Final answer:
ATP, or adenosine triphosphate, is a small molecule that cells use as a primary energy currency to meet immediate energy requirements, similar to how money is used to exchange goods and services.
Step-by-step explanation:
A small, energy-carrying molecule used for a cell's immediate energy needs is called adenosine triphosphate, or ATP. ATP is vital for powering a vast majority of energy-requiring cellular reactions, including endergonic reactions which demand a significant energy input due to their products having more free energy than their reactants.
Like how currency is exchanged for goods and services, ATP can be thought of as the energy currency of the cell, providing the necessary energy to drive metabolic processes, synthesize molecules, transport substances, and perform other cellular activities.