What is the mechanism of receptor-mediated endocytosis?

Receptor-mediated endocytosis is a highly specialized process where the interaction between a specific receptor on the cell membrane and its corresponding ligand triggers the internalization of molecules into the cell. This mechanism allows cells to selectively uptake specific substances, such as nutrients, hormones, or other signaling molecules, that they need for various functions.

When a ligand binds to its receptor, the receptor-ligand complex triggers the invagination of the membrane, leading to the formation of a vesicle that brings the desired molecules into the cell. Because this process is selective and involves specific receptors, it is efficient in regulating what enters the cell compared to other methods of endocytosis that may not provide such specificity.

The other options do not accurately describe receptor-mediated endocytosis, highlighting the unique focus of this mechanism on receptor-ligand interactions, the requirement for energy in forming vesicles, and its specificity for certain types of molecules, rather than a general or passive uptake of any and all substances.