Pseudopods – Definition, Function, Movement, And Examples

Pseudopods are tiny structures found in some plants, often referred to as “false feet”, which are often overlooked in the study of microbiology.

Pseudopods - Definition, Function, Movement, And Examples

Want to learn more about these curious organisms, including what they do and why they are there? Then read on for all you need to know!

What Is A Cell Membrane?

Before we move to look at pseudopodia in more detail, it is useful to have a brief overview of the cell membrane, as this is a term that we will be using throughout the discussion.

A cell membrane is simply the outermost layer of the cell, and is made up of two layers; the inner plasma membrane and the outer glycocalyx.

The plasma membrane is made up of phospholipid molecules (which are fat-soluble) and proteins, while the glycocalyx consists of carbohydrate molecules.

These two layers are connected by pores called tight junctions, which allow nutrients and waste products to pass through the membrane.

Both layers contain receptors that detect changes in the environment around them and trigger appropriate responses.

For example, when the cell senses a change in temperature, its response is to alter the permeability of the membrane so that heat can enter the cell.

This allows the cell to respond appropriately to the new conditions.

When a cell wants to move, it extends pseudopods outwards from the cell membrane and uses them to push itself forward.

These pseudopods are formed when the actin cytoskeleton is activated, and this is done by a protein called Rho GTPase.

Once the pseudopods have been extended, the cell then begins to contract them back again, pulling on the cell membrane until it has moved forwards.

How Do Cells Move?

Cells move using three basic methods: crawling, gliding, and swimming. All of these movements involve the extension and retraction of pseudopods. 

How Does A Cell Extend Its Pseudopods?

A cell extends its pseudopods by sending out protrusions known as filaments. These filaments extend outwards from the cell body and eventually reach the edge of the cell.

At this point, they connect to neighboring cells, allowing the cell to spread out. If the cell does not want to spread out, it retracts the filament back into the cell body.

How Does A Cell Retract Its Pseudopods

A cell retracts its pseudopods by pulling them back into the cell body, where they become part of the cytoskeleton.

The actin and myosin molecules in the cytoskeleton contract, causing the pseudopods to shrink back into the cell.

What Is An Eukaryotic Organism?

Eukaryotic organisms are those which contain organelles within their cells and are therefore classified as eukaryotes.

These include plants, algae, fungi, protists, slime molds, and animals.

The term “eukaryote” comes from the Greek word ευκαρίων (eukykárion), meaning ‘goodly’, referring to the fact that these organisms were considered to be more advanced than prokaryotes.

However, there are many differences between the two types of organisms, and these will be discussed later on.

Eukaryotic organisms are generally divided into three main categories: unikonts, bikonts, and trichonts. Unikonts consist of animals, algae, fungi, and slime molds.

Bikonts consist of protists, such as ciliates and dinoflagellates, and trichont consists of Plantae, such as mosses, ferns, and gymnosperms.

What Is Cell Theory?

Cell theory was first proposed by Matthias Schleiden and Theodor Schwann in 1838, who described the basic unit of life as an individual cell.

In 1839 Julius von Sachs suggested that the nucleus was the center of each cell, and in 1843 Rudolf Virchow proposed that the nucleus was surrounded by a membrane.

In 1855 August Weismann proposed that the cell was not homogeneous and that the nucleus contained the hereditary information.

The discovery of DNA in 1953 led to further research into the nature of heredity, and in 1958 James Watson and Francis Crick discovered the structure of DNA.

This led to the development of molecular biology and the study of genes and proteins.

What Are The Types Of Cells?

Before we take a closer look at pseudopods, it is worth taking a little time to understand the types of cells; this offers context and helps us to understand where pseudopods fit into the bigger picture.

There are many different types of cells; each type has a specific function within the organism. There are three main categories: prokaryotic, eukaryotic, and unicellular.

Prokaryotes are bacteria, archaea, and other microbes. Eukaryotes include plants, animals, fungi, protists, and algae.

Unicellular organisms are those without a nucleus, such as slime molds.

Prokaryotes

Prokaryotes are the simplest form of life, consisting of only one cell. These cells lack a nucleus and are not capable of performing any metabolic processes.

They are generally found in extreme environments, such as hot springs, deep-sea vents, and volcanic areas.

They are often very simple in appearance and consist of little more than a membrane enclosing a fluid-filled compartment.

Some species are able to perform photosynthesis, while others use chemosynthetic reactions.

Eukaryotes

Eukaryotes are the most complex form of life. They contain a nucleus, which contains genetic information. They are further divided into two groups: multicellular and unicellular.

Multicellular organisms are made up of individual cells joined together to form tissues and organs. In contrast, unicellular organisms are made from just one cell.

