What is ATP? respiration of Biology

Adenosine triphosphate
Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism. It is produced as an energy source during the processes of photosynthesis and cellular respiration and consumed by many enzymes and a multitude of cellular processes including biosynthetic reactions, motility and cell division. In signal transduction pathways, ATP is used as a substrate by kinases that phosphorylate proteins and lipids, as well as by adenylate cyclase, which uses ATP to produce the second messenger molecule cyclic AMP.
The structure of this molecule consists of a purine base (adenine) attached to the 1' carbon atom of a pentose sugar (ribose). Three phosphate groups are attached at the 5' carbon atom of the pentose sugar. ATP is also incorporated into nucleic acids by polymerases in the processes of DNA replication and transcription. When ATP is used in DNA synthesis, the ribose sugar is first converted to deoxyribose by ribonucleotide reductase. ATP was discovered in 1929 by Karl Lohmann,[1] and was proposed to be the main energy-transfer molecule in the cell by Fritz Albert Lipmann in 1941.[2]

Ionization in biological systems
ATP has multiple ionizable groups with different acid dissociation constants. In neutral solution, ATP is ionized and exists mostly as ATP4−, with a small proportion of ATP3−.[7] As ATP has several negatively-charged groups in neutral solution, it can chelate metals with very high affinity. The binding constant for various metal ions are (given as per mole) as Mg2+ (9 554), Na+ (13), Ca2+ (3 722), K+ (8), Sr2+ (1 381) and Li+ (25).[8] Due to the strength of these interactions, ATP exists in the cell mostly in a complex with Mg2+.[9][7]