Final answer:
In ATP, the bond between one phosphate group option (c) (the beta and gamma phosphates) is broken to release energy during chemical reactions, converting ATP to ADP and a phosphate group.
Step-by-step explanation:
The part of ATP (adenosine triphosphate) that is broken to release energy for use in chemical reactions is one phosphate group, specifically the bond between the beta and gamma phosphate groups.
When cells require energy to do work, enzymes break the high-energy bond between the second and third phosphate groups. This hydrolysis reaction effectively converts ATP to adenosine diphosphate (ADP) and an inorganic phosphate group (Pi), releasing the energy stored in the bond. The released energy is then utilized to power various cellular processes and reactions.
The reaction that breaks the bond and releases energy is expressed as ATP + H2O → ADP + Pi + free energy; this is a key step in cellular metabolism.