
Within each complex, electrons
pass sequentially through a series
of electron carriers.
Complex I catalyzes
oxidation of NADH+H+ with
reduction of coenzyme Q:
NADH + H+ + FP NAD+ + FPH2
Coenzyme Q accepts 2 e- and picks
up 2 H+ from FPH2 to yield the fully
reduced QH2.
Succinate Dehydrogenase of the Krebs Cycle is
also called complex II or Succinate-CoQ
Reductase.
FAD is initial e- acceptor.
FAD is reduced to FADH2 during oxidation of
Succinate to Fumarate.
FADH2 generated by Succinate
Dehydrogenase reaction gets reoxidized
by transfer of electrons through a series
of 3 iron-sulfur centers to CoQ, yielding
CoQH2.
QH2 product may be reoxidized via
complex III.
Providing a pathway for transfer of
electrons from Succinate into respiratory
chain.
Complex III/ Cytochrome b-c1
complex accepts electrons from
coenzyme QH2 that is generated
by electron transfer in complexes
I & II.
Cytochrome c resides in
intermembrane space.
It alternately binds to
complex III or IV during e-
transfer.
Significance Of ETC
Reduced coenzymes gets reoxidized
to NAD+ /FAD in ETC for its
reutilization in metabolic oxidation
reactions.
Reduced coenzymes NADH+
H+/FADH2 give its reducing
equivalents to E.T.C components and
get reoxidized.
E.T.C generates chemical form of
energy ATP as a valuable by product.
P/O Ratio
Ratio of ATPs formed per
Oxygen reduced
OR
Number of ATPs generated
per Oxygen atom used in
ETC process.
To make 1 ATP need 30 kJ/mole
There needs more than one
proton to translocate during
ETC process to generate 1 ATP.
Ten protons are pumped out of
the matrix during the two electrons
flowing from NADH+H+ to O2
(Complex I, III and IV).
Six protons are pumped out of the
matrix during the two electrons
flowing from FADH2 to O2
(Complex III and IV).
Spontaneous electron flow
through each of complexes I, III, &
IV is coupled to H+ ejection from
matrix to intermembrane Space
A total of 10 H+ are ejected from the mitochondrial matrix per 2 e
- transferred from NADH to oxygen via the respiratory chain.
A total of 6 H+ are ejected from the mitochondrial matrix per 2 e-
transferred from FADH2 to oxygen via the respiratory chain.
Complex I and Complex III transports 4H+
out of the mitochondrial matrix per 2e-
transferred from NADH.
Thus there are 2H+ per 2e- that are
effectively transported by complex
IV.
ATP Yield
3
4
4
2
10 protons translocates
per NADH+H+
6 protons translocates
per FADH2
Proton gradient and Proton
motive Force created as
electrons transferred to
Oxygen forming water
10 H+ / NADH+H+
6 H+ / FADH2
F F couples ATP synthesis to H+
1 o
transport into the mitochondrial matrix.
Transport of least 3 H+ per ATP is
required.
Translocation of 3H+
required by ATP Synthase for
each ATP produced
1 H+ needed for transport of Pi.
Net: 4 H+ transported for
each ATP synthesized
through ATP Synthase.
P:O Ratio for NADH+H+
10 H+ X 1 ATP = 2.5 ATP
4 H+
P.O Ratio for FADH2
6 H+ X 1 ATP = 1.5 ATP
4 H+
P:O ratio for NADH: 10 H+/4H+ =
2.5 ATP
P:O ratio for FADH2: 6 H+/ 4H+ =
1.5 ATP
ATP Is A Valuable Byproduct Of
Oxidative Phosphorylation
ATP is a high energy phosphate
compound
Biologically important free
nucleotide
ATP has Two High Energy Phosphate
Anhydride Bonds
ATP is energy currency of
cell.
Predominantly generated
through Oxidative
Phosphorylation.
Sites Of ATP Production In ETC
3 sites Of ATP Generation in ETC
Site I/Complex I-
Electrons transferred from Complex I to
CoQ
Site II/Complex III-
Electrons transferred from Cyt b to Cyt c1.
