LAUSR

The plasma membrane insulates a cell from its outside environment, serving as a selectively impermeable barrier across which only small or hydrophobic molecules can pass. Although the membrane is necessary for life, it is also problematic when useful macromolecules such as antibodies, peptides, polysaccharides, and imaging agents are blocked from entry. Most macromolecules can easily be uptaken by the cell through endocytosis, but remain trapped and eventually degraded within endosomes, which mature into lysosomes.