Final answer:
The triskelion molecule that forms the coats on vesicles for receptor-mediated endocytosis is clathrin. It helps in forming coated pits on the cell surface, which invaginate to internalize specific substances into the cell, and post-internalization, the vesicle membranes without clathrin are recycled.option 1 is correct answer.
Step-by-step explanation:
The molecule known as the triskelion molecule, which forms the coats on vesicles associated with receptor-mediated endocytosis, is clathrin. Clathrin plays a critical role in the formation of coated pits on the cell membrane that are involved in this specialized form of endocytosis. These coated pits are responsible for the selective internalization of various substances into a cell. During receptor-mediated endocytosis, extracellular substances first bind to receptors on the cell surface. Then, these receptors aggregate and form coated pits with the help of clathrin.
As these pits invaginate and eventually pinch off from the membrane, they form clathrin-coated vesicles which carry the internalized substances into the cell. Post-delivery of their contents, the vesicle membranes, now without the clathrin coat, are recycled back to the plasma membrane.
Clathrin's function is distinct from other proteins involved in vesicle formation and transport such as COPI, COPII, and SNARE proteins. Clathrin, along with adaptor protein 1 (AP1) and other associated proteins, specifically recruits cargo for entry into the cell, making it the key component for recognizing and trapping the particular substances targeted for uptake. Following internalization, clathrin is released from the vesicle, which then merges with an early endosome to initiate content sorting and the eventual recycling of certain components, such as receptors, to the cell membrane.