Phagocytosis

When you’re reading the word “phagocytosis” you may be struggling to understand what it means, but the important thing to focus on is what the process actually is – when cells ingest solid matter particles. The particles that the cell has ingested can either be of nutritional value or they can be bacterial particles.

Simplified illustration of the stages of phagocytosis
Simplified illustration of the stages of phagocytosis

Specialized cells

There is a certain type of cell that can perform this process, the phagocyte. They go through what is called the phagocytosis process to do this. There are different types of cells that fit into the phagocyte category which include the amoeba, or a cell that is part of a whole body of a multi-cellular being.

Cells ingesting solid matter

The act of phagocytosis falls under a grouping of processes titled endocytosis. All of the processes that fall under this category refer to a process in which a cell ingests material for whatever reason like nutritional or bacterial.

Animation: example phagocytosis
Animation: example phagocytosis

The process of phagocytosis

The process of phagocytosis may seem overly complicated, but it’s fairly basic when you break it down into smaller parts. In the process, the end goal is to internalize solid particles like bacteria. While the process of phagocytosis is clumped in the endocytosis category, it is different from other processes in this grouping, which often entail the ingestion of liquids versus solids.

Liquid and solid absorption

There are unicellular bodies, like protists, that use endocytosis processes for feeding, but through liquid. This is actually a method that can account for all of their nourishment. When a unicellular organism uses phagocytosis to gain all of their nutrition, a process called phagotrophic nutrition occurs.

Animation: example phagocytosis
Animation: example phagocytosis

The amoeba

An example of an organism that uses phagocytosis is the amoeba. The amoeba uses its pseudopod (temporary projections of the cell wall that can “grab” objects or help the amoeba to “walk”) and completely engulfs the source of the nutrients. When ciliates perform this act, they use cytosomes to complete the phagocytosis process.

Our immune system cells

Other examples of organisms that use phagocytosis to feed are immune system cells, and they use the process to kill bad organisms and materials in the body to help to protect their host. Many mammals have these phagocyte immune cells in their bodies to get rid of bad bacteria and infections. When this process happens in mammals, the cell membrane will expand in the cell of their phagocyte, so it can grow large enough to ingest the particles.

Steps of Phagocytosis

The only way to see the process of phagocytosis is under a microscope, and this can actually be pretty fascinating. But phagocytosis isn’t one spontaneous process. It is the culmination of several steps that you can detect when observing the process.

Step 1

The phagocyte cells, which were previously inactive, become activated because of chemical signals from the nutrient particles around them. Once they’ve been activated, they produce receptors called surface glycoprotein receptors that make it easier for the organism to take grip on the particles.

Step 2

Once this occurs, the phagocyte will move slowly and use the newly produced receptors to attach itself to the particle it is trying to ingest. Upon being attached, the phagocyte cell starts to expand, forming a large cone around the particles.

Step 3

Once the cell membrane of the cell has surrounded the particle, it goes through the process of making a vacuole, also known as a food vacuole. Once the vacuole is complete, then the phagocyte will pull the particle inside, so it can be absorbed.

Step 4

The last step involves lysosomes, which have the role of digesting the food particles through the cell membrane. When the lysosomes break down the particles, they will be able to absorb the nutrients into the cell, while also getting ride of particle waste. When this final step is completed, within immune cell systems, the cell will create a peroxisome to help to dispose of the toxins.

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