What molecule is known as the energy currency of the cell?

Adenosine triphosphate (ATP) is universally recognized as the energy currency of the cell because it plays a central role in cellular metabolism. ATP consists of adenosine and three phosphate groups, and its structure allows it to store and release energy efficiently. When a phosphate group is cleaved from ATP, usually through hydrolysis, a significant amount of energy is released, which can be harnessed to drive various biological processes, such as muscle contraction, nerve impulse propagation, and biosynthesis of macromolecules.

The importance of ATP arises from its ability to provide energy in a readily available form that can be used directly by enzymes and other cellular components. This rapid release of energy makes ATP indispensable in cellular functions, essentially making it the primary energy carrier that fuels many of the biochemical reactions necessary for life.

Other molecules listed, such as NADH and FADH2, serve as electron carriers and play crucial roles in cellular respiration by facilitating the transfer of electrons in metabolic pathways. While glucose is a significant energy source, it must first undergo glycolysis and other processes to produce ATP before it can be utilized for immediate energy needs. Thus, ATP's unique role as an energy currency clearly distinguishes it from these other molecules.