Pseudopod
Encyclopedia
Pseudopods or pseudopodia (singular: pseudopodium) (from the Greek
word ψευδοπόδια, ψευδός "fake, false" + πόδια "feet") are temporary projections of eukaryotic cells
. Cells that possess this faculty are generally referred to as amoeboid
s. Pseudopodia extend and contract by the reversible assembly of actin
subunits into microfilament
s. Filaments near the cell's end interact with myosin
which causes contraction. The pseudopodium extends itself until the actin reassembles itself into a network. This is how amoebas move
, as well as some cells found in animals, such as white blood cells.
, and, at its leading edge, the cell forms filaments that subsequently will blend into one another to form networks. It is supposed that actin polymerization is at the origin of the force propelling the cell forwards.
Pseudopodia (which translates to "false feet") are temporary cytoplasm-filled projections of the cell wall that certain eukaryotic cells use for motion or for ingesting nutrients. Most cells with this capability are referred to as amoeboids. Generally several pseudopodia arise from the surface of the body (polypodial-Amoeba proteus) or a single pseudopodium may form on the surface of the body (monopodial-E.histolytica).
Pseudopodia are formed by microtubule
and filament structures. The cell surface projects a membrane process called the lamellipodium, which is supported inside by filaments that form at the leading edge, turning into networks as they blend together. Cytoplasm flows into the lamelliopdium, forming the pseudopodia.
The functions of pseudopodia include locomotion and the capturing of prey. Pseudopodia are critical in sensing prey that can then be engulfed; the engulfing pseudopodia are called phagocytosis pseudopodia. A common example of this sort of amoeboid cell is the human white blood cell.
Pseudopodia don't all look like amorphous blobs; instead, they can be classified by their distinct appearances. Lobopodia are bulbous and amoebic. Filopodia are slender, sort of football shaped, and are supported largely by microfilaments. Reticulopodia are very complex and bear individual pseudopodia that form irregular nets. Axopodia are the phagocytosis type with long, thin pseudopods supported by complex, microtubule arrays enveloped with cytoplasm, and they respond rapidly to physical contact.
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word ψευδοπόδια, ψευδός "fake, false" + πόδια "feet") are temporary projections of eukaryotic cells
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
. Cells that possess this faculty are generally referred to as amoeboid
Amoeboid
Amoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
s. Pseudopodia extend and contract by the reversible assembly of actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
subunits into microfilament
Microfilament
Microfilaments are the thinnest filaments of the cytoskeleton, a structure found in the cytoplasm of all eukaryotic cells. These linear polymers of actin subunits are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton...
s. Filaments near the cell's end interact with myosin
Myosin
Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
which causes contraction. The pseudopodium extends itself until the actin reassembles itself into a network. This is how amoebas move
Amoeboid movement
Amoeboid movement is a crawling-like type of movement accomplished by protrusion of cytoplasm of the cell involving the formation of pseudopodia. The cytoplasm slides and forms a pseudopodium in front to move the cell forward. This type of movement has been linked to changes in action potential;...
, as well as some cells found in animals, such as white blood cells.
Reproduction
First, the cell surface extends a membrane process, a lamellipodium. Actin polymerizesPolymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
, and, at its leading edge, the cell forms filaments that subsequently will blend into one another to form networks. It is supposed that actin polymerization is at the origin of the force propelling the cell forwards.
Pseudopodia (which translates to "false feet") are temporary cytoplasm-filled projections of the cell wall that certain eukaryotic cells use for motion or for ingesting nutrients. Most cells with this capability are referred to as amoeboids. Generally several pseudopodia arise from the surface of the body (polypodial-Amoeba proteus) or a single pseudopodium may form on the surface of the body (monopodial-E.histolytica).
Pseudopodia are formed by microtubule
Microtubule
Microtubules are a component of the cytoskeleton. These rope-like polymers of tubulin can grow as long as 25 micrometers and are highly dynamic. The outer diameter of microtubule is about 25 nm. Microtubules are important for maintaining cell structure, providing platforms for intracellular...
and filament structures. The cell surface projects a membrane process called the lamellipodium, which is supported inside by filaments that form at the leading edge, turning into networks as they blend together. Cytoplasm flows into the lamelliopdium, forming the pseudopodia.
