The molecule commonly referred to as the "energy currency" of the cell is adenosine triphosphate (ATP). ATP stores and transfers energy within cells, making it crucial for various cellular processes, including metabolism, muscle contraction, and active transport. When energy is needed, ATP releases one of its phosphate groups, transforming into adenosine diphosphate (ADP) and releasing energy for cellular activities. This mechanism underpins the energetic transactions that sustain life at the cellular level.