Final answer:
Energy is released when a phosphate group is removed from ATP to form ADP, as high-energy bonds (phosphoanhydride bonds) are broken during the reaction.
Step-by-step explanation:
When a phosphate group is removed from ATP to form ADP, energy is released. The process of removing a phosphate group from ATP to form ADP is known as dephosphorylation. This reaction involves breaking the high-energy bond — specifically known as a phosphoanhydride bond — between the phosphate groups within ATP. The removal of a phosphate group, often through a hydrolysis reaction, involves water and results in the formation of ADP (adenosine diphosphate) and a free phosphate group. The energy that is released during this reaction is substantial and is used by the cell to carry out various important processes, such as muscle contraction and nerve impulse propagation.
The bonds between phosphate groups are high energy because the negatively charged phosphate groups naturally repel each other, making the ATP molecule inherently unstable. The energy to bond the phosphate groups is significant, and accordingly, when these bonds are broken, a corresponding amount of energy is released, thereby making this energy available for the cell to do work.