Biology

Difference between exocytosis and endocytosis

Main difference

The main difference between exocytosis and endocytosis is that in exocytosis the content is released outside the membrane, while in endocytosis the content is wrapped inside the membrane.

Exocytosis versus endocytosis

Word exocytosis is a combination of two words; one is “Exo” means “external” and “cytosis” means “transport mechanism.” The word endocytosis is also a combination of two words; one is “endo” means “internal” and the other is “cytosis” means “transport mechanism.” The term exocytosis means “to excrete waste out of the cell.” The term endocytosis is defined as “the capture of food particles by enveloping them from outside the cellular environment. «

In exocytosis, the vesicle fuses with the plasma membrane to excrete the material. In endocytosis, a vesicle forms around the food particle for easy swallowing. The exocytosis process is used for different purposes such as neurotransmitters, expelling cellular or chemical wastes, releasing hormones, glucose and proteins at the time of need in other parts of the body. However, the endocytosis process is used for the purpose of receiving nutrients, signal receptors, cell migration, cell adhesion, and at the time of entry of pathogens.

The secretion of proteins outside the cell is an example of exocytosis. The absorption of bacteria by neutrophils is an example of endocytosis. In exocytosis, mainly the vesicles constructed from the Golgi apparatus that contain proteins for elimination outside the cell and some vesicles contain other waste material. In endocytosis, the cell wall invaginated and created a pocket around the particle, which is pinched with special proteins, leaving the particle with a vesicle inside the cell. The main function of exocytosis is the elimination of waste. The important function of endocytosis is to absorb nutrients.

Comparative chart
Exocytosis Endocytosis
Eliminating waste to the external environment is exocytosis The intake of substances from the external environment is endocytosis.
Vesicles involve
Secretory vesicles Phagosomes
Follow, continue
Regulated secretory pathways Pinocytosis
Refers to
Exporting Having in
Examples
Release of hormones Bacteria envelopment

What is exocytosis?

Exocytosis is the process of expelling oversized particles through the cell membrane. To excrete waste and other chemicals, a vesicle forms that surrounds them. However, on some occasions, the vesicle is made up of the membrane of the molecule. This vesicle swallowed the molecule and pushed it towards the edge of the cell membrane from where it exits the cell membrane. The vesicle fuses with the membrane to release waste contents out of the cell. When a cell is ready to get rid of the toxin substance and export, excess protein exocytosis occurs. The new protein and lipid molecules that are produced move to the top of the plasma membrane.

Waste material from the Golgi apparatus that is exported out of the cell with the help of secretory vesicles is an example of exocytosis. These secretory vesicles move towards the plasma membrane to release the external environment. The hormones from our digestive enzymes have also followed the exocytosis process. Because the vesicle contains a large amount of debris, they are also known as ‘dense core vesicles’. The exocytosis process is carried out separately by different molecular components like exosomes, lysosomes, endosomes, etc.

Secretory pathways of exocytosis
  • Constitutive secretory pathway : This pathway is used to secrete peptides. Some molecules, such as histamine and other enzymes, also followed this path. Some secretory proteins are also destined for this type of pathway.
  • Regulated secretory pathway : this type of pathway is regulated by the soluble stimulant. Ligands are needed to bind to receptors on the cell membrane that are necessary for this pathway.

What is endocytosis?

Endocytosis is the process of those molecules that are too large and cannot simply cross the plasma membrane. So in this situation, the membrane envelops the protein molecule from the closest point of the plasma membrane by the process of endocytosis. After swallowing the molecule or protein, there are some receptors on the plasma membrane to which these molecules adhere to facilitate their transport. When the molecule approaches the plasma membrane, the membrane is pinched and forms a sac or vesicle that surrounds the molecule and moves it directly to the cytosol.

By endocytosis, a substance is captured from the outside by the folds of the membrane around the substance to form a membrane-bounded sac and finally pushed into the cell. The vacuole that forms to take up matter in the living cell is also known as the “endocytic vacuole.” The endocytic vacuole surrounded the contents. The endocytosis process is followed mainly by eukaryotic cells.

Types

  • Phagocytosis: The term phagocytosis is also known as “cell feeding.” It involves the absorption of solid material through the formation of phagocytic vesicles. Phagocytic activity is mainly shown in single-celled eukaryotes, eg Amoeba. Amoeba follows the process of phagocytosis to engulf food material. This process is also followed to engulf bacteria, debris and viruses, and other cells. Macrophages and some neutrophils are the best examples of phagocytes.
  • Pinocytosis: The term pinocytosis is also known as “cellular drink.” It involves wrapping a dissolved substance or liquid material around a pinocytic vesicle.
Key differences
  1. Exocytosis is related to waste discharge, while endocytosis is related to nutrient absorption.
  2. Exocytosis has to do with release; on the other hand, endocytosis is about capturing.
  3. In exocytosis, the vesicle fuses with the cell membrane, conversely, in endocytosis, the vesicle does not fuse.
  4. The decomposition of the gallbladder by exocytosis on the other side, endocytosis builds the gallbladder.
  5. Exocytosis involves the formation of a cell wall, whereas endocytosis does not involve the formation of a cell wall.
  6. Exocytosis uses vesicles to remove material, although endocytosis uses vesicles to transport food particles.
  7. Exocytosis increases the size of the plasma membrane compared to endocytosis and the size does not increase.
  8. In exocytosis, a vesicle forms around the Golgi apparatus. However, an endocytosis vesicle forms around the contents.
  9. Exocytosis is transport out of the cell; on the other hand, endocytosis is transport within the cell.

Final Thought

It is concluded that exocytosis is the outward movement of the material and endocytosis is the inward movement of the material.

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