Digestion of Pinocytotic and Phagocytic Foreign Substances Inside the Cell — Function of the Lysosomes Almost immediately after a pinocytotic or phagocytic vesicle appears inside a cell, one or more
lysosomes become attached to the vesicle and empty their acid hydrolases to the inside of the vesicle,
as shown in Figure 2-12. Thus, a digestive vesicle is formed insidethe cell cytoplasm in which the
vesicular hydrolases begin hydrolyzing the proteins, carbohydrates, lipids, amino acids, glucose,
phosphates, and so forth that can diffuse through the membrane of the vesicle into the cytoplasm. What
is left of the digestive vesicle, called the residual body, represents indigestible substances. In most
instances, this is finally excreted through the cell membrane by a process called exocytosis, which is
essentially the opposite of endocytosis. Thus, the pinocytotic and phagocytic vesicles containing
lysosomes can be called the digestive organs of the cells.
Synthesis and Formation of Cellular Structures by Endoplasmic Reticulum and