ATP Cycle

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Bio-inorganic chemistry:

Bio-inorganic chemistry ATP CYCLE M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Research Scholar

High energy compounds:

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 . High energy compounds

High E compounds:

High E compounds Compounds Δ G 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

Low E Phosphates:

Low E Phosphates 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

Classification of High E compounds:

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 Classification of High E compounds


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., ATP CYCLE


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. ATP CYCLE


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. ATP CYCLE


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. ATP CYCLE


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. ATP CYCLE


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. ATP CYCLE

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