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Clockwise from top right: Amoeba proteus, Actinophrys sol, Acanthamoeba sp., Nuclearia thermophila., Euglypha acanthophora, neutrophil ingesting bacteria. An amoeba (/ ə ˈ m iː b ə /; less commonly spelled ameba or amœba; pl.: amoebas (less commonly, amebas) or amoebae (amebae) / ə ˈ m iː b i /), [1] often called an amoeboid, is a type of cell or unicellular organism with the ability ...
The ectoplasm consists of a gelatinous semisolid called plasma gel whereas the endoplasm is made up of a less viscous fluid called plasma sol. The ectoplasm owes its highly viscous state, in part, to the cross-linking actomyosin complex. Locomotion of an amoeba is thought to occur due to the sol-gel conversion of the protoplasm within its cell.
In order to initiate fast escape responses, these may have been coupled directly to the motility apparatus—particularly to flexible, membrane-continuous structures such as cilia and pseudopodia. Loss of voltage-gated sodium / calcium channels is further correlated with loss of cilia in many taxa.
The actin polymers then push the membrane as they grow, forming the pseudopod. The pseudopodium can then adhere to a surface via its adhesion proteins (e.g. integrins), and then pull the cell's body forward via contraction of an actin-myosin complex in the pseudopod. [9] [10] This type of locomotion is called amoeboid movement.
The body and oral kinetids make up the infraciliature, an organization unique to the ciliates and important in their classification, and include various fibrils and microtubules involved in coordinating the cilia. In some forms there are also body polykinetids, for instance, among the spirotrichs where they generally form bristles called cirri.
Those that feed on soluble molecules [130]: 218 or macromolecules under 0.5 μm in size are called osmotrophs, [129] and they absorb them by diffusion, ciliary pits, transport proteins of the cell membrane, and a type of endocytosis (i.e., invagination of the cell membrane into vacuoles, called endosomes) known as pinocytosis [2] or fluid-phase ...
Ciliates (which move by using hair-like structures called cilia) and amoebae (which move by the use of temporary extensions of cytoplasm called pseudopodia). Many protozoa, such as the agents of amoebic meningitis, use both pseudopodia and flagella. Some protozoa attach to the substrate or form cysts, so they do not move around . Most sessile ...
An amoeba of the genus Mayorella (Amoebozoa, Discosea) Amoebozoa is a large and diverse group, but certain features are common to many of its members. The amoebozoan cell is typically divided into a granular central mass, called endoplasm, and a clear outer layer, called ectoplasm. During locomotion, the endoplasm flows forwards and the ...