Eukaryotes are found everywhere on Earth but are especially abundant in warm, moist places.

Most eukaryotes are plant or animal-based, although there are some notable exceptions.

Unicellular Organisms

Unicellular organisms can be classified into several major groups: Protista (single-celled), Fungi, Algae, Protozoa, and Animalia.

  • Protist

Protists are single-celled organisms. They are often described as being “simple” because their structure consists of a single cell containing no organelles.

However, it’s important to note that even though all protists are single cells, they do not necessarily look like single cells.

A good example of this would be the Euglenophyta, a group of green algae which have a number of flagella at the end of their bodies.

  • Fungi

Fungi are eukaryotic organisms that reproduce by spores. Spores are produced in special structures called conidiophores.

Conidiophores produce small, spore-forming fruiting bodies called conidia. The majority of fungi are saprophytes, meaning that they feed off decaying organic matter.

Many fungi are parasites and cause disease in humans and animals.

The best-known examples of fungal diseases are candidiasis, cryptococcosis, histoplasmosis, coccidioidomycosis, and blastomycosis.

  • Algae

Algae are a diverse group of aquatic plants that live in fresh and saltwater. They are usually motile and can move using cilia, flagella, or both.

Most algae are photosynthetic and obtain energy through light-dependent reactions.

Some algae also perform dark respiration, where oxygen is reduced during the process of carbon dioxide fixation. Algae are used for food, fuel, medicine, and industry.

  • Protozoa

Protozoans are single-cellular organisms that lack nuclei.

There are many different types of protozoa, including amoebae, paramecia, trichomonads, trypanosomes, kinetoplastids, and ciliates.

Amoebae are free-living, feeding on bacteria and other microorganisms. Paramecium are microscopic swimming creatures with an outer shell.

Trichomonas vaginalis is a parasite that lives in the human urogenital tract. Trypanosomes are parasitic protozoans that infect insects and mammals.

Kinetoplastids include Leishmania, which causes leishmaniasis; Plasmodium, which causes malaria; and Toxoplasma gondii, which causes toxoplasmosis.

Ciliates are a large group of single-celled protozoan organisms that includes species such as Tetrahymena and Paramecium.

  • Animalia

Animals are multicellular organisms composed of various body parts. Animals have a common ancestor with plants, algae, and fungi.

All animals derive from eukaryotic cells and thus share many similar characteristics. For instance, they all use DNA to pass down traits from generation to generation.

Animals also have specialized organs called excretory systems, digestive systems, circulatory systems, nervous systems, reproductive systems, and locomotive systems.

Parts Of A Cell

The main components of a cell include:

  • Cell Membrane

The cell membrane is the outer layer of a cell and is composed of phospholipids and proteins.

It acts as a barrier, preventing harmful chemicals from entering the cell while allowing beneficial ones to pass through.

It also forms a boundary between the inside and outside of the cell.

  • Nucleus

The nucleus is where DNA is stored and is surrounded by a nuclear envelope, which contains the nuclear pore complexes (NPCs).

These allow nucleotides and proteins to enter and leave the nucleus.

  • Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a system of membranes that surrounds the nucleus. It is involved in protein synthesis and is where ribosomes are found.

  • Mitochondria

Mitochondria are organelles that produce energy for the cell. They contain their own DNA and are surrounded by a double membrane.

  • Golgi Apparatus

The Golgi apparatus is a series of stacks of vesicles that work to sort out proteins and lipids and package them into smaller units. It is located at the center of the cell.

  • Microtubules

Microtubules are long structures made up of tubulin, which are used to transport materials around the cell. They can be either parallel or antiparallel.

What Is Cytoplasm?

The cytoplasm is the fluid within cells and is responsible for carrying nutrients and other necessary substances from one part of the cell to another.

In addition to this, it provides structural support to the cell and helps to maintain the shape of the cell.

It is also important for the transmission of signals between different parts of the cell.

What Are Pseudopods?

What Are Pseudopods?

A pseudopod is a small structure that often resembles an arm, which often projects from the cell membrane of a eukaryotic organism.

They are responsible for facilitating movement and feeling within the membrane and are found as temporary extensions of the cytoplasm of a cell.

In more complex organisms, such as animals, pseudopods are also present in a number of cells where they have the job of detecting, trapping, and destroying any unwanted microbes that try to make their way into the organism.

There are four main types of pseudopods, and these have variations in both appearance and function.

Types Of Pseudopods

The four main types of pseudopods are: 

  • Filopodia

These are thin, finger-like projections that are filled with groups of actin filaments arranged in parallels.

Filopodia are most commonly found in multicellular organisms as opposed to single cellular organisms, and in the former, they extend well into the extracellular matrix, where they play a key role in sending and receiving signals.

