|Molecular formula||C 10 H 15 N 5 O 10 P 2|
|External identifiers / databases|
|Molar mass||427.20 g mol −1|
|As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .|
Adenosine with a one-part phosphorus chain is analogously called adenosine monophosphate (AMP); with a three-part phosphorus chain it is called adenosine triphosphate (ATP). Of these three molecules, ATP is the most energetic molecule - AMP the least energetic.
The designation high-energy or low-energy is actually misleading. The bonds are by no means strong, but rather unstable. Since all three phosphate groups are negatively charged in biological systems and are packed close together, they repel each other; comparable to a tensioned spring. The divalent magnesium ion coordinated under physiological conditions stabilizes this tension somewhat.
The phosphorylation of substrates by means of ATP produces ADP, which can generally be formulated as follows:
The bond between the second and third phosphate of the phosphate chain is broken and the substrate is phosphorylated. The product is more energetic than the substrate. The energy-poor ADP is phosphorylated back to energy-rich ATP through energy-supplying reactions in the body. In all eukaryotes these reactions take place in the mitochondria , a special organelle of the cell. In plants that carry out photosynthesis , these build-up and breakdown reactions also take place in the chloroplasts .