Briefly describe pinocytosis and phagocytosis. Differentiate between the two.

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Solution

Pinocytosis Phagocytosis
It is the bulk intake of fluid materials by a cell.
It is the intake of solid material from outside to the inside of the cell.
Vesicles formed in pinocytosis are small.
Vesicles formed in phagocytosis are large.
Membrane possesses receptor pits for receiving the materials.
Receptor pits are absent.
Membrane does not show evagination during pinocytosis.
Membrane evaginates on the periphery to engulf the solid particle.
Digestion or breakdown of absorbed substances may or may not occur. Accordingly a food vacuole may or may not be formed.
A digestive or food vacuole is formed from a phagosome.
Lysosomes play no role in utilization of absorbed materials if digestion is not involved.
Lysosomes are essential because solid substances taken in by phagocytosis require digestion.
There is no exocytosis or ephagy.
The undigested parts of the solid particle are thrown out by exocytosis or ephagy.
The intake of materials in the form of carrier vesicles formed by invagination of small regions of plasma membrane is known as endocytosis. It 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.

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