Protozoan Organelles of Locomotion

Abstract

Structures responsible for locomotion of single‐celled protozoa are referred to as organelles because they comprise only part of a cell that is performing all of the functions of a complete organism. Organelles that produce motion may move the whole organism from place to place, or may change the shape of the cell or the position of components within it.

Keywords: cilia; flagella; pseudopodia; myonemes

Figure 1.

Diagram to illustrate the principles believed to drive the movement of Amoeba. Actin filaments exist in the cortical ectoplasm, and are capable of exerting contractile pressure on the more fluid endoplasm. Contraction of ectoplasm at the tail end (left) causes solation of the cytoplasm and depolymerization of the actin filaments. The pressure created propels endoplasm towards the right through a tube whose walls exert enough tension that endoplasm only escapes at the tip of the extending pseudopod (right end). Here endoplasm spreads and gelates to extend the ectoplasmic tube, as actin filaments repolymerize. (Modified from Sleigh, .)

Figure 2.

Comparison of the propulsion of water (red arrows) by a flagellum (a) with that by a cilium (b) as a result of motion by these organelles indicated by blue arrows (see text). (Modified from Sleigh, .)

Figure 3.

Comparison of (a) the action of dynein molecules (d) in generating sliding motion between two microtubules, A and B, with (b) the action of a myosin filament (m) in drawing together the attachment points of two actin microfilaments (mf) (see further description in the text). (Modified from Sleigh, .)

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References

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Further Reading

Alberts B, Bray D, Lewis J et al. (eds) (1983 and later editions) Molecular Biology of the Cell. New York: Garland.

Allen RD and Kamiya N (eds) (1964) Primitive Motile Systems in Cell Biology. New York: Academic Press.

Inoue S and Stephens RE (1975) Molecules and Cell Movement. New York: Raven Press.

Preston TM, King CA and Hyams JS (1990) The Cytoskeleton and Cell Motility. London: Chapman and Hall.

Satir P and Sleigh MA (1990) The physiology of cilia and mucociliary interactions. Annual Review of Physiology 52: 137–155.

Sleigh MA (ed.) (1974) Cilia and Flagella. London: Academic Press.

Sleigh MA (1984) Motile systems of ciliates. Protistologica 20: 299–305.

Sleigh MA (1989) Protozoa and Other Protists. Cambridge: University Press.

Sleigh MA and Pitelka DR (1974) Processes of contractility in Protozoa. Actualités Protozoologiques 1: 293–306. (Université de Clermont).

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How to Cite close
Sleigh, Michael A(May 2001) Protozoan Organelles of Locomotion. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001931]