This document discusses the ATP cycle and ATP's role as a carrier of chemical energy in cells. It defines high-energy compounds as those that can liberate at least 7 Calories per mole and lists several examples. ATP is generated through catabolic pathways and broken down to power anabolic reactions, transport processes, and mechanical work. When ATP breaks down, it transfers its chemical energy to drive these various energy-requiring cellular processes.

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 PO4
3-
(exception acetyl CoA) hence they are called
high E phosphate compounds.

3. Compounds ΔG0
(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 10
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.