Answer:
ADP
Step-by-step explanation:
In the cytoplasm of cells, it is common for a soluble substance known as adenosine diphosphate, ADP. It is also common to have soluble radicals free of inorganic phosphate (which we will symbolize by Pi), monovalent anions of orthophosphoric acid. Each time energy is released in aerobic respiration, this energy binds inorganic phosphate (Pi) to ADP, generating ATP. The opposite reaction also happens, when ATP releases energy, one of the inorganic phosphates dissociates from the molecule, releasing ADP.