Phagocytosis - Definition, Steps, Process and Examples (2023)

Definition: What is Phaocytosis?

Essentially, phagocytosis may be described as a form of endocytosis through which a cell engulfs particulate matter/solid particles/cells. For different types of cells, phagocytosis plays a number of different roles ranging from food ingestion to the destruction of given cells and particulate matter.

Endocytosis definition, types and S...

Endocytosis definition, types and Steps

Some of the cells that use phagocytosis include:

  • Macrophages
  • Protozoa
  • Neutrophils
  • Epidermal cells
  • Some vascular endothelial cells

* Generally, phagocytes are divided into two major groups. These include "professional phagocytes" (white blood cells) and "non-professional phagocytes" (such cells as epithelial cells).

Phagocytosis Process

Endocytosis and Phagocytosis

Phagocytosis is the process in which a cell engulfs a particle, digests it, and expels the waste products. by Mango Slices [CC BY-SA 4.0 (]

Living cells take in different types of material across their cell membrane. For the most part, a majority of these material/molecules such as ions, fluids, and oxygen among others easily pass through the membrane through such mechanisms as ion pumps and osmosis among others.

(Video) Phagocytosis

Some of the matter, e.g. particles likeviruses, may prove too large to pass through the membrane through such mechanisms. For this reason, the cell has to engulf such matter/objects into the cell.

This process involves the invagination of thecell membranein question which allows the cell to take in the object/particle. Depending on the cell and the mechanism used to engulf such material/objects, endocytosis is divided into phagocytosis, pinocytosis and another process known as receptor-mediated endocytosis.

What differentiates phagocytosis from pinocytosis is that phagocytes posses special surface proteins that allow them to specifically identify and bind to given particles before ingesting them. This type of endocytosis is dependent on the binding between the cell and the target object/particle.

See also: Endocytosis Vs Exocytosis

Main steps of Phagocytosis

Step 1: Activation/ actuation

This step of phagocytosis occurs when the cell comes in close proximity to given objects/particles. For instance, when phagocytes are near such cells as bacteria, this activates the phagocytes and stimulates binding.

* The first step also involves chemotaxis. Here, the cells move towards the area with a high concentration of the foreign particles/cells or molecules. Cells are chemically stimulated by the presence of the foreign molecules/ particles etc.

Step 2: Binding

Here, surface receptors on the phagocyte bind/adhere to the surface of the particle. This step of phagocytosis is necessary for the molecule to be ingested.

Depending on the cell, there are different types of surface receptors that play an important role in phagocytosis (binding).

These include:

  • Scavenger receptors- Bind to various types of molecules on the surface of bacteria
  • Opsonin receptors- Opsonin receptors are some of the most studied surface receptors. They bind to molecules that possess immunoglobulin G on their surface
  • Antibodies- Some of the cells are capable of producing antibodies that make it possible to attach to certain antigens
  • Toll-like receptors- These receptors bind to specific molecules on the surface of bacteria, fungi, and viruses

* Receptor binding is an important step in phagocytosis allowing the cell to identify the object/particle/bacteria etc and thus elicit the appropriate reaction.

Step 3: Ingestion

The cell (phagocyte) starts expanding as it surrounds the molecule. This process also involves formation of a vacuole or vesicle around the molecule as it is completely ingested.

(Video) Phagocytosis

Step 4: Digestion

In some cells, enzymes in the vesicle (e.g. lysosome) break down the molecule into simpler components. Waste materials that cannot be used are then removed from the cell through a process known as exocytosis. However, for phagocytes involved in immunity, special structures are known as peroxisomes are created to trap and remove toxic molecules.

Examples of Phagocytosis

  • Phagocytosis of apoptotic cells(efferocytosis)
  • Phagocytosis of bacteria by professional phagocytes
  • Phagocytosis in protozoa

Efferocytosis refers to the process through which apoptotic cells (dead cells) are removed by phagocytic cells. This is one of the most important processes in multicellular organisms given that it contributes to tissue homeostasis in addition to resolving inflammation in the infected site.

* Both professional and non-professional cells can ingest dead cells.

