See Becker fig. Need specific receptor for each substance transporte d 2 . Concentrates substance transported 3 . Clathrin is coat protein for vesicles forming from plasma membrane and trans-Golgi. Exocytosis balances endocytosis so cell surface area stays the same.
Material can remain inside a vesicle or outside cell at all times.
Click here for animation. Membrane starts to invaginate to form coated vesicle . A single vesicle can contain more than one type of receptor plus ligand. Uncoated, acidified vesicle can be called an endosome, early endosome, or sorting vesicle. Acidification requires energy for proton pump.