Final answer:
A 'high energy' bond stores a significant amount of energy that is released upon hydrolysis; in ATP, this refers to the phosphoanhydride bonds between phosphate groups. The breaking of these bonds forms ADP and Pi, releasing energy for cellular activities.
Step-by-step explanation:
For a bond to be considered "high energy," such as the bonds between phosphate groups in ATP (adenosine triphosphate), it means that the bond stores a significant amount of energy that, when broken, can release sufficient energy to drive various cellular processes.
The bonds in ATP that are referred to as high-energy are the phosphoanhydride bonds between the second and third (beta and gamma) phosphate groups and between the first and second phosphate groups. When these bonds are broken via hydrolysis, the reaction results in the formation of adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) while releasing free energy that the cell can utilize for activities such as muscle contraction, nerve impulse propagation, and the synthesis of biomolecules.
The term "high-energy" bonds comes from comparing the free energy of the reactants and products; ATP and a water molecule have a higher free energy than the products (ADP and Pi). This energy is essential for driving endergonic reactions in the cell, making ATP the primary energy currency within biological systems.