Flagella


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flagella

[flə′jel·ə]
(biology)
Relatively long, whiplike, centriole-based locomotor organelles on some motile cells.

Flagella

 

cytoplasmic processes of a cell, characteristic of all flagellates and many bacteria, zoospores, and spermatozoa of all plants and animals.

Earlier, flagella were considered in contraposition to cilia. Electron-microscope investigations have shown the structural resemblance of these processes, which differ from one another only in number: a cell usually has one or several flagella and many cilia (up to several thousand). For this reason the terms “flagella” and “cilia” are often used as synonyms. The lengths of flagella vary greatly from cell to cell, and their diameters are each approximately 0.2 microns. Each flagellum has a shaft covered with a plasmic membrane (a continuation of the cell membrane) and consisting of a homogeneous substance, of which there are nine double fibrils along the periphery and two single fibrils in the center (thickness 250-600 A) with an electronically denser edge and a less dense central area; for this reason the fibrils are called microtubules. At the base of the flagellum is the basal body, a homologue of the centriole. Several forms of movement are distinguished in flagella: rotary, including spiral, motion; undulating motion, with wavelike movement from the free end to the base of the flagellum; and paddle-stroke motion. A similarity between the protein of flagella and the proteins of muscle has been discovered.

M. E. ASPIZ

References in periodicals archive ?
The antennules of the Baltic shrimp Palaemon adspersus are sensory organs comprising two slender, filiform flagella, lateral and medial, both of which are implanted on a common rigid peduncle.
Arrow heads in (a) and in (b) indicate anterior flagella and undulating membrane, respectively (630x).
For examination and recording of the disintegration of sperm flagella by microtubule sliding, the 40x BM objective was usually used, while the 100x DL objective was for more precise measurement.
Further experiments with knockout mutants showed that SsaI produces quorum-sensing signals that control the formation of flagella and motility.
Four of these flagella are used for movement and the fifth may help direction.
23) have reported that the fraction of flagella induce an important protection we decided to study this fraction and the antigens of membrane of epimastigotes to see if they elicited a better response in mononuclear cells of patients.
In the front gallery, Moffett showed three monochromes, bristly sculptural paintings resembling patches of Astroturf or dense clusters of flagella (each a sliver of oil paint squeezed directly from the tube).
In contrast, the fliA and the flhD mutants that are unable to produce flagella produced a biofilm that was quantitatively similar to wild-type, but less well structured.
According to a study in Physical Review Letters, E coli bacteria and other pathogens swimming with flagella or tails move straight ahead when not faced with obstructions, but near a surface or obstacle the bacteria "swim to the left" often getting stuck in minute crevices in the process, such as those on the surface of catheters.
Once the cells fuse, long, threadlike appendages known as flagella are lost, he said.
In general, flagella and cilia of eukaryotes show an axoneme composed of a 9 + 2 microtubular pattern.
In his role as an ID proponent, he claims that biological structures such as bacterial flagella are "irreducibly complex," meaning that their parts could not have been assembled over time by natural selection and that the absence of one part would by definition make the entire structure nonfunctional.