Site III/Complex IV-
Electrons transferred from Cytochrome
aa3/Complex IV/Cytochrome Oxidase to ?
O2
Thus ATP Generation
Is Due To Transformation Of
Heat Energy Into Chemical Form Of Bond Energy
Which Satisfy Law Of Thermodynamics
Energy Is never Destructed
Energy Is Transformed From One Form To Another
From One System To Another
One Body To Another
Significance OF ATP
ATP allows coupling of
thermodynamically
unfavorable reactions
to favorable reactions.
Uses of ATP generated in
Oxidative Phosphorylation
?Synthetic/Anabolic reactions
?Active transport mechanism.
?Muscular contraction
?Nerve impulse conduction.
ATP is continually being
hydrolyzed and
regenerated
A person at rest
consumes and regenerate
3 ATP/ sec
Staying Alive Energy Wise
We need 2000 Cal/day or 8,360 kJ of energy per day
Each ATP gives 30.5 kJ/mole of energy on hydrolysis
We need 246 moles of ATP
Body has less than 0.1 moles of ATP at any one time
We need to make 245.9 moles of ATP
Each mole of Glucose yields 38 ATPs or 1160 kJ
We need 7.2 moles of Glucose (1.3 kg or 2.86 pounds)
Each mole of Stearic acid yields 147 ATPs or 4,484 kJ
We need 1.86 moles of stearic acid (0.48 kg or 1.0
pound of fat)
Remember
CoQ accepts electrons and
Protons by complexes I and II
Acceptance of Protons and
Electrons from Complex II by
CoQ does not generate ATP
E.T.C is a Mode For Free Radical
Generation
During E.T.C operation there
occurs leakage of small amounts
of electrons
Which are transferred directly
to oxygen to form super oxide
ion (Free radicals/ROS)
What is a Free Radical ?
Any chemical species with one of more
unpaired electrons
Unstable/Highly Reactive to get
stabilized
Powerful Oxidant
Short half life (nanoseconds)
Can exist freely in environment
Main Factors Responsible for
ETC
Factors For Universal Metabolism
Nutrition
Environment
Life Style Habits
Factors Associated To ETC
Metabolites- Carbs ,Proteins , Lipids
Vitamins , Minerals and Antioxidants
Oxygen Concentration
Respiration Process
Hemoglobin Structure and Function
Mitochondrial DNA
Metabolic Status
Oxidative Stress
REGULATORS OF OXIDATIVE
PHOSPHORYLATION
Important Direct Substrates
Regulators Of Oxidative Phosphorylation
and ATP Generation
NADH/FADH2
O2
ADP and pi
Indirect Substances Involved
Glucose
Fatty acids
Insulin
Amino acids and Proteins
Iron
Vitamin C
Vitamin B Complex members- Niacin,
Riboflavin
ATP/ADP Ratio
Regulates Mechanism Of
Oxidative Phosphorylation
Respiratory Control
The most important factor in determining the rate of
oxidative phosphorylation is the level of ADP.
The regulation of the rate of oxidative phosphorylation by
the ADP level is cal ed respiratory control
ADP and pi is required for ETC
process.
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.
ADP levels reflect rate of ATP
consumption and energy state
of the cell.
At low ADP levels ? Low
oxidative phosphorylation
Electron transport is tightly coupled to
phosphorylation.
ATP cannot be synthesized by
oxidative phosphorylation unless there
is heat energy released from electron
transport.
Electrons do not flow through the
electron-transport chain to O2 unless
ADP is phosphorylated to ATP.
Inhibitors OF
ETC Complexes
OR
Inhibitors Of
Oxidative Phosphorylation
ETC Complexes Inhibitors
OR
Interruptors of Oxidative Phosphorylation
Mechanism
Enemies/Distractors of ETC components
who stop its normal operation.
Block ETC operation and stop ATP
generation.
