Question

Explain the three types of endocytosis

Answer 1

Endocytosis is a process where eukaryotic cell internalise material from surrounding emvironment.Internalisation is achieved by the formation of membrane bound vesicle derived by invagination and pinching off of pieces of plasma membrane in a process termed endocytisis.

It is of three types :

1) Phagocytosis: It is also known as cell eating.It is the internalisation of large particles following particle binding to specific plasma membrane receptors and by the formation of large endocytic vesicle called phagosome.The phagosome fuses with lysosome to form phagolysosome.

2) Pinocytosis: It is also known as cell drinking.It involves the ingestion of fluid by the formation of small endocytic vesicle of about 100 nm in diameter.Virtually all eukaryotic cell perform pinocytosis.Uptake of soluble material dissolved in extracellular fluid during pinocytosis occur both selectively and non selectively.

3) Receptor mediated endocytosis: In this type of endocytosis a specific receptor on the cell surface binds tightly to the extracellular macromolecule that it recognizes.The plasma membrane region containing the receptor ligand complex then undergoes endocytosis, becoming a transport vesicle.Receptor ligand complexes are selectively incorporated into intracellular transport vesicles.