Final answer:
The free energy released by the hydrolysis of ATP is used for endergonic reactions within the cell, powering cellular processes such as the Na+/K+ pump for ion transport, muscle contraction, and the synthesis of macromolecules.
Step-by-step explanation:
When ATP is hydrolyzed, it is converted into ADP and inorganic phosphate, and free energy is released. This energy is used for various cellular processes that require energy inputs; these processes are known as endergonic reactions. The energy from ATP hydrolysis often powers the synthesis of macromolecules, muscle contraction, active transport across cell membranes, and other forms of cellular work. A particular instance of this is the action of the Na+/K+ pump, where ATP hydrolysis provides the energy needed to change the pump's shape, allowing it to transport sodium and potassium ions across the cell membrane.
In this critical process, the gamma phosphate of ATP doesn't just drift away when hydrolyzed, but is instead transferred onto the pump protein in a process known as phosphorylation. This phosphorylation leads to a conformational change in the pump that promotes the movement of ions. Hence, ATP hydrolysis facilitates the coupling of an exergonic reaction (the release of energy from ATP) with endergonic reactions (such as those required to drive the Na+/K+ pump), permitting them to proceed and perform cellular work.