Advanced Placement (AP) Biology Practice Exam

What occurs when a phosphate group is released from ATP?

1. It stabilizes the molecule

2. It energizes the molecule

3. It destabilizes other molecules

4. It initiates exergonic reactions

The correct answer is: It destabilizes other molecules

When a phosphate group is released from ATP, the correct understanding involves the hydrolysis of ATP, which typically involves the breakage of one of the high-energy phosphate bonds. The release of this phosphate group results in the transformation of ATP into ADP (adenosine diphosphate) and an inorganic phosphate. This process is significant for cellular activities. The release of the phosphate group leads to a decrease in energy associated with the molecule, as ATP is known for its high-energy state due to the repulsion of negatively charged phosphate groups. By losing a phosphate, the molecule becomes more stable, which in turn provides energy that can be used to drive other biochemical reactions within the cell. This release can create a more destabilized state for other molecules that are involved in coupling the energy released to do work in the cell, such as muscle contraction, active transport, and other metabolic processes. This interplay of stabilization and energy transfer illustrates how the release of a phosphate group from ATP is critical for the driving of endergonic reactions, supporting cellular metabolism and function. Therefore, the mechanism of ATP hydrolysis is fundamental to understanding energy flow within biological systems, emphasizing how the release of a phosphate group is more about facilitating exergonic reactions and not necessarily about destabil