ATP cycle

energy and role of ATP cycle

1. ATP CYCLE
M.Prasad Naidu
MSc Medical Biochemistry,
Ph.D.Research Scholar

2. The term high-E compounds or energy rich
compounds is usually applied to substances
which possess sufficient free E to liberate at
least 7 Cal/mol at pH 7.0
The compounds which liberate less than 7.0
Cal/mol are referred to as low-E compounds.
Most of the high E compounds contain PO
4
3-
(exception acetyl CoA) hence they are called
high E phosphate compounds .

3. Compounds ΔG
0
(Cal/mol)
Phosphoenol pyruvate -14.8
Carbamoyl phosphate -12.3
Cyclic AMP -12.0
1,3bisphosphoglycerate -11.8
phosphocreatine -10.3
Acetyl phosphate -10.3
SAM -10.0
Pyrophosphate -8.0
Acetyl CoA -7.7

4. ADP→AMP+Pi -6.6
Glucose-1-
phosphate
-5.0
Fructose-6-
Phosphate
-3.8
Glucose-6-
phosphate
-3.3
Glycerol-3-
phosphate
-2.2

5. 1. Pyrophosphates e.g. ATP
2. Acyl phosphates e.g. 1,3-bisphosphogly
3. Enol phosphates e.g. PEP
4. Thioesters e.g. acetyl CoA
5. Phosphagenes e.g. phosphocreatine

6. The living objects require a continuous supply of
FE mainly for
1. to synthesize macromolecules from simpler &
smaller precursors
2. to transport molecules and ions across
membranes against gradients and
3. to perform mechanical work, as in the muscle
contraction etc.,

7. The FE in these processes is derived from the
environment.
The phototrophs obtain this E by trapping light E from
the SUN.
On the other hand, chemotrophs obtain it by the
oxidation of food stuffs.
This FE is partly transformed into special form b4 it is
used for biosynthesis, tpt, motion and fidelity.
This special carrier of FE is ATP.
ATP plays a central role in the transference of FE from
exergonic to the endergonic processes in the cells.

8. ATP donates much of its chemical E to energy
requiring processes (biosynthesis, transport) by
undergoing a breakdown to ADP and Pi.
ATP was discovered in extracts of skeletal
muscles by Karl Lohmann in GE and by
Cyrus Fiske and Y.Subbarow (US)
simultaneously in 1929.
Later it was found to be present in all types of
cells- animal, plant and microbial.

9. Fritz.A.Lipmann a GE born US biochemist
postulated that ATP is the 1
0
and universal
carrier of chemical E in cells.(Nobel prize)
He also first proposed the ATP Cycle , and is
popularly known as Father of ATP cycle.
He introduced squiggle notation to designate E
rich bonds of biomolecules such as ATP and
ADP.

10. ATP, ADP & AMP occur not only in cell cytosol
but also in MC and the nucleus.
ATP serves as the principal immediate donor of
FE in biological systems rather than as a
storage form of E.
In a typical cell, an ATP molecule is consumed
with in a minute of its formation.
The turnover of ATP is very high.
For instance , a resting human consumes about
40kg ATP in a day.

11. The endergonic processess such as bio-
synthesis, active tpt etc can occur only if ATP is
continuously regenerated from ATP
Phototrophs harvest the FE in light to regenerate
ATP where as chemotrophs form ATP by the
oxidation of food stuffs.