Endocytosis and exocytosis

The endocytosis is the transport of particles and substances inside the cell, while the exocytosis is intracellular transporting material outward. Both processes are due to the cell’s need to maintain an exchange of materials with its environment for its survival.

Both endocytosis and exocytosis are mechanisms involved in the transport of materials across the plasma membrane. This is a type of active mass transport that requires energy in the form of ATP.

EndocitosisExocytosis
DefinitionCellular mechanism to trap substances from the extracellular environment.Cellular mechanism to release or export content to the extracellular medium.
ProcessThe plasma membrane envelops and surrounds the substance.Intracellular vesicles fuse with the plasma membrane.
TypesPhagocytosis (solid material) and pinocytosis (liquid material).Constitutive secretory pathway and regulated secretory pathway.
Vesicle formationInternal endocytic vesicles, called phagosomes, formSecretory vesicles form in the Golgi apparatus.
ExampleA white blood cell ingesting a bacteria.Endocrine cells release hormones by exocytosis.

What is endocytosis?

Endocytosis is the process by which cells capture material from the extracellular environment . In this process, the material to be ingested progressively closes in a small portion of the plasma membrane, which is introduced or invaginates inside the cell, to finally separate from the membrane and form an endocytic vesicle.

Cells use endocytosis to trap nutrients, such as vitamins, cholesterol, and iron. Depending on the size and consistency of the material to be ingested, there are two types of endocytosis: phagocytosis and pinocytosis.

Phagocytosis

Phagocytosis is the endocytosis of large, solid particles. Another way of looking at the process of phagocytosis is as “the cell eating.” One example is single-celled organisms, such as amoebae, which resort to phagocytosis for food.

In higher multicellular organisms, there are cells known as “professional phagocytes”, such as white blood cells or leukocytes and macrophages. These cells are responsible for defending the body against invading agents, such as bacteria, viruses and parasites.

The vesicle resulting from phagocytosis is called a phagosome. These phagosomes fuse with lysosomes, which are the intracellular organelles responsible for the digestion of the material.

Pinocytosis

Pinocytosis is the internalization of dissolved molecules in a fluid. Pinocytosis can be translated as “the cell drinking.”

What is exocytosis?

Exocytosis is the cellular process to release material to the outside. It is the reverse process of endocytosis. From the Golgi apparatus, vesicles destined to fuse with the plasma membrane are formed. Two pathways for exocytic secretion are distinguished: constitutive and regulated.

Constitutive secretory pathway

In this way, the vesicles fuse with the plasma membrane continuously. This is how the cell removes waste.

Regulated secretory pathway

To activate this pathway, some special signal is required within the cell that tells it to release the products into its secretory vesicles. This pathway is mainly found in cells specialized in secreting products, such as neurons, which release neurotransmitters, or endocrine cells, which release hormones.

Learn more about Eukaryotic cell and prokaryotic cell .

What is transcytosis?

In some cells, such as endothelial cells, material is transported from one side of the cell to the other. This process is known as transcytosis.

In transcytosis, endocytosis (capture of material from outside) and exocytosis (release of material into the extracellular space) complement each other.

You may also be interested in Active and passive cellular transport

Comparison table between endocytosis and exocytosis

Add a Comment

Your email address will not be published. Required fields are marked *