- Also called:
- pseudopod movement
- Related Topics:
- Protozoan
- slime mold
- amoeba
- pseudopodium
- amoeboid locomotion
Pseudopodial locomotion
-
What is pseudopodial locomotion?
Pseudopodial locomotion is a type of movement used by eukaryotic cells, especially amoebas and slime molds. It involves the extension of a temporary membrane projection called a pseudopodium, which fills with cytoplasm.
The process includes extension, attachment, contraction, cytoplasmic flow, gel-sol transformation, and detachment and pseudopod retraction. Cells anchor to a substrate, rearrange cytoskeletal components, and contract to move in the direction of the pseudopodium. Actin filaments facilitate the liquid-to-gel transformation required for gliding on a surface. Though adaptable, this movement is slow compared to other forms, such as cilia or flagella.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Which types of organisms move using pseudopodial locomotion?
Pseudopodial locomotion is a type of movement used by cells that involves extending a temporary projection of the cell membrane, called a pseudopodium, and then flowing the cell's contents into the extension.
Organisms that use pseudopodial locomotion include:
* Certain eukaryotes, such as slime molds and protozoans like amoebas.
* Some cells in multicellular organisms, such as white blood cells and some tumor cells.
* Foraminiferans, which move by extending slender pseudopodia called filapodia.
* Heliozoans, which extend and shorten axopodia for movement.
* Radiolarians use thin, stiff pseudopodia to help them float.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What is a pseudopod, and how is it formed?
A pseudopodium is a temporary or semipermanent extension of a cell's cytoplasm that certain eukaryotes use for locomotion, capturing materials, and feeding.
Pseudopodial locomotion occurs through these steps:
* The cell extends a pseudopodium, a projection of membrane and cytoplasm, outward.
* The cell anchors to a substrate, and cytoskeletal components rearrange and shorten to pull the cell in the direction of the membrane projection. Cytoplasm flows into the pseudopodium.
* The rear of the cell detaches from the substrate and contracts, moving the cell. The pseudopodium then retracts.The assembly and disassembly of actin filaments drive this movement.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do organisms use pseudopods to move?
Organisms use pseudopodia, temporary extensions of cytoplasm, for movement and feeding. This type of movement, known as pseudopodial locomotion, involves several steps: extension, attachment, contraction, cytoplasmic flow, gel-sol transformation, detachment, and pseudopod retraction.
During extension, the cell creates a temporary projection of membrane and cytoplasm, called a pseudopodium, that extends outward. The cell then anchors itself to a substrate, which allows the cell to contract and pull itself in the direction of the membrane projection. As the cell contracts, cytoplasm flows into the pseudopodium.
Different organisms form distinct types of pseudopodia, including lobopodia, filopodia, reticulopodia, and axopodia.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What role does the cytoplasm play in pseudopodial movement?
In pseudopodial movement, the cytoplasm plays a central role. Amoebas, for example, have cytoplasm divided into ectoplasm (a peripheral gel layer) and endoplasm (an inner fluid mass).
During movement, the ectoplasm converts to a fluid sol, prompting the endoplasm to flow towards this area, which extends the pseudopodium. As the endoplasm reaches the tip, it turns into a gel, thus extending the pseudopodium. The cell then empties its body into the extended pseudopodium, effectively turning it into the main body. This flow is facilitated by proteins, similar to those in muscle contraction.
7 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does pseudopodial locomotion help organisms survive in their environments?
Pseudopodial locomotion is a type of movement used by eukaryotes, such as amoebas and slime molds, as well as some cells in multicellular organisms, like white blood cells. It involves extending a temporary membrane projection, called a pseudopodium, and flowing cellular contents into it.
This type of movement is highly adaptable, allowing cells to navigate various surfaces and mediums like water. For example, foraminiferans use stiff pseudopodia to swim, while radiolarians use thin, stiff pseudopodia to float. The process involves several steps, including extension, attachment, contraction, cytoplasmic flow, gel-sol transformation, detachment, and pseudopod retraction. Pseudopodial locomotion also helps organisms like amoebas feed by engulfing prey.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Pseudopodial locomotion, movement that results when a cell extends a temporary projection of membrane and then flows its cellular contents to fill the extension. Pseudopodial locomotion is a type of cellular movement used by certain eukaryotes, particularly slime molds and certain types of protozoans, such as amoebas. In multicellular organisms, some motile cell types, such as white blood cells and some kinds of tumour cells, also use a form of pseudopodial locomotion. In addition, some organisms utilize a modified form of pseudopodial locomotion to capture materials; phagocytosis pseudopodia, for example, help sense and engulf materials.
Process
Pseudopodial locomotion consists of several steps, including extension, attachment, contraction and cytoplasmic flow, gel-sol transformation, and detachment and pseudopod retraction. In extension, the cell generates a temporary projection of membrane and cytoplasm—called a pseudopodium—which extends outward in a specific direction; this process is controlled via the assembly and disassembly of cytoskeletal components, especially actin filaments. In attachment, the cell anchors itself to the substrate, facilitating the contraction phase of movement, in which cytoskeletal components rearrange and shorten themselves to pull the cell in the direction of the temporary membrane projection. Contraction of the cell causes cytoplasm to flow into the pseudopodium.
Most pseudopodial locomotion requires a substrate on which the cell can glide. This process is facilitated by gel-sol transformation, in which the cytoplasm of the moving cell changes from a liquid state to a more gel-like state. Gel-sol transformation is aided by a flexible network of actin filaments; as pseudopodial locomotion progresses, the assembly and disassembly of microfilament structures made of actin and myosin drive the cell’s movement. In detachment, the rear portion of the cell releases from the substrate and contracts, allowing the entire cell to move in the desired direction; the pseudopodium then retracts.
" height="20" alt="HEW Logo">
Among protists, pseudopodial locomotion is considered slow relative to other forms of locomotion, such as movement via cilia or flagella. Estimates of average velocity for pseudopodial locomotion range from 5 μm/sec to 20 μm/min. Phagocytes in the human body may move a few millimetres per day using this motion.
Mechanisms
Pseudopodial locomotion is a highly flexible and adaptable kind of movement, making it possible for cells to navigate across a variety of surfaces and through different mediums, such as water. Thus, the mechanisms by which pseudopodia drive movement can vary markedly. Foraminiferans, for example, use stiff pseudopodia that poke through holes in a shell to swim, while radiolarians use thin stiff pseudopodia to help them float through water. Members of the ocean protist genera Sticholonche move using axopodia, semipermanent pseudopodia that rotate like oars anchored in sockets. Heliozoans alternately extend and shorten their axopodia for movement.
Structures
Different types of organisms and cells form distinct types of pseudopodia, which are distinguished by their shape and structure. These include: lobopodia, filopodia, reticulopodia, and axopodia. Lobopodia are fingerlike, with rounded ends, and may be flattened or tubular. They are generally produced one or two at a time per cell. These lumpy pseudopodia can be used to creep across surfaces, such as the bottom of a pond. Filopodia are more slender with pointed ends that can branch. Multiple filopodia can be produced at one time. Reticulopodia are branching filaments that form in foraminiferans; these structures can connect with one another to make dense networks. Axopodia are long and sticky pseudopodia with an internal rod made of microtubules; these are especially prominent in radiolarians and heliozoans.
The projections that drive movement in motile cells within multicellular organisms often have the same structure as amoeboid pseudopodia. However, in some instances, they are thinner. Such thin structures are known as lamellipodia; lamellipodia depend heavily on adhesion to a surface to propel cell movement. The term lamellipodia is sometimes also used to describe broad, flat pseudopodia in amoeba.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