ETC Complexes Inhibitors
Chemical compounds having affinity for ETC
components/complexes
Chemically interact with ETC complexes, bind and
inactivate them
Affects normal functional operation of ETC
Low/No ATP production
Cessation of cellular activities
Complex I/Site I - E.T.C Inhibitors
vAmobarbital /Amytal
vRotenone (Fish/Rat Poison)
vMercurials
vPiercidin ?A
(Volatile Anesthetics)
vHalothane (Malignant Hyperthermia)
vFluothane
vIsoflurane
vSevoflurane
Complex III/ Site II -E.T.C Inhibitors
vBritish Anti Lewisite ( BAL)
vAntimycin ?A
vDimercaprol
Complex IV/Site III /Cytochrome
Oxidase Inhibitors :
vCyanide
vCarbon Monoxide
vH2S
vAzide
Complex V Inhibitors
ATP Synthase Inhibitors
Oligomycin
Fo particle of ATP Synthase serve as
proton channel
An antibiotic Oligomycin binds with
Fo particle of ATP Synthase
Do not translocate Protons through
it.
Inhibits activation of ATP Synthase
phosphorylation of ADP to ATP.
Atractyloside
A Glycoside prevents
translocation of ADP across
mitochondrial membrane.
Make it unavailable for
phosphorylation reaction
Bongregate
Pseudomonas toxin has
inhibitory action similar
like Atractyloside.
Artificial Electron Acceptors/
Distractors Of ETC
These chemicals
arrest respiration
by inhibition of
ETC complexes
Specific inhibitors of
Electron Transport Chain
and
ATP-Synthase
Uncouplers Of
Oxidative
Phosphorylation
What are Uncouplers?
Uncouplers are chemical agents
Uncouplers are mostly lipid soluble
aromatic weak acids
They Uncouple/Delink two tightly
coupled natural processes
E.T.C (Oxidation) uncoupled from
Phosphorylation (ATP generation)
They just carry out Oxidation
without Phosphorylation
Uncouplers break the
connection between
Electron Transport Chain and
Phosphorylation
Electron transport is a motor
Phosphorylation is the transmission
Uncouplers put the car in NEUTRAL
Uncouplers Action Il ustrates
As Total Solar Eclipse
Uncouplers just bring oxidation
(E.T.C/Sun Rise) without
phosphorylation(Interrupted Sun Light)
Uncoupler (Moon In between) inhibits
generation of ATP ( Dark/No Day)
Types Of Uncouplers
Physiological Uncouplers
Thermogenin /Uncoupling Protein-1
Excess of Thyroxine
Long Chain Fatty acids
Unconjugated Hyperbilirubinemia
Chemical Uncouplers
2,4 Di Nitro Phenol
Di Nitro Cresol
Dicumarol
Aspirin
p-Triflouromethoxy Carbonyl Cyanide
Phenylhydrazone (FCCP)
Valinomycin
Pentachlorophenol
Snake Venom-Phospholipases
Mode Of Action Of Uncouplers
Certain Uncouplers are ionophores,
lipophilic substances.
They carry protons from
intermembrane space across
mitochondrial membrane to matrix
From site other than specific site.
(i.e not through F0 and F1 particles of
ATP Synthase).
Certain Uncouplers changes
permeability of mitochondrial
membrane to protons.
Translocate protons easily
through mitochondrial
membrane.
2,4 DNP dissolve in membrane and function as
carriers for H+.
Uncouplers block oxidative phosphorylation by
dissipating H+ electrochemical gradient.
Protons pumped out leak back into mitochondrial
matrix,
preventing development of proton gradient and
proton motive force.
ATP Synthase reaction runs backward
in presence of an uncoupler.
w Hydrolysis of ATP is spontaneous.
Thus Uncouplers by their action
deplete proton gradient of
intermembrane space during
ETC operation.
Uncouplers Dissipate More Heat
Uncouplers Do not allow to develop
required proton gradient and
Do not form proton motive force in the
intermembrane space of mitochondria
No translocation of Protons through ATP
Synthase
Causes no stimulation or activation of ATP
Synthase
No catalysis of Phosphorylation of ADP with
pi to generate ATP.
