Atp serves as a common energy source for organisms because

The reasons why Adenosine Triphosphate is a common energy source for all organisms is that: 1. It is a high-energy molecule 2. ATP has an unstable structure compared to other high-energy molecules. 3. ATP has higher potential to transfer phosphate group.

Explanation:

The transfer of phosphate group from high energy molecule like the adenosine triphosphate (ATP) usually release energy that is required by most of cellular activities, thus this dephosphorylation process is an exergonic reaction. While other molecules like the GTP can give energy, these molecules are more stable structurally and breaking them down will not by energetically wise, thus there is need to use a less stable high energy molecules like the ATP which have the potential of releasing their phosphate radical more easily. This is the reason why all organisms make use of the ATP molecule as the only energy source.