The functions of pseudopodia include locomotion and the capturing of prey. Pseudopodia are critical in sensing prey that can then be engulfed; the engulfing pseudopodia are called phagocytosis pseudopodia. A common example of this sort of amoeboid cell is the human white blood cell.
Pseudopodia don't all look like amorphous blobs; instead, they can be classified by their distinct appearances. Lobopodia are bulbous and amoebic. Filopodia are slender, sort of football shaped, and are supported largely by microfilaments. Reticulopodia are very complex and bear individual pseudopodia that form irregular nets. Axopodia are the phagocytosis type with long, thin pseudopods supported by complex, microtubule arrays enveloped with cytoplasm, and they respond rapidly to physical contact.
Morphology
Pseudopods can be classified into several varieties according to their appearance:- Lobopodia are bulbous, short and blunt in form. They are very typical of AmoebozoaAmoebozoaThe Amoebozoa are a major group of amoeboid protozoa, including the majority that move by means ofinternal cytoplasmic flow. Their pseudopodia are characteristically blunt and finger-like,...
. These finger-like, tubular pseudopodia contain both ectoplasmEctoplasmEctoplasm may refer to:* Ectoplasm , the outer part of the cytoplasm* Ectoplasm , supposed physical substance that manifests as a result of spiritual energy or psychic phenomenon...
and endoplasmEndoplasmEndoplasm generally refers to the inner part of a cell's cytoplasm. This is opposed to the ectoplasm which is the outer layer of the cytoplasm....
. - FilopodiaFilopodiaFilopodia are slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating cells. They contain actin filaments cross-linked into bundles by actin-binding proteins, e.g. fascin and fimbrin. Filopodia form focal adhesions with the substratum, linking it to the...
are more slender and filiform with pointed ends, consisting mainly of ectoplasmEctoplasm (cell biology)Ectoplasm refers to the outer, non-granulated part of a cell's cytoplasm. This is opposed to the endoplasm which is the inner layer of the cytoplasm, and often is granulated. It is clear, and protects as well as transports things within the cell. Moreover, large numbers of actin filaments...
. These formations are supported by microfilamentMicrofilamentMicrofilaments are the thinnest filaments of the cytoskeleton, a structure found in the cytoplasm of all eukaryotic cells. These linear polymers of actin subunits are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton...
s. This is observed in EuglyphaEuglyphaEuglypha is a genus of Rhizaria. It includes the species Euglypha rotunda....
and Lecithium. - Reticulopodia, also known as reticulose pseudopods, are complex formations where individual pseudopods are blended together and form irregular nets. The primary function of reticulopodia, also known as myxopodia, is the ingestion of food, and the secondary function is locomotion. Reticulopods are typical of ForaminiferaForaminiferaThe Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
. - Axopodia (also known as actinopodia) are thin pseudopods containing complex arrays of microtubuleMicrotubuleMicrotubules are a component of the cytoskeleton. These rope-like polymers of tubulin can grow as long as 25 micrometers and are highly dynamic. The outer diameter of microtubule is about 25 nm. Microtubules are important for maintaining cell structure, providing platforms for intracellular...
s and are enveloped by cytoplasmCytoplasmThe cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
. Axopodia are mostly responsible for phagocytosis by rapidly retracting in response to physical contacts. They are observed in radiolaria and heliozoaHeliozoaHeliozoa are phagotrophs. They are roughly spherical amoeboids with many stiff, microtubule-supported projections called axopods radiating outward from the cell surface. These give them the characteristic sun-like appearance for which they are named, and are variously used for capturing food,...
. This supposedly [citation or further research needed] takes a strain on the helix, for after the sensory action has occurred, it then later on dies. Principally, these pseudopodia are food collecting structures.