Synthesis of ATP in humans

1. Dr. Ashok Kumar J
International Medical School
Management and Science University
Malaysia

2. Oxidation is defined as the removal of electrons
e- (Electron)
Fe2+ Fe3+
e- (Electron)
Cu+ Cu2+
Reduction as the gain of electrons
Oxidation is always accompanied by reduction of an
electron acceptor
Fe2+ + Cu2+ Fe3+ + Cu+
Dr. Ashok Kumar J; Professor; Biochemistry

3. Higher organisms dietary fuels are metabolized to:
1. Carbon dioxide (CO2 ; Fully oxidized form of carbon)
2. Water fully reduced form of oxygen
Fuels
Oxidized
Electrons are
transferred to
coenzymes
ETC
ADP ATP
CO2
H2O
½O2
Dr. Ashok Kumar J; Professor; Biochemistry

4. Cytoplasm
Pyruvic acid
Mitochondrion
Dr. Ashok Kumar J; Professor; Biochemistry

5. Dr. Ashok Kumar J; Professor; Biochemistry

6. Dr. Ashok Kumar J; Professor;
Biochemistry
MITOCHONDRIA

7. ELECTRON TRANSPORT CHAIN
There are four different complexes
Complex I, II, III, IV,
Dr. Ashok Kumar J; Professor; Biochemistry

9. Dr. Ashok Kumar J; Professor; Biochemistry

10. Peter D. Mitchell
United Kingdom
Glynn Research
Laboratories
Bodmin, United Kingdom
b. 1920
d. 1992
Mitchell’s hypothesis explains
Mechanism of Oxidative
phosphorylation
Dr. Ashok Kumar J; Professor; Biochemistry

11. Mitchell’s chemiosmotic theory
Energy from oxidation of components in
the respiratory chain is coupled to the
translocation of hydrogen ions (protons,
H+) from the inside to the outside of the
inner mitochondrial membrane.
Complexes I, III, and IV acts as a
proton pump
Dr. Ashok Kumar J; Professor; Biochemistry

12. Dr. Ashok Kumar J; Professor; Biochemistry
The transfer of two electrons
from NADH+ H+ to O2 is
accompanied by the outward
pumping of 10 H+
Complex I and complex III
pumps 4 protons each
Complex IV pumps 2 protons
To inter-membranous space
10 protons are pumped by the
electron transport chain
10 protons are pumped out per NADH
1. 4 must flow in to produce 1 ATP
2. The proton-based P/O ratio is 2.5 for NADH as the electron donor and 1.5
(6/4) for succinate

13. ATP synthase
1. ATP Synthesizing enzyme complex
2. Two major components (F0 and F1)
3. F1 in all aerobic organisms consists of
- α3β3γδε subunits
- binding sites for ATP and ADP
- Catalytic site for ATP synthesis
Dr. Ashok Kumar J; Professor; Biochemistry

14. Dr. Ashok Kumar J; Professor; Biochemistry
P:O Ratio
Number of moles of inorganic phosphate consumed
per atom of oxygen utilized
Phosphate group esterified
P:O ratio =
Electron pairs transferred
Number of moles of inorganic phosphate consumed
per atom of oxygen utilized

15. Paul Boyer (1964) proposed that a conformational
change in the mitochondrial membrane protein
leads to synthesis of ATP
Paul Boyer hypothesis is now considered as
- rotatory motor
- engine driving model
- binding change model
To explain generation of ATP
Dr. Ashok Kumar J; Professor; Biochemistry

16. In response to proton influx ‘γ’ subunit physically rotates
This induces conformational change in the β3 subunit
β Subunit can adopt different conformations
Loose (L) conformation - (ADP and Pi bind )
Tight (T) conformation - (Tightly bound ATP)
Open (O) conformation - (Release ATP)
Dr. Ashok Kumar J; Professor; Biochemistry

