Final answer:
Receptor-mediated endocytosis is a process where cells engulf specific molecules that bind to protein receptors on the plasma membrane. This process is selective, involving the formation of coated pits that turn into vesicles, making it different from other less selective forms of endocytosis, like phagocytosis and pinocytosis.
Step-by-step explanation:
During receptor-mediated endocytosis, molecules bind to specific protein receptors in the plasma membrane before they are engulfed by the cell. This process is highly selective and targets specific substances for cellular uptake.
Receptor-mediated endocytosis involves protein receptors that have a high affinity for certain molecules. When these molecules bind to the receptors, they cluster together in an area of the plasma membrane that forms coated pits. These pits then invaginate to create coated vesicles that contain the receptors and their bound molecules, which are then internalized by the cell.
Phagocytosis and pinocytosis are nonselective forms of endocytosis, whereas receptor-mediated endocytosis focuses on the intake of specific substances. An example is the endocytosis of iron in red blood cells, where iron bound to transferrin, a plasma protein, is taken into the cell via specific transferrin receptors in a process regulated by receptor-mediated endocytosis.