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Adenosine triphosphate

Synonyms: Adenosine-5'-triphosphate
German: Adenosintriphosphat, ATP

1 Definition

Adenosine triphosphate, ATP for short, is a molecule belonging to the group of mononucleotides which contains three energy-rich phosphate groups that are attached through anhydride bonds. Because of the energy stored in those bonds, ATP serves as the primary energy reservoir within cells.

2 History

ATP was discovered in 1929 by German biochemist and physiologist Karl Lohmann.

3 Chemistry

Adenosine triphosphate has the molecular formula C10H16N5O13P3 and a molecular mass of 507.18 g/mol.

Adenosine triphosphate consists of the adenine molecule which binds to the pentose monosaccharide ribose through an N-glycosidic bond (adenosine). Attached to the 5'-end are three phosphate groups. The first phosphate group (α phosphate) binds through a organophosphate bond, whereas the β and γ phosphates are connected by phosphoric acid anhydride bonds.

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4 Synthesis

The molecule is created from ADP through a single phosphorylation or from adenosine through three consecutive phosphorylation steps. The activated phosphate groups that are required for this step originate either from other energy-rich molecules like phosphocreatine, some metabolites of glycolysis (substrate-level phosphorylation), or they are attached to the molecule during the reactions of the respiratory chain (oxidative phosphorylation) in mitochondria, using FADH2 and NADH.

5 Physiology

About half of all the energy taken in by an organism can be utilized to supply energy for different metabolic pathways. The synthesis of ATP plays a central role: After the elapse of the citric acid cycle in mitochondria, redox equivalents in the form of NADH and FADH2 are formed, and are later used for the formation of adenosine triphosphate by the enzymes of the respiratory chain.

5.1 Utilization

The largest share of ATP consumption is represented by the active transport of ions through the cell membrane, besides that, however, adenosine triphosphate is also required for the synthesis of biological molecules, the transport of particles within the cell, or the movement of cellular parts and muscles.

5.2 Regulation

The regulation of ATP concentration in cells is crucial to the functioning of an organism. It is realized by several mechanisms:

  • Decreasing ATP concentration directly or indirectly increases the activity of enzymes of glycogen and fat breakdown, as well as those of glycolysis; this results in increased energy extraction from stored energy reserves.
  • Contrary to that, increased ATP levels lead to the inhibition of energy-supplying pathways and to the expansion of energy reserves (e.g. glycogen or fat) in different tissues.
  • Note: The daily amount of ATP required by all the cellular processes of an organism is roughly equivalent to the mass of that organism. A man of normal weight, for instance, uses (and regenerates) about 70 kg of adenosine triphosphate daily.

6 Clinical significance

ATP is used in medical therapy as a vasodilator.

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