Final answer:
Receptor-mediated endocytosis is a selective process where specific extracellular macromolecules are internalized by binding to receptors that aggregate in coated pits on the cell surface, forming vesicles that enter the cell.
Step-by-step explanation:
In receptor-mediated endocytosis, specific extracellular macromolecules are internalized into the cell through a highly selective process. This mechanism involves extracellular substances binding to receptors that are located on the cell surface. Once bound, these receptors aggregate in specialized areas known as coated pits. These coated pits invaginate to form a vesicle that engulfs the bound substances.
The vesicle, typically a clathrin-coated vesicle, then pinches off from the cell membrane and is transported into the interior of the cell. This method is not only highly efficient but also allows for the selective uptake of macromolecules, which can include hormones, cholesterol, iron, and other important substances.