17. [ATP]
Dr. Ashok Kumar J; Professor; Biochemistry
[ADP] [Pi]
[NADH]
[NAD+]
Increases rate of mitochondrial respiration
Enhanced oxidative phosphorylation
Increased ATP synthesis
Cellular activity
ATP is used
ADP concentration
increased
Increased rate of
catabolism of nutrients
Mitochondrial ADP
concentration has
important role in
regulating oxidative
phosphorylation
RESPIRATORY
CONTROL
ADP transport across the inner mitochondrial membrane can be inhibited by
Atractyloside
It can inhibit oxidative phosphorylation

18. Uncouplers
Uncouplers is to dissociate oxidation in the respiratory
chain from phosphorylation
Compounds are toxic in vivo, causing respiration to become
uncontrolled, since the rate is no longer limited by the
concentration of ADP or Pi
Uncouplers
2,4 dinitro phenol
Dinitrocresol
Pentachlorophenol
CCCP (m-chlorocarbonyl- cyanide phenyl hydrazine)
Dr. Ashok Kumar J; Professor; Biochemistry

19. Dr. Ashok Kumar J; Professor; Biochemistry
Physiological uncouplers
Thyroxine
Long chain free fattyacids
Unconjugated bilirubin
Ionohores
Valenomycin (Ionophore for K+ ions)
Nigercin (Ionophore for K+ ions)
Electron transport chain continues; energy is released as heat

20. Brown adipose tissue
Dr. Ashok Kumar J; Professor; Biochemistry
Characterized by
- High content of mitochondria
- High content of cytochrome
- Well developed blood supply
- Relatively rich in carnitine
- Has low ATP synthase activity
- High oxygen consumption
- Involved mainly in metabolism particularly at times when
heat generation is required
Brown color is due to relatively high content of mitochondria

21. Tissue is extremely active in
In some species in arousal from hibernation
In animals exposed to cold (non-shivering thermogenesis)
In heat production in the newborn animal
• Shown to be active in normal individuals
• Responsible for diet induced thermogenesis
‘Eat and do not get fat
Dr. Ashok Kumar J; Professor; Biochemistry

23. Disorders of mitochondrial function
• About 100 polypeptides are required for oxidative phosphorylation
• 13 of these polypeptides are coded by mitochondrial DNA (mtDNA) and
synthesized in the mitochondria
Mitochondrial is maternally inherited
(Mitochondria from the sperm do not enter the fertilized ovum)
Mitochondrial DNA is about 10 times more susceptible to mutations than
nuclear DNA
Dr. Ashok Kumar J; Professor; Biochemistry

24. Mitochondrial Myopathies
May result in cell death
Particularly affect skeletal and cardiac muscles
Dr. Ashok Kumar J; Professor; Biochemistry
Characterized by
- Accumulation of lactic acid
- Myopathies
- Cardiomyopathies
- Encephalopathies
• Characterized by the presence of mitochondria with abnormal shape and size
• Typically results in muscle fibers appearing as ragged red fibers
( Muscle biopsy; Gomori trichrome or other stains)

25. Courtesy of Dr Ana Sotrel
Gomori trichrome stain.
Mitochondrial myopathy.
There are several isolated
muscle fibers with red
granular staining and
disruption of fiber structure.

26. Mitochondrial encephalomyopathy lactic acidosis stroke
like episodes (MELAS)
A. MRI of the brain showing atrophy
and enhancing low attenuation
lesions.
B. B. Gomori trichrome stain showing
a ragged red fiber (black arrow) and
two severely atrophic denervated
fibers (white arrow).
- Complex I defect; Lactic acidosis,
strokes,myopathy,seizures, dementia

27. Leber's hereditary optic myopathy (LHON)
• Characterized by blindness in young males
• Caused by a single base mutation in NADH Coenzyme Q
reductase
• Streptomycin induced deafness is also found to be due to a
mutation in the mitochondrial rRNA
Myoclonic epilepsy ragged red fiber disease (MERRF)
• Myoclonic epilepsy, myopathy, dementia
Leigh's syndrome
• Complex I defect; Movement disorders

28. Dr. Ashok Kumar J; Professor; Biochemistry