introduction f0 f1 AT pase model chemiosmotic regeneration of ATP during respiration role in ATP synthesise

1. Chemiosmotic regeneration of ATP during
respiration, FO-F1 Model of ATPase &
Role in ATP synthesis
Presented by,
Sumra kazbanu Abdula
M.Sc sem - 3
CBO 501
Department of life sciences,
H.N.G.U Patan

2. CONTENTS
• Introduction
• FO- F1 ATPase model
• Chemiosmotic regeneration of ATP during
respiration
• Role in ATP synthesis

3. Introduction
• In the ETC ,the successive electron acceptors are
at lower & lower energy levels.
• With each transfer to a lower energy level, the
electrons release some of their potential energy.
• This is why this series is called an electron
cascade, like a cascade of falling water.
• Since ,electron transport involves oxidation as
well as phosphorylation this process by which cell
system traps chemical energy is called oxidative
phosphorylation.

4. FO-F1 ATPase model
• The mitochondrial inner membrane contains the ATP
synthesizing enzyme complex called ATP Synthetase or
F0 -F1 ATPase .
• This enzyme complex has 2 major components F0 and
F1.
• The F1 components was first extracted from the
mitochondrial inner membrane and purified by Efraim
Racker and his collaborators in 1960.
• Racker found that the addition of these F1 spheres to
the stripped mitochondrial particles restored their
capacity to synthesize ATP.

5. Model of F0 F1 ATPase

6. • The cristae membranes are fragmented which
,later on , reseal to form vesicles called
submitochondrial particles, in which the F1
spheres are on the out side, rather than the
inside.
• the isolated F1 alone cannot make ATP from ADP
and inorganic phosphate but it can hydrolyze
ATP to ADP and phosphate.
• It is , therefore, also called as F1 ATPase.

7. • The spheric F1 components contains 9
polypeptide chain subunit of five kinds arranged
into a cluster. It has many binding sites for ATP
and ADP.
• The cuboidal F0 component is a hydrophobic
segments of 4 polypeptide chains.
• It act as a base piece and normally extends
across the inner membrane.
• F0 is the proton channel of the enzyme complex.

8. • The cylindric stalk between F0 and F1 includes
many other proteins.
• One of them renders the enzymes complex
sensitive to oligomycin, an antibiotic that blocks
ATP synthesis by interferring with the utilization
of the proton gradient.
• The stalk is the communicating portion of the
enzyme complex.
• F0F1 ATPase is called an ATPase because, in
isolated form, it hydrolyzes ATP to ADP plus Pi.

9. Chemical coupling Hypothesis:
• The hypothesis,thus, postulates direct chemical
coupling at all stages of the process. It is similar
to the concept in glycolysis which states that the
ATP produced in oxidative phosphorylation results
from an energy rich intermediate encountered in
electron transport.
• Oxidative phosphorylation occurs in certain
reactions of glycolysis, in the citric acid cycle and
in the respiratory chain.

10. • However, it is only in those phosphorylation
occuring at the substrate level in glycolysis and the
citric acid cycle that the chemical mechanism
involved are known.
• However,at present,the identities of the
hypothetical high energy carrier and the postulated
intermediates I and X are not known. In recent
years,several so called "coupling factors " have been
isolated that restore phosphorylation when added to
disrupted mitochondria.

11. Conformational coupling Hypothesis:
• In mitochondria,that are actively phosphorylating in
the presence of an excess of ADP, The inner
membrane pulls away from the outer membrane and
assumes a " condensed state" .In the absence of ADP,
the mitochondria have the normal structure or the "
swollen state".
• In which the crustae project into the large matrix. The
propounders of this hypothesis believe that the
energy released in the transport of electron along the
respiratory chain causes the condemnational changes,
just described, in the inner mitochondrial membrane
and that this energy rich condensed structure.

12. Chemiosmotic regeneration of ATP during
respiration:
• This is a simpler radically different and novel
mechanism and was postulated by Peter Mitchell,
a British biochemist , in 1961.
• He proposed that electron transport and ATP
synthesis are coupled by a proton gradient, rather
than by a covalent high energy intermediate or an
activated protein.

13. • According to this theory, the inner membrane of
the mitochondria acts as a transducer converting
the energy which is provided by a electrochemical
gradient, into the chemical energy of ATP.
• The election transport system is organised in "
redox loops" within the membrane,and the
electrons are passed from one carrier to another
on the respiratory chain.

14. Chemiosmotic coupling Hypothesis

15. • At the same, time protons (H+) are ejected
toward the cytoplasmic side (C side) , while OH-
remain on matrix side.
• This vectorial movement of protons creates a
difference in pH ,which results in an electrical
potential.
• Calling pH the pH gradient and ¥ the resulting
electrical gradient in volts, the energy produced
delta P is the proton motive force (PMF ):
Delta P= delta ¥ + 2.3 RT/F delta pH

17. • The chemiosmotic theory postulates that the
primary transformations occurring in the
respiratory chain guide the osmotic work needed
to accumulate ions.
• This gradient provides the driving force for the
inward transport of phosphate and potential for
generating ATP.
• ADP is brought into matrix in exchange for ATP
i.e. cotransport.

18. • The proton pump of the F0 - F1, drives the
oxidative phosphorylation of ADP to form ATP by
which mechanism free energy is conserved.
• In recent years, much experimental evidence has
supported the validity of Mithchell's
chemiosmotic theory.
• However, there is some dispute over the number
of H+ ions translocated out during two -electron
transportation from NADH to oxygen.

19. Role in ATP synthesis:
• Like other enzymes, the activity of F1FO ATP
synthase is reversible.
• Large-enough quantities of ATP cause it to creat
trans membrane proton gradient, this is used by
fermenting bacteria that do not have an electron
transport chain, but rather hydrolyze ATP to make
a proton gradient, which they use to drivepr
flagella and the transport of nutrients into the
cell.

21. • In respiring bacteria under physiological conditions,
ATP synthase, in general, runs in the opposite
direction, creating ATP while using the proton
motive force created by the electron transport
chains a source of energy.
• The overall process of creating energy in this fashion
is termed oxidative phosphorylation. The same
process takes place in the mitochondria, where ATP
synthase is located in the inner mitochondrial
membrane and the F1-part projects into
mitochondrial matrix.
• The consumption of ATP by ATP-synthase pumps
proton cations into the matrix.

22. Reference
• Principles of biochemistry
By: Albert lehninger
• plant Physiology
By: Taiz & Zeiger
• Cell biology,Genetics, Molecular biology,Evolution
and Ecology
By : Dr. P.S.Verma
Dr. V.K. Agarwal