See more on apoptosis

Steps of Efferocytosis (phagocytosis of apoptotic cells)

Step 1: Activation

Efferocytes are activated by a number of molecules released by dead/dying cells. Molecules released by these cells include chemotactic molecules that release the "find- me" signals (triphosphate nucleotides) as well as those that display the "eat-me" signal (phosphatidylserine). Some of the other molecules that have been shown to activate phagocytes include various carbohydrates and proteins.

* Here, then, phagocytes (e.g. macrophages, dendritic cells and endothelial cells etc) use chemotaxis to reach the cells

Step 2: Binding and recognition

Using specialized receptors on their surface, phagocytes interact with the signaling molecules on the surface on the cells which allows them to recognize the cells. This is also achieved through bridging molecules.

* For healthy cells, a molecule referred to as transmembrane protein CD47 has been shown to play an important role in preventing the cell from phagocytosis. When cells die, they lose the molecule.

Step 3: Engulfment

Following the attachment between the phagocyte and the cell, the phagocyte membrane undergoes modification (cytoskeletal rearrangement) which makes it possible to surround the cell from all sides and engulf it.

(Video) Phagocytosis (FL-Immuno/10)

Step 4: Degradation of the cell

During this phase, lysosomal enzymes are released and rapidly degrade the cell. This may take between 60 and 60 minutes.

* Compared to pro-inflammatory responses in higher animals, efferocytosis is described as an immunologically silent process. This is because it is anti-inflammatory. As such, it is involved in the production of anti-inflammatory cytokines and inhibits inflammatory signaling of the cells that are ingested.

Phagocytosis of Bacteria by Professional Phagocytes

Unlike phagocytosis of apoptotic cells where both professional and non-professional phagocytes may be involved, infection by various invading/ pathogenic microorganisms such as bacteria and viruses triggers immune responses where only professional phagocytes are involved.

The following are steps through which phagocytic cells (e.g. monocytes or neutrophils) ingest bacteria:

Step 1: Activation

Infection of a given site in the body stimulates the delivery of neutrophils to the site through chemotaxis. Here, such attractants as tissue debris and bacteria product activate the movement of the phagocytic cells to move to the infected site.

* Neutrophils are able to reach the site fast because they are always circulating in the blood. Through such processes, these cells are able to migrate through the vascular walls to reach the target site.

Step 2:Adherence/Binding

Bacteria with such molecules/ substances as IgG or C3b are easily identified by the phagocytes. Here, such receptors as opsonin receptors on the plasma membrane of the phagocyte bind to these molecules allowing for the bacteria to be identified and ultimately ingested.

Here, it is worth noting that different types of phagocytes have different surface receptors. Therefore, it's only through successful binding with the appropriate surface molecules on the invader that the organism can be ingested.

Step 3: Ingestion/Engulfment

Attachment/binding allows for identification and ingestion of the bacteria. During ingestion, the cell membrane of the phagocyte invaginates while surrounding the bacteria and engulfs it. This process results in the bacteria being enclosed in a vesicle/phagosome within the phagocyte

Step 4: Enzyme action

(Video) The Process Of Phagocytosis

Within the phagocyte (cell) the vesicle containing the invading bacteria comes in contact with the lysosomal granules to form a phagolysosome (digestive vacuole). Here, lysosomal activity helps destroy and kill the bacteria

Phagocytosis Process in Protozoa

Diagram of amoeba engulfing a particle of food by phagocytosis by Kate Taylor [CC0] wikipedia commons

Protozoa are unicellular organisms that can be found in different environments/ habitats. Compared to the other cells described here, protozoa depend on phagocytosis for energy given that the process is used as a feeding mechanism.

* A majority of protozoa are grazers that also feed on single-celled organisms like bacteria and smaller protozoa.

* Some protozoa have a mouth-like opening for feeding while others simply absorb food through their membrane

Based on various studies, phagocytosis in such protozoa species as Amoebaproteus involves steps similar to those of metazoan phagocytes. As such, it involves recognition of the prey,movementtowards the target prey and ingestion of the prey. Therefore, as is the case with such phagocytes as neutrophils, chemotaxis is involved in the phagocytosis process in protozoa.

Phagocytosis in protozoa has in particularly been well demonstrated in the presence of such prey as Tetrahymena. When the ciliates of the prey come in contact with the protozoa, they stimulate the formation of one or more pseudopodia where the prey are trapped (engulfed) and finally ingested.

