Final answer:
A coupled reaction in metabolism uses energy from an exergonic reaction to power an endergonic reaction, such as the ATP breakdown providing energy for cellular processes.
Step-by-step explanation:
A metabolic reaction that involves one reaction releasing energy to provide energy for a second reaction that requires energy is known as a coupled reaction. This occurs when the energy from an exergonic reaction (energy-releasing, catabolic process) is used to drive an endergonic reaction (energy-consuming, anabolic process). An example of this in cellular metabolism is when the breakdown of adenosine triphosphate (ATP) releases energy that is then used to power various cellular activities that require energy.