What are formed when the plasma membrane surrounds a particle outside of the cell?

When the plasma membrane surrounds a particle outside of the cell, it creates endocytic vesicles through a process known as endocytosis. This process allows the cell to take in materials from its external environment. During endocytosis, the membrane engulfs the particle, eventually pinching off to form a vesicle that can then transport the enclosed material into the cell for processing or digestion.

Endocytic vesicles are essential for various cellular functions, including nutrient uptake, receptor recycling, and defense against pathogens. The formation of these vesicles is crucial for maintaining cellular homeostasis and allowing cells to interact with their environment effectively. This is why the correct answer pertains specifically to endocytic vesicles, as they are directly involved in encapsulating external particles through the action of the plasma membrane.