Question

Write a note on exocytosis and endocytosis.

Answer 1

Exocytosis: It is a process of exudating the secretory products or undigested waste products to outside of the cell cytoplasm through plasma membrane. This process is called cell vomiting or ephagy. Secretory products are packaged into transport vesicles. Transport vesicles travel to the plasma membrane from the Golgi vesicle with their cargo. At the plasma membrane, the vesicle docks and waits for a secretion signal.
Endocytosis: It involves intake of materials in the form of carrier vesicles formed by invagination of small regions of plasma membrane. Endocytosis is of two types i.e., pinocytosis and phagocytosis:

• Pinocytosis: It is also called cell drinking process, as fluid materials having high molecular weight such as proteins, amino acids, fats, insulin, lipoproteins, etc., in the form of globules enter the cytoplasm by invagination of plasma membrane. Globules of food materials are called pinosomes which are pinched off from the plasma membrane inside the cytoplasm in the form of small pinocytic vesicles.
• Phagocytosis: It is bulk intake of large sized solid particles by the cell using the plasma membrane. It is also called cell eating process. It occurs in all protozoans and in special cells of metazoans such as leucocytes of blood, the reticular cells of spleen, etc. It is pinched off from the plasma membrane inside the cytoplasm in the form of food vacuole or phagocytic vesicle. This will further be digested by lysosomes.