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Structure

Adenosine triphosphate is a Nucléotide triphosphate. It is made up:

of Adenosine, therefore of Adénine and Ribose (β-D-ribofurannose),
and of three groupings phosphates.

Role

Energy source

Because of presence of connections rich in energy (those binding the groupings phosphate are connections Anhydride of acid), this Molécule is used at the living beings to provide energy to the chemical reactions which consume some. The ATP is the reserve of energy of the cell.

Indeed, the reaction of Hydrolysis of adenosine triphosphate in Adenosine diphosphate (figure 3) and Phosphate are a reaction Exergonique: the variation of Enthalpie free standard is equal to −30 kJ/mol: $\ mathrm {ATP} + \ mathrm {H_ {2} O} \ longrightarrow \ mathrm {ADP} + \ mathrm {P_ {I}}$

On the contrary, the reaction of synthesis of adenosine triphosphate starting from adenosine diphosphate and of phosphate is a reaction Endergonique: the variation of Enthalpie free standard is equal to +30 kJ/mol. $\ mathrm {ADP} + \ mathrm {P_ {I}} \ longrightarrow \ mathrm {ATP} + \ mathrm {H_ {2} O}$

The reaction of hydrolysis of the ATP out of adenosine monophosphate (and pyrophosphate) is a exergonic reaction: the variation of Enthalpie free standard is equal to −42 kJ/mol. $\ mathrm {ATP} + \ mathrm {H_ {2} O} \ longrightarrow \ mathrm {AMP} + \ mathrm {P_ {I}} \ sim \ mathrm {P_ {I}}$

Energy is thus stored in the connections between the groupings phosphates.

There exists however a stage of Enthalpie to be crossed before releasing this energy. This explains why the hydrolysis of the bonds pyrophosphate does not occur permanently. The enzymes are able to lower this threshold, in order to use released energy.

If the energy is thus stored in the connections pyrophospate, one can wonder which is the interest for the living beings to synthesize the whole molecule, and not only of pyrophosphate free. The answer is probably in the capacity of the Enzymes to recognize the ATP, easier to hydrolize specifically than pyrophosphate free, very similar to all the groupings phosphates present in the Biomolécules.

The ADP can be phosphoryl by the respiratory Chaîne of the Mitochondrie S and the Procaryote S or by the Chloroplaste S vegetable to give again ATP. The Coenzyme ATP/ADP is a universal donor of energy, and it is the independent source of energy directly usable by the cell. At the human one, the ATP constitutes only energy usable by the muscle.

Cellular messenger

The cyclic Adénosine monophosphate (or AMPc) under the action of a Hormone is one of the means of communicating messages inside the cell by the membrane receivers.

Storage of the ATP

Stocks of ATP of the organization do not exceed a few seconds of consumption. In theory, ATP is produced permanently, but any process which blocks its production (what is the case of certain poison gases designed for this purpose) causes consequently a fast death of the contaminated organization.

At this point in time the molecules of Créatine intervene: they just like bind a phosphate by a connection rich in energy the ATP. The ADP can thus thus become again of the ATP by coupling with the hydrolysis of creatin-phosphate. Creatin thus recycles to some extent phosphate released by hydrolysis of the molecule of original ATP.

The ATP cannot be stored in a rough state, only of the intermediaries of the line production of the ATP can be stored. Example of the Glycogène which will be able to be transformed into glucose and to feed glycolysis if the organization needs more than ATP.

See too

External bonds

Simple: Adenosine Triphosphate

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