Phosphorylation is a biochemical process where a phosphate group is added to a molecule, typically a protein. This addition can change the molecule's function, activity, or location within a cell. It plays a crucial role in regulating various cellular processes, including metabolism, cell signaling, and the cell cycle. The process is often catalyzed by enzymes known as kinases, which transfer phosphate groups from high-energy molecules like ATP to target proteins. Conversely, phosphatases remove these phosphate groups, reversing the effects of phosphorylation. This dynamic balance is essential for maintaining proper cellular function and responding to environmental changes.