This must be removed before the phagosome can fuse with a lysosome. Mycobacteria taken into a phagosome are able, in some way, to keep the TACO coat from being removed. Thus there is no fusion with lysosomes and the mycobacteria can continue to live in this protected intracellular location. But endocytosis also provides a much more elegant method for cells to pick up critical components of the ECF that may be in scant supply. For example, iron is transported in the blood complexed to a protein called transferrin .
Cells have receptors for transferrin on their surface.
When these receptors encounter a molecule of transferrin, they bind tightly to it. The complex of transferrin and its receptor is then engulfed by endocytosis. Ultimately, the iron is released into the cytosol . Receptor-mediated endocytosis is many thousand times more efficient that simple pinocytosis is enabling the cell to acquire the macromolecules it needs. Receptor Cells take up cholesterol by receptor-mediated endocytosis.