Final answer:
Receptor-mediated endocytosis is a selective process where the cell's membrane receptors specifically bind and internalize certain substances, unlike phagocytosis, which is nonselective and ingests large particles.
Step-by-step explanation:
The key difference between receptor-mediated endocytosis and phagocytosis lies in the specificity and mechanism by which substances are taken up by the cell. Receptor-mediated endocytosis is a highly selective process that involves the cell membrane containing specific receptors for a certain substance. When these surface receptors bind enough of the specific substance, or ligand, the cell then endocytoses the membrane section containing the receptor-ligand complexes. This is different from phagocytosis, which is a relatively nonselective process where the cell engulfs large particles.
For example, red blood cells utilize receptor-mediated endocytosis to take in iron, which is essential for hemoglobin. Iron in the bloodstream is bound to a protein called transferrin, which is recognized and bound by specific transferrin receptors on the surface of red blood cells, prompting the endocytosis of these iron-transferrin complexes.