In culture, protozoa has also been shown to move from an area of low prey (e.g. bacteria) concentration to an area of high prey concentration which shows that they are capable of identifying the prey (through chemotaxis) and moving towards it. Once captured and ingested, the prey remains in the food vacuole where it is acted upon by the appropriate enzymes.

Return to Pinocytosis

Learn more about viruses

Return to Unicellular Organisms and Multicellular Organisms

Return from learning about Phagocytosis to MicroscopeMaster Home

(Video) Phagocytosis: Definition, Steps, Role of ROS, Defects (HD)

Find out how to advertise on MicroscopeMaster!


What is the step by step process of phagocytosis? ›

Phagocytosis can be divided into four main steps: (i) recognition of the target particle, (ii) signaling to activate the internalization machinery, (iii) phagosome formation, and (iv) phagolysosome maturation.

What is phagocytosis with example? ›

phagocytosis, process by which certain living cells called phagocytes ingest or engulf other cells or particles. The phagocyte may be a free-living one-celled organism, such as an amoeba, or one of the body cells, such as a white blood cell.

What are the 7 steps of phagocytosis? ›

Stages of Phagocytosis
  • Activation. Resting phagocytes become activated by inflammatory mediators (e.g. bacterial proteins, capsules, peptidoglycan, prostaglandins, complement proteins). ...
  • Chemotaxis. ...
  • Margination, Rolling and Adhesion. ...
  • Diapedesis. ...
  • Recognition-Attachment. ...
  • Phagocytosis.

What is an example of phagocytosis in biology? ›

Phagocytosis is a cell taking in a large object that it will eventually digest. The classic example is an amoeba eating a bacterium. First, the cell senses the bacterium because of chemicals in the environment. The cell then moves towards the prey.

What are the 5 stages of phagocytosis? ›

The process of phagocytosis involves several steps: (1) particle recognition, (2) particle ingestion, (3) early phagosome formation, (4) late phagosome formation, and (5) phagolysosome formation.

What is an example of phagocytosis in the human body? ›

For example, foreign material in the lymph system is phagocytosed by fixed cells in the lymph nodes; similarly, the vascular system is cleansed by fixed cells in the spleen, liver, and bone marrow that engulf aged red blood cells and foreign bodies. Special cells in the lungs ingest dust particles.

Which of the following are examples of phagocytes? ›

The main types of phagocytes are monocytes, macrophages, neutrophils, tissue dendritic cells, and mast cells.

What are some examples of Pinocytosis? ›

Examples of Pinocytosis

Microvilli in the gut use this process to absorb nutrients from food. Cells in the kidney can use pinocytosis to separate nutrients and fluids from the urine that will be expelled from the body. In addition, human egg cells also use it to absorb nutrients prior to being fertilized.

What are examples of phagocytosis and Pinocytosis? ›

Examples. Phagocytosis: Engulfment of bacteria by white blood cells and engulfment of food particles by cells are examples for phagocytosis. Pinocytosis: Uptaking of enzymes and hormones from the extracellular fluid is an example for pinocytosis.

What is an example of phagocytosis quizlet? ›

"Phagocytosis is the process of certain living cells, called phagocytes, ingesting or engulfing other cells or various particles" (Singh) The phagocytes can either be one-celled organisms, such as an amoeba. Phagocytes can also be body cells, for example a leukocyte or more commonly known as a white blood cell.

What are the steps of phagocytosis quizlet? ›

  • step 1 Chemotaxis. phagocyte is attracted or called towards infection.
  • step 2 Adherence. phagocyte attaches to microbe.
  • step 3 Ingestion. microbe is engulfed in "phagosome"
  • step 4 Phagolysosome formation. lysosome adds digestive chemicals.
  • step 5 Killing. ...
  • step 6 Elimination.

How does phagocytosis work quizlet? ›

Phagocytosis - the process by which particulate matter is engulfed and degraded by a cell. This is in contrast to endocytosis - a process by which soluble macromolecules are taken into a cell. a process by which soluble macromolecules are taken into a cell.

Why is phagocytosis an example of active transport? ›

yes because in both cases vesicles are formed to the inside of the cell and this vesicle formation is an energy consuming process.

What are the 3 types of phagocytes? ›

They are a key component of the innate immune system. There are three main groups of phagocytes: monocytes and macrophages, granulocytes, and dendritic cells, all of which have a slightly different function in the body.