In most cases, filopodia are thought to serve exploratory or ascribed sensory functions, and their formation is usually associated with the protrusion of actin filament, arranged in sheets, known as membrane ruffles and lamellipodia.

It is important to note, however, that research in this area is still ongoing.

  • Axopodia

This is a similar structure to filopodia, but instead of being made up of parallel actin filaments, axopodia are made up of bundles of microtubules.

They tend to be much more rigid than Filopodia, making them less susceptible to bending and are needle-like in appearance, with long, thin strands all across the surface.

Axopodia are most commonly used for feeding, and have a sticky substance located on the surface – this is created by mucocysts, and works in conjunction with keratocysts.

When working together, these two features eject long, thin structures onto the surface, which trap food and material to the surface, before these are transported throughout the cell and into the body of the cell using the cytoplasmic stream.

A single axopodia can trap small prey, it may require several to capture larger materials.

In some cases, axopodia have also been shown to aid with the movement of the cell, and this is more common in aquatic or marine environments.

It also allows the cell to have greater control over the direction that they move in, as well as the speed. It should be noted that axopodia are lost during the cell division process.

  •  Reticulipodium

Reticulipodium, or reticulopodia, may also be referred to as rhizopodia or extrathalamous cytoplasm, and are dynamic, thread-like pseudopodia that branch out and fuse together.

They are formed of the cytoplasm and tubules and are present in a wide range of organisms, including foraminiferans and Endomyxa amoebae.

Their primary purpose is for movement and feeding and may reach through pores in a cell.

Their ultimate goal is to form a web-like network, composed of these tiny threads connected together as one.

  • Lobopodia

Lopdodia are amongst the most common of all pseudopia, and have finger-like tubes making up their structure – there are made of endoplasm and ectoplasm.

Lobopodia have also been proven to include myosin and actin, and this helps them to play a key role in allowing the cell to move.

The microtubules here are less well developed than other organisms, and so the role of this type is usually restricted to helping the cell move.

What Is The Function Of Pseudopods?

The function of pseudopods varies from organism to organism, and even within an individual cell. Some examples of how they work include:

  • Exploring the environment

Pseudopods are often used for exploration and are very useful when trying to find new places to live.

In many cases, they are able to sense the location of nutrients, and will then extend themselves towards the source.

This helps cells to locate areas rich in resources, such as oxygen, glucose, minerals, or other chemicals.

  • Sensing the environment

Some cells use pseudopods to sense the environment around them.

For example, if there is a chemical in the air or water, the cell will use its pseudopods to explore the surrounding area.

If the cell detects something harmful, it will retract the pseudopods.

  • Feeding

Many cells use pseudopods for feeding. These are often called phagocytes, as they engulf foreign particles.

They do this by extending their pseudopods and then pulling the particle inside. Once the particle has been engulfed, the cell will digest it.

  • Moving

Many cells use pseudopods when moving. This includes crawling, swimming, gliding, and walking.

Cells need to move in order to grow, divide, migrate, and communicate with each other.

What Is The Connection Between Cytoplasm And Pseudopods?

The cytoplasm is the main component of the cell and is made up of proteins, enzymes, lipids, carbohydrates, nucleotides, and DNA.

It is responsible for all of the functions of the cell and contains everything needed for the cell to survive.

Pseudopods are extensions of the cytoplasm, which allow the cell to move and interact with its surroundings.

They are usually found at the tips of the cell, but may also be found on the sides of the cell, and along the edges of the cell.

They can vary greatly between different types of cells, and even within the same type of cell.

Why Are Pseudopods Important?

There are several reasons why pseudopods are important. First, they help cells to move and feed. Second, they are involved in sensing the environment around the cell.

Third, they play a role in communication between cells. Finally, they are essential for growth and division.

  • Movement

Pseudopod formation allows cells to move and crawl across surfaces. When cells are attached to a surface, they cannot move unless they have pseudopods.

Without them, they would not be able to pull away from the surface.

  • Communication

When two cells come into contact with each other, they must first make sure that they are compatible.

This means that the cells must recognize each other’s identity, and determine whether they should attach or detach.

To do this, they use pseudopods to communicate with one another.

  • Growth and Division

When cells divide, they must separate their contents so that each daughter cell receives half of what was once one cell. This requires the cell to break down and re-form itself.

During this process, the cell needs to take in nutrients and expel waste products. The best way to accomplish these tasks is through the extension of pseudopods.

Final Thoughts

Pseudopods are curious structures, but ones that play a key role in the movement, feeding, and communication of cells.

By learning more about them, you are helping to expand your understanding of the wonders of the natural world.

Jennifer Dawkins