Difference Between Endocytosis and Endoreduplication

The key difference between endocytosis and endoreduplication is that endocytosis refers to the cellular process of moving substances into living cells by invagination of the cell membrane to form a vesicle while endoreduplication refers to the process of undergoing multiple S phases or multiple rounds of nuclear genome replication without entering nuclear division or mitosis.

Endocytosis and endoreduplication are two cellular processes seen in living organisms. Endocytosis helps organisms to take nutrients and other necessary substances inside the cell. Endoreduplication, on the other hand, is a mechanism which facilitates polyploidy of organisms. In endoreduplication, cells do not enter the nuclear division or cytokinesis. Instead, they undergo multiple S phases. During the multiple S phases, the genome replicates multiple times, increasing the ploidy level.

CONTENTS

1. Overview and Key Difference
2. What is Endocytosis 
3. What is Endoreduplication
4. Similarities Between Endocytosis and Endoreduplication
5. Side by Side Comparison – Endocytosis vs Endoreduplication in Tabular Form
6. Summary

What is Endocytosis?

Endocytosis is a cellular mechanism which takes substances into the interior of the cell. When substances arrive near the plasma membrane, plasma membrane surrounds and internalizes them. Then it forms a vesicle containing those materials from the inside of the cell. Endocytosis occurs in three ways: phagocytosis, pinocytosis and receptor-mediated endocytosis.

Phagocytosis is the process of taking large solid matter like cell debris, pathogens such as bacteria, dead cells, dust particles, small mineral particles, etc., into the cell by forming phagosomes. Most immune cells, including tissue macrophages, neutrophils and monocytes, use phagocytosis as a defence mechanism. Immune cells destroy pathogens by engulfing them into phagosomes and later destroying them inside the cell. A lytic action takes place inside the cell where a lysosome binds to the phagosome and forms a phagolysosome and releases lytic enzymes to destroy the engulfed pathogen or solid matter.

Pinocytosis is another form endocytosis in which extracellular fluid is taken inside the cell by forming small vesicles. Small molecules which are suspended in the extracellular fluid are transported through this mechanism. Pinocytosis does not select the molecules to transport. Whatever the small molecules present in the extracellular fluid are ingested by pinocytosis. Pinocytosis is the typical molecule transport mechanism in liver cells, kidney cells, capillary cells and epithelial cells.

Receptor-mediated endocytosis is the third form of endocytosis in which macromolecules are taken inside the cell selectively from the extracellular fluid. This mechanism is mediated by receptors located on the cell surface and their specific binding with the macromolecules outside the cell. Receptors which are involved in receptor-mediated endocytosis are concentrated in clathrin-coated pits. Extracellular macromolecules bind with receptors and internalize into clathrin-coated vesicles formed from clathrin-coated pits. The clathrin-coated vesicles then fuse with early endosomes, in which their content is sorted for transport to lysosomes or recycling to the plasma membrane.

What is Endoreduplication?

Generally, cells proliferate via mitosis. During mitosis, the cell duplicates its’ genome once. As a result, mitosis produces two genetically identical daughter cells. However, some agents interfere with this process and govern the nuclear genome replication for multiple times. In other words, some agents induce reinitiation of nuclear DNA replication during S phase (DNA re-replication). This process of undergoing multiple S phases or multiple genome duplication without entering to mitosis is known as endoreduplication or endoreplication.

In this process, the cell does not enter the mitosis phase or nuclear division. Instead, it undergoes several genome replications. In the end, it results in a giant cell with a single, enlarged, polyploid nucleus. Endoreduplication occurs as a developmentally programmed polyploidy mechanism in some organisms, especially in arthropods. When a cell undergoes endoreduplication, that particular cell exits the mitotic cell cycle in G2 phase. The cell undergoes normal Gap phases between S phases and same molecular machinery as mitotic cell cycles to regulate successive rounds of DNA replication.

Endoreduplication is widely seen in a majority of plant tissues. Moreover, it is seen in specific animal cells such as arthropod and mammalian cells.

What are the Similarities Between Endocytosis and Endoreduplication?

• Endocytosis and endoreduplication are two different cellular processes.
• Both are limited to specific cell types.

What is the Difference Between Endocytosis and Endoreduplication?

In endocytosis, cell membrane surrounds and internalizes the substances in extracellular fluid in order to take them inside the cell while in endoreduplication, the cell exits the mitosis and undergoes multiple nuclear genome replication or multiple S phases. Thus, this is the key difference between endocytosis and endoreduplication. Furthermore, these are two different cellular processes. The cell membrane plays a key role in endocytosis, which is mainly seen in immune cells. Meanwhile, the genome plays a key role in endoreduplication, which is widely seen in plant cells. Thus, this is another significant difference between endocytosis and endoreduplication. Moreover, endocytosis does not change the ploidy level of the cell, while endoreduplication increases the ploidy level of the cell.

Below infographic shows more differences between endocytosis and endoreduplication in tabular form.

Summary – Endocytosis vs Endoreduplication

Endocytosis and endoreduplication are two different processes. Endocytosis helps cells to take up nutrients and other necessary substances from the outside of the cell to inside. The cell membrane internalizes substances from the outside and takes them inside, forming a vesicle in the interior of the cell. On the other hand, endoreduplication increases polyploidy. It is widely seen in plant tissues. Moreover, it is seen in specific animal cells. In endoreduplication, the cell exits the mitosis and undergoes multiple S phases in order to replicate the genome many times. So, this summarizes the difference between endocytosis and endoreduplication.

Reference:

1. Zielke, Norman, et al. “Endoreplication.” Cold Spring Harbor Perspectives in Biology, Cold Spring Harbor Laboratory Press, 1 Jan. 2013, Available here.
2. Cooper, Geoffrey M. “Endocytosis.” The Cell: A Molecular Approach. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.

Image Courtesy:

1. “A depiction of various types of Endocytosis” By  ScienceAnimations (CC BY-SA 4.0) via Commons Wikimedia
2. “Endocycling vs. endomitosis” By Mrowe145 – Own work (CC0) via Commons Wikimedia