Receptor-mediated endocytosis also involves concentration of the molecules, with certain ligands binding to receptors on the cell surface and becoming concentrated before internalization.
Clathrin-mediated endocytosis is the specific uptake of large extracellular molecules, such as proteins, membrane localized receptors, and ion-channels.
Clathrin-mediated endocytosis is the major endocytoic pathway, found in all mammalian cells, and carries out the continuous uptake of essential nutrients, growth factors, antigens, and pathogens, including the cholesterol-laden, low-density lipoprotein (LDL) (Khalil et al.
Endocytosis is used by cells because most substances important to them are large polar molecules, and thus cannot pass through the hydrophobic plasma membrane.
Fluid-phase endocytosis is a low efficiency, nonspecific process that involves the bulk uptake of solutes in exact proportion to their concentration in the extracellular fluid (Khalil et al.
Three modes of endocytosis can be delineated kinetically: fluid-phase, adsorptive, and receptor-mediated endocytosis (Khalil et al.
The major and best understood route for endocytosis in most cells is that mediated by the molecule clathrin.