Phagocytosis vs Pinocytosis
Intake of many macromolecules and other suspended particles including cell parts, macromolecular aggregates, and foreign particles is usually done by a mechanism called endocytosis. The opposite action of endocytosis is exocytosis, by which the substances are moved away from the cell using a mechanism, which is similar to endocytosis. Exocytosis is commonly seen in secretory cells. Based on the nature of the particles that are taken into living cells, there are two types of endocytic mechanisms, namely; phagocytosis and pinocytosis. The same mechanism is used in both cases, where plasma membrane invaginates to form vesicles called endosomes, in which the engulfed material is located. In both cases, the engulfed materials are surrounded by plasma membrane. Phagocytosis and pinocytosis are considered as active processes that utilize ATP to intake materials. Because of this reason, mitochondria can be seen near the surfaces where these processes occur.
What is Phagocytosis?
Phagocytosis is the intake of solid particles larger than about 0.5µm in diameter through endocytosis. Phagocytosis is often called cell eating. In this case, plasma membrane fuses forward and surrounds the particles near the cell surface to form phagocytic vesicles called phagosomes. Lysosomes then come and fuse with these phagosomes and release their digestive enzymes to digest the content in phagosomes. Phagocytosis is a process by which most protozoan including amoeba, engulf and digest their prey. In higher animals, this process is used by neutrophils and macrophages of the immune system to defend against foreign bodies such as bacteria, virus, dust particles, dead cell, cellular parts and other waste matter.
What is Pinocytosis?
Pinocytosis is the active intake of droplets of extracellular fluid along with small particles. Because of the nature of material involved in pinocytosis, it is often called cell drinking. It helps to intake important solutes such as insulin and lipoproteins in concentrated form. Additionally, ions, sugars and amino acids also enter the cell by this method. In this case, first extracellular fluid with minute particles adheres to specific receptors located on the cell membrane. Then the plasma membrane of that particular area invaginates and surrounds the particles to form membrane bounded vesicles called pinosomes. The pinosomes then move into the cytoplasm, and the content is released. Pinocytosis can be seen very often in the cells that line the blood capillaries.
What is the difference between Phagocytosis and Pinocytosis?
• Phagocytosis is the intake of solid particles larger than about 0.5µm in diameter, whereas pinocytosis is the intake of droplets of extracellular fluid along with small particles.
• Phagocytosis is generally used for defensive purposes, whereas pinocytosis is used to intake important materials into cells.
• Phagocytosis forms vesicles called phagosomes, whereas pinocytosis forms vesicles called pinosomes.
• Unlike in the pinocytosis, involvement of lysosomes can be seen in phagocytosis.
• In phagocytosis, solid particles such as bacteria, dust, cellular parts, cells are taken into cells, while in pinocytosis, ions, sugars, amino acids etc., are taken into cells.
• Phagocytosis is also known as cell eating, whereas pinocytosis is known as cell drinking.
• Pinocytosis often occurs in the cell lining of blood capillaries, whereas phagocytosis is used by white blood cells such as neutrophils and macrophages, and protozoan.