Enzyme-linked receptors are a type of cell surface receptor that, upon binding to a specific ligand, activate their intrinsic enzymatic activity or associate with other enzymes. This process typically leads to a cascade of biochemical reactions within the cell, often involving the addition of phosphate groups to proteins, a process known as phosphorylation. These receptors play crucial roles in various cellular functions, including growth, differentiation, and metabolism. Common examples of enzyme-linked receptors include the insulin receptor and epidermal growth factor receptor (EGFR), both of which are vital for regulating cellular responses to external signals.