What is the Difference Between Phagocytosis and Receptor-Mediated Endocytosis

The main difference between phagocytosis and receptor-mediated endocytosis (or clathrin-mediated endocytosis) is that phagocytosis is the intake of large food particles by the plasma membrane of the cell whereas receptor-mediated endocytosis is the uptake of large particles by the cell membrane with the help of receptor proteins.

Phagocytosis and receptor-mediated endocytosis are two pathways that help the cells uptake large particles. Phagocytosis forms phagosomes while receptor-mediated endocytosis forms vesicles and surrounding particles.  

Key Areas Covered

1. What is Phagocytosis
   • Definition, Characteristics, Importance
2. What is Receptor-Mediated Endocytosis
   • Definition, Characteristics, Importance
3. Similarities Between Phagocytosis and Receptor-Mediated Endocytosis
   • Outline of Common Features
4. Difference Between Phagocytosis and Receptor-Mediated Endocytosis
   • Comparison of Key Differences

Key Terms

Phagocytosis, Receptor-Mediated Endocytosis, Clathrin-mediated Endocytosis

What is Phagocytosis

Phagocytosis is the process in cells that use plasma membrane to engulf large particles, which are more than 0.5 μm. During phagocytosis, the cell takes up particles like cell debris, aged cells, small mineral particles, dust, various colloids, and bacteria. The immune system cells like tissue macrophages, neutrophils, and monocytes use phagocytosis to engulf cells. Phagocytic cells also occur in Langerhans cells in the skin, Kupffer cells in the liver, the pigmented epithelium of the eye, and the microglia in the brain. Phagocytosis is important in defense mechanisms that destroy pathogenic material found in the body. It is also a receptor-mediated process. Some of the receptors important in this process are immunoglobulin G, mannose (MR), β-glucan, and complement (CR1, CR3).

Figure 1: Phagocytosis

Furthermore, surrounding the particle to be uptaken the phagocytic cells form pseudopodia. Then, the plasma membrane is pinched off into a phagocytic vesicle or a phagosome. Phagosomes are capable of fusing with lysosomes, forming the phagolysosomes. Moreover, the enzymes inside the phagolysosome help to digest the materials inside the phagosome. After digestion, the waste materials eliminate through exocytosis. Phagocytosis is a cell-eating mechanism.

What is Receptor-Mediated Endocytosis

Receptor-mediated endocytosis or clathrin-mediated endocytosis is a process of absorbing metabolites, hormones, proteins, and sometimes viruses by inward budding of the plasma membrane. Therefore, it is important in importing macromolecules from the extracellular fluid. However, the main feature of this process is the receptors strictly mediating the substances the cell absorbs. Some receptors internalize continuously while some receptors undergo internalization by the formation of vesicles after binding them to ligands.

Figure 2: Receptor-mediated Endocytosis

Moreover, in receptor-mediated endocytosis, the receptors slide laterally into coated pits that are invaginated regions of the plasma membrane surrounded by clathrin and pinch off to form clathrin-coated vesicles. Endosome is the immediate destination of these vesicles. Generally, these vesicles bind to a lysosome to recycle.

Similarities Between Phagocytosis and Receptor-Mediated Endocytosis

• Phagocytosis and receptor-mediated endocytosis are two cellular mechanisms for the uptake of large particles.
• Moreover, both processes occur through the invagination of the plasma membrane.
• Finally, both types of invaginated vesicles bind with lysosomes to undergo digestion.

Difference Between Phagocytosis and Receptor-Mediated Endocytosis

Definition

Phagocytosis refers to the ingestion of bacteria or other material by phagocytes and amoeboid protozoans, while receptor-mediated endocytosis refers to one of the most important processes with which viruses and bioparticles can enter or leave an animal cell.

Formation of Vesicles

Phagocytosis forms a phagosome while receptor-mediated endocytosis forms an endosome.

Importance

Generally, phagocytosis engulfs food particles and is important in immunity to engulf infected cells. Meanwhile, receptor-mediated endocytosis is important in engulfing macromolecules from the extracellular fluid.  

Conclusion

Phagocytosis involves the engulfing of food particles by protozoa and infected cells by immune system cells such as macrophages, while receptor-mediated endocytosis involves engulfing macromolecules through clathrin-mediated vesicles. Therefore, this is the main difference between phagocytosis and receptor-mediated endocytosis. In brief, these are two mechanisms of cells to engulf large particles from the cell surroundings. 

References:

1. Wikimedia Foundation. (2022, July 14). Phagocytosis. Wikipedia. Retrieved September 21, 2022.
2. Receptor-mediated endocytosis. Receptor-Mediated Endocytosis – an overview | ScienceDirect Topics. (n.d.). Retrieved September 21, 2022.

Image Courtesy:

1. “0309 Phagocyotsis” By OpenStax – Own work (CC BY 3.0) via Commons Wikimedia
2. “Itrafig2” By Grant, B. D. and Sato, M – Own Work (CC BY 2.5) via Commons Wikimedia