During uncoupling phenomena
Free energy released as Heat energy
more than 7.3 Kcal is not conserved for
Phosphorylation reaction dissipiated as
it is in form of heat
A very high heat energy released then
causes swelling of Mitochondria and
exhibit malignant hyperthermia.
Physiological Uncoupling
By
Uncoupling Protein (UCP-1)
An Uncoupling Protein (UCP-1)/
Thermogenin is produced in brown
adipose tissue of newborn mammals and
hibernating mammals.
This UCP-1 protein of an inner
mitochondrial membrane functions as a
H+carrier.
Uncoupling by UCP-1 protein blocks
development of a H+ electrochemical
gradient, thereby stimulating
respiration.
Free energy of ETC is dissipated as heat.
Uncoupling of ETC and
phosphorylation occurs in animals
as a means to produce heat
Non shivering thermogenesis
Occurs in brown adipose tissues
(rich in mitochondria)
Significance Of Physiological
Uncouplers
In extreme cold conditions and in
hibernating animals
Physiological Uncouplers bring
uncoupling phenomena
The heat liberated inside body helps
to restore and maintain body
temperature.
Brown adipose
(fat) cells
contain natural
Uncouplers to
warm animals
cold adaptation
and hibernation.
As per the Required condition Of
Body
This "non-shivering
thermogenesis" is costly in
terms of respiratory energy
Heat energy unavailable for
ATP synthesis
But provides valuable warming
to an organism.
Effect Of Poor Antioxidant Activity
ETC Inhibitors and Uncouplers
Any compound that stops
electron transport will stop
respiration...this means you
stop breathing
Electron transport can be
stopped by inhibiting ATP
synthesis
An uncoupler breaks the
connection between ATP
synthesis and electron
transport
Shuttle Systems
Shuttling Reducing Equivalents
OF NADH+H+
from Cytosol into the
Mitochondrion
Shuttle
A vehicle or aircraft that travels regularly
between two places
Biochemical shuttle is a biochemical
system for translocating Protons and
electrons produced during Glycolysis
Across a semipermeable inner membrane
of mitochondrion
For oxidative phosphorylation mechanism
NADH+H+ is generated in the cytosol during
Glycolysis
Cytosolic NADH+H+ itself is not
carried across the mitochondrial
membrane.
Instead its Protons and
Electrons of NADH+H+ are
carried through shuttle
systems.
Since NAD+ and NADH +H+ are
impermeable to an inner
mitochondrial membrane
This reducing equivalents must be
shuttled into mitochondrial matrix
before they can enter the ETC.
Cytosolic NADH+H+
Enter Mitochondria
via
2 Shuttle Systems
Two shuttles Involved:
Malate-Aspartate Shuttle
Glycerol 3-phosphate Shuttle
Malate-Aspartate Shuttle
Malate/Aspartate Shuttle System
Malate Aspartate Shuttle
Active in Heart and Liver.
2.5 molecules of ATP are produced
Glycerol-3-Phosphate Shuttle
Glycerol-3-Phosphate Shuttle
Glycerol 3 Phosphate Shuttle
Glycerol Phosphate Shuttle
Active in Skeletal muscles and
Brain
FADH2 formed in this enter the
electron-transport chain through
CoQ
Generates only 1.5 molecules of
ATP
Summary of Shuttle Systems
Total ATPs Generated / 1 Glucose Oxidation
Heart and Liver
32.0 ATP
Uses Malate Aspartate Shuttle
Muscle and Brain
30.0 ATP
Uses Glycerol phosphate Shuttle
Factors Affecting
Oxidative Phosphorylation
Mechanism
Oxygen supply to cells
Hemoglobin structure and function
Respiratory system and its function
Mitochondrial structure and ETC
components.
Presence of Nutrients
Enzyme function and
Coenzymes availability
Adequate amount of ADP
and pi.
