What is the role of ATP and ADP in cellular respiration???

ATP and ADP are energy molecules (adenosine triphosphate and adenosine diphosphate, respectively). In ATP there are 3 phosphate groups, hence triphosphate. When you break off one of those phosphates you release energy, and it becomes adenosine diphosphate. Adding one will store energy in it. Therefore ATP and ADP provide energy to help start processes in cell respiration by providing energy. Same with photosynthesis. ATP releases a phosphate group in order to help carry out some of the parts of photosynthesis.