What molecule provides energy for cellular reactions and processes?

ATP, or adenosine triphosphate, is known as the primary energy currency of the cell. It plays a crucial role in a multitude of cellular processes, serving as a direct source of energy for biochemical reactions. When ATP is hydrolyzed, it releases energy that can be harnessed by the cell to perform work, such as muscle contraction, active transport across membranes, and the synthesis of macromolecules.

This energy release occurs when one of the phosphate groups is removed, transforming ATP into adenosine diphosphate (ADP) and an inorganic phosphate (Pi). The regeneration of ATP from ADP and Pi occurs through processes like cellular respiration and photosynthesis, highlighting its pivotal role in energy transfer.

While other molecules like NADPH and glucose also play essential roles in cellular metabolism, they do not act as the immediate energy source for cellular reactions in the same way ATP does. NADPH is primarily involved in anabolic reactions and reducing power during biosynthesis, while glucose is a primary fuel source that ultimately must be broken down through cellular respiration to produce ATP. Thus, ATP remains the molecule that directly provides the energy needed for cellular activities.