Presence of ETC inhibitors
Pathological Conditions Affecting
Oxidation Phosphorylation
Mechanism
Which
Lower Down ATP Production
1. Hypoxia
2. Anemia
3. Ischemia
4. Hemoglobinopathies
5. Emphysema
6. Respiratory Distress Syndrome
7. Asthma
8. Prolonged Starvation
9. Malnutrition
10. Diabetes mellitus
11. ETC inhibition by chemicals/drugs
12. Inherited Disorders of Mitochondria
Inherited /Genetic Disorders
Related To Mitochondrial
Oxidative Phosphorylation
Mechanism
Mitochondrial DNA
Mitochondrial genes encode for ETC complexes
Complex I
Complex III
Complex IV
Complex V
Mutations in any one or more genes of
mitochondrial DNA controlling mechanism of Oxidative
phosphorylation lead to its inherited disorders
1. MELAS
An inherited disorder caused due to defect
of complex I or IV of E.T.C
Associated with
Mitochondrial Myopathy
Encephalopathy
Lactate accumulation
Acidosis
Stroke
2. Fatal Infantile Mitochondrial Myopathy
Defect in E.T.C components
located in mitochondria
Cytochrome c Oxidase defect
Associated with renal
dysfunction.
Mostly fatal in early age
3. Leber's Hereditary
Optic Neuropathy (LHON)
Caused due to mutations in
mitochondrial DNA
Affects oxidative
phosphorylation mechanism
Loss of bilateral vision due to
neuroretinal degeneration.
Mutant Genes Of LHON
4. Mitochondrial DNA Deletion
Syndrome
5. Luft's Disease
Luft's Disease is a mitochondrial disease
First patient who was diagnosed with this
disease was a 30 year old Swedish woman by
Dr Rolf Luft
Caused by abnormal mitochondria
Biochemical Cause
Mitochondria Respire Wildly
Respiratory control is lost
Partial Uncoupling is caused by an abnormality in
mitochondrial membrane
Electron transport is only loosely coupled to ATP
production
Oxidation process proceed independent of ADP
phosphorylation to generate ATP
An extra energy evolves in form of heat
This elevates body temperature up to 38.4 ?C which
raises BMR
Luft's Disease Is Characterized By
Abnormal excessive production of heat
Characterized by hypermetabolism and
abnormal transpiration.
Patient experiences excessive sweating
during winter
Make them to change their clothes 10 times a
day.
Onset is in childhood
Thyroid function is normal
Since there is less ATP production
and an extra energy is lost in the
form of heat
Metabolic processes are stimulated
Luft's Disease
Non Thyroidal Hypermetabolism
Due to high BMR and low ATP production
High caloric intake
There is failure to put on weight despite a good diet
There is progressive weight loss despite increased food
intake
Excessive perspiration
Excessive thirst indicate a state of severe hyper
metabolism of non thyroid origin (since thyroid hormones
-T3 and T4 are normal)
Manifestations of Luft's Disease
Heat intolerance
Profuse perspiration
Polydipsia without polyuria
Severe hyper metabolism
Polyphagia
Muscular wasting and weaken
Absent deep reflexes, and Resting
tachycardia.
Multiorgan Dysfunction Risk In
Luft's Disease
Case Study
An elderly couple was brought by ambulance to an emergency
department after their daughter noticed that they were both
acting "strangely." The couple had been in good health prior
to the weekend. Their daughter had gone out to spend the
week-end with her friends. The couple had been snowed in at
their house until the snowplows cleared the roads. They had
plenty of food and were kept warm by a furnace and blankets.
On reaching home after two days, their daughter noticed that
they both were complaining of bad headaches, confusion,
fatigue, and some nausea. On arrival to an emergency
department, both patients were afebrile with normal vital
signs and O2 saturation of 99 percent on 2 L of O2 by nasal
cannula. Their lips appeared to be very red. Both patients were
slightly confused but otherwise oriented. The physical
examinations were within normal limits.
Carboxyhemoglobin levels were drawn and were elevated.
What is most likely cause of these patients' symptoms?
