Why do you call ATP as universal energy currency of cell?

Explanation

ATP is a nucleotide consisting of a base-adenine, a pentose sugar-ribose and three phosphate group. Out of three phosphate groups the last two are attached by high energy rich bonds. On hydrolysis, it releases energy (7.3 K cal or 30.6 KJ/ATP) and it is found in all living cells and hence it is called universal energy currency of the cell.