What is the primary energy currency of the cell?

The primary energy currency of the cell is ATP (adenosine triphosphate). ATP is a molecule that stores and transports chemical energy within cells for metabolism. It is fundamental for powering various cellular processes, including muscle contraction, active transport across cell membranes, and biosynthetic reactions.

ATP consists of three phosphate groups, and when energy is needed by the cell, it can release energy by breaking the high-energy phosphate bond, converting ATP into ADP (adenosine diphosphate) and an inorganic phosphate. This process is essential for energy transfer and is vital for maintaining the cell's energy balance.

In contrast, ADP is a less energetic molecule, as it has only two phosphate groups. NADH and FADH2 are carriers of electrons used in metabolic pathways, particularly in cellular respiration, but they do not serve as the direct energy currency for cellular processes the way ATP does. Therefore, ATP is recognized as the primary energy currency of the cell.