Answer:
ADP
Explanation:
Your question: The release of one phosphate group from ATP powers the reactants in the cell which phosphate is the one that is released from ATP
My answer: ADP
Why is my answer correct?
If a cell needs to spend energy to accomplish a task, the ATP molecule splits off one of its three phosphates, becoming ADP (Adenosine di-phosphate) + phosphate. The energy holding that phosphate molecule is now released and available to do work for the cell.
Hope this helps! :)