Questions
Long Essays.
Q.1 Define Biological oxidation.
Enumerate and Describe various
enzymes carrying out biological
oxidation reactions with suitable
examples.
Q.2 Describe Respiratory chain and
Give its significance.
OR
Explain the Electron. Transport chain
(E.T.C.) and its significance.
OR
How the reduced equivalents generated
in anaerobic dehydrogenase reactions
are reoxidized.
Q.3 What is oxidative
phosphorylation? Explain
the mechanism with
respect to various theories
and hypothesis.
Short Notes
Cytochromes
Inhibitors of E.T.C
Shuttle systems and its
significance
Inhibitors and Uncouplers of
oxidative phosphorylation
Complexes of E.T.C.
Redox potential and free energy
changes.
Inherited Disorders related to E.T.C.
abnormality.
ATP ? Mode of its formation and
it's role in the Body.
Short Answer Questions
Give the sites for ATP generation
of in E.T.C.
Enumerate the High energy
compounds of our body
Substrate level phosphorylation
and it's importance.
Enumerate the Enzymes
catalyzing Biological oxidation
reactions. Write the class to
which these enzymes classified.
Inherited Disorders of
Mitochondrial Dysfunction
Define P.O ratio. What is the P:O
ratio for reduced NADH+H+ &
FADH2 respectively.
List the components of E.T.C. and
their location.
Redox couple & Redox potential.
FlavoProteins
Product of Aerobic and
Anaerobic dehydrogenation
reactions.
Write enzymes catalyzing
Aerobic and Anaerobic
dehydrogenation reaction's
during metabolism.
THANK YOU
Laboratory data showed lactic acidosis,
Proteinuria
Glycosuria and
Generalized aminoaciduria
Muscle biopsy showed large clumps of
granules positive with oxidative enzyme
stains and increased lipid droplets.
Ultrastructural studies showed large
aggregates of mitochondria, many of which
were greatly enlarged and contained
disoriented or concentric whorls of cristae
and paracrystalline inclusions.
A 1-month-old boy was admitted because of failure to thrive.
He was floppy and had bilateral ptosis, diminished reflexes, and
poor suck. He had aspiration pneumonia, developed seizures,
and died at age 3 1/2 months.
He was an only child, and family history was negative.
Cytochrome c oxidase was absent in fresh frozen sections
by histochemical staining.
By biochemical assay, cytochrome c oxidase (cytochrome aa3)
was 6% of normal in muscle biopsy and undetectable in autopsy
muscle; spectra and content of cytochromes showed lack of
cytochrome aa3, decreased cytochrome b and normal
cytochrome cc1.
In kidney, cytochrome-c-oxidase activity was 38% of normal
and spectra showed decreased cytochromes aa3 and b.
The association of fatal infantile mitochondrial myopathy,
lactic acidosis and renal dysfunction was previously reported
by Van Biervliet et al and appears to be a distinct nosologic
entity, one of the few biochemically defined mitochondrial
myopathies.
A case of cytochrome c oxidase deficiency primarily affecting
skeletal muscle is described. The child was admitted at 4
weeks due to failure to thrive and examination at that time
revealed weakness and hypotonia. His condition deteriorated
until at 11 weeks respiratory arrest necessitated artificial
ventilation and death occurred at 14 weeks. Biochemical
investigation showed lactic acidemia and generalized
aminoaciduria. Histochemical examination of muscle obtained
at biopsy showed strong reactions for some oxidative enzymes,
but by contrast cytochrome c oxidase could not be detected.
Cytochrome c oxidase activity was less than 5% of control
values in an extract of fresh muscle. The reduced-minus
oxidized absorption spectra of muscle mitochondrial fractions
prepared from post-mortem tissue showed an absence of
cytochrome aa3 and a partial deficiency of cytochrome b. Ultra
-structural examination showed abnormal mitochondria with
loss of cristae and an abnormal granular matrix. The family
history suggests autosomal recessive inheritance.
This post was last modified on 05 April 2022