Endocytosis - Types of Endocytosis - Pinocytosis, Phagocytosis, Receptor Mediated Endocytosis

Endocytosis:

It is a process by which cells cab take in material from the extracellular environment. Endocytosis involves the cell membrane invaginating and engulfing the material into the cell. The intake of bulk material from surrounding into the cell through a membrane bound vesicle.

There are 3 different types of endocytosis:

1. Pinocytosis
2. Phagocytosis
3. Receptor Mediated Endocytosis

Pinocytosis:

This is also known as cell-drinking. The cell uses the invagination to take in the surrounding bulk liquid or the aqueous media along with the dissolved solutes through the membrane bound vesicle into the cell. The vesicles of pinocytosis is relatively small.

Through the process of pinocytosis, cell gets nutrients and cell signalling components.

Liver cells, Kidney cells and epithelial cells most commonly uses pinocytosis.

Phagocytosis:

This is also known as cell eating. Cell uses pseudopodia to engulf large materials. These include bacteria, dead cells, etc.

Psuedopodia brings in engulfed material through membrane bound vesicles. The vesicles in phagocytosis are large compared to the vesicles of pinocytosis.

Phagocytosis process is very common to different cells of the immune system, these are macrophages, dendritic cells, neutrophils, etc. Once the bacteria is engulfed, immune system then process these vesicles.

Receptor mediated Endocytosis:

This is the most specific type of endocytotic process. It involves the ingestion of macromolecules such as sugars and hormones bind to receptor proteins on the cell membrane. This binding doe not only signal invagination but also the formation of protein coat around the vesicle. The vesicle is known as clathrin coated vesicle.

The main purpose is to ingest the macromolecules that bind to the receptor.