The early endosome is a dynamic organelle that functions as the main sorting station and determines the fate of any incoming macromolecule which enters a cell in an endocytic vesicle. Transferrin – a protein that facilitates iron uptake in the cell enters through this pathway. Transferrin binds to iron, forming a complex called ferrotransferrin. Once ferrotransferrin binds to its receptor present on the cell surface, it is internalized by receptor-mediated endocytosis. The endocytosed vesicle, containing the ferrotransferrin-receptor complex, loses its clathrin coating and fuses with the early endosome. Then, the acidic environment of the early endosome causes iron to be released from transferrin . The released iron exits through a channel and later can be incorporated into hemoglobin or bind to iron-storage proteins, such as ferritin. The iron-free transferrin, also known as apotransferrin, remains bound to its receptor. The apotransferrin-receptor complex enters the early endosome's tubular domain, from where it is recycled back to the plasma membrane. Once outside the cell, apotransferrin detaches from its receptor to bind to more incoming iron.