How do cells internalize molecules and other cells?
This figure diagrams the major internalization events. In the two views on the right, receptors are not needed for internalization. During phagocytosis, cells may simply internalize particles or cells, like bacteria (cell eating). In the second, called pinocytosis, cells internalize soluble material (cell drinking). In both types of internalization, the cells extend processes and bring cells or soluble material into the cell in a vacuole. In the presentation on lysosomes , we learned that the vacuole formed in the cell by phagocytosis or pinocytosis often became a lysosome after hydrolases were brought to it and the pH was adjusted. The vacuoles formed are called phagosomes or macropinosomes. This cartoon was taken from Endocytosis, Edited by Ira Pastan and Mark C. Willingham, Plenum Press, N.Y., 1985 Endosomes are formed by receptor-mediated endocytosis. In this case, cells bring in proteins and other types of ligands attached to the plasma membrane via receptors. The process depends
