Final answer:
To make ATP, an endergonic reaction is required that is powered by the energy released from the hydrolysis of ATP to ADP and inorganic phosphate through a process known as energy coupling.
Step-by-step explanation:
To overcome the energy barrier, or energy required, to make ATP, cells need to conduct an endergonic reaction. This type of reaction requires an input of energy because the products of the reaction have more free energy than the reactants. The energy for these reactions within cells is often supplied by breaking down an energy-rich molecule, adenosine triphosphate (ATP). ATP contains high-energy phosphate bonds that, when broken, release a burst of energy which can be harnessed to perform cellular work and overcome the activation energy barrier. This process is a part of energy coupling, where the exergonic reaction of ATP hydrolysis drives an endergonic reaction, effectively enabling the synthesis of ATP from ADP and inorganic phosphate (Pi).