What is phagocytosis performed by? ›

In metazoans, phagocytosis is primarily carried out by specialized cells called professional phagocytes, which include cells of the immune system such as macrophages, neutrophils and dendritic cells [1].

What is an example of endocytosis? ›

And the examples of endocytosis are the leukocytes, neutrophils and monocytes which engulf the foreign particles such as bacteria, etc. And the Metabolism of Cholestrol is a best example for receptor mediated endocytosis.

What is phagocytosis vs pinocytosis? ›

Pinocytosis primarily refers to the uptake of extracellular fluids and small molecules by a cell, whereas phagocytosis is a process by which the cell membrane invaginates around large macromolecular structures (e.g., proteins and viruses) that are otherwise unable to diffuse into the cell.

What is the difference between pinocytosis and phagocytosis? ›

While phagocytosis involves the ingestion of solid material, pinocytosis is the ingestion of surrounding fluid(s). This type of endocytosis allows a cell to engulf dissolved substances that bind to the cell membrane prior to internalization.

Is amoeba an example of phagocytosis? ›

The Phagocytosis process occurs when the cell tries to destroy foreign particles or pathogens such as bacteria or an infected cell by engulfing them and lyse them with lytic enzymes. This process is also observed in single-celled organisms such as amoeba during the ingestion of food particles.

Is phagocytosis an example of diffusion? ›

Phagocytosis is a type of endocytosis, which is when cells ingest molecules via active transport as opposed to molecules passively diffusing through a cell membrane.

What is the process of pinocytosis? ›

Pinocytosis (“pino” means “to drink”) is a process by which the cell takes in the fluids along with dissolved small molecules. In this process, the cell membrane folds and creates small pockets and captures the cellular fluid and dissolved substances.

What is phagocytosis the process of a cell quizlet? ›

"Phagocytosis is the process of certain living cells, called phagocytes, ingesting or engulfing other cells or various particles" (Singh) The phagocytes can either be one-celled organisms, such as an amoeba. Phagocytes can also be body cells, for example a leukocyte or more commonly known as a white blood cell.

What are the steps of Pinocytosis? ›

Pinocytosis occurs in a series of steps, including attraction of positively charged molecules to a negatively charged cell membrane, molecular binding, cell membrane shape-change, invagination, and eventual degradation of vesicular contents by a lysosome.

Which best describes phagocytosis? ›

The correct answer that describes phagocytosis is C. endocytosis of large undissolved particles, such as bacteria or large proteins. When molecules such as bacteria are phagocytized by cells, they will be packaged into membrane-bound vesicles.

What are phagocytes simple definition? ›

(FA-goh-site) A type of immune cell that can surround and kill microorganisms, ingest foreign material, and remove dead cells. It can also boost immune responses. Monocytes, macrophages, and neutrophils are phagocytes.

What is the main killing process in phagocytosis? ›

If the the infection site contains very large numbers of microorganisms and high levels of inflammatory cytokines and chemokines are being produced in response to PAMPs, the phagocyte will empty the contents of its lysosomes by a process called degranulation in order to kill the microorganisms or cell extracellularly.


1. Phagocytosis
(Maureen Richards Immunology & Microbiology)
2. OALD science4
3. Phagocytosis 10th August 2020
(Nafisa Harianawala)
4. Steps in phagocytosis
(Dr. Renuka Joshi)
5. Phagocytosis
(Adimu Show)
6. Phagocytosis
(Wendy Gideon)
Top Articles
Latest Posts
Article information

Author: Mrs. Angelic Larkin

Last Updated: 19/04/2023

Views: 6051

Rating: 4.7 / 5 (47 voted)

Reviews: 86% of readers found this page helpful

Author information

Name: Mrs. Angelic Larkin

Birthday: 1992-06-28

Address: Apt. 413 8275 Mueller Overpass, South Magnolia, IA 99527-6023

Phone: +6824704719725

Job: District Real-Estate Facilitator

Hobby: Letterboxing, Vacation, Poi, Homebrewing, Mountain biking, Slacklining, Cabaret

Introduction: My name is Mrs. Angelic Larkin, I am a cute, charming, funny, determined, inexpensive, joyous, cheerful person who loves writing and wants to share my knowledge and understanding with you.