The movement of eukaryotic cells

Abstract

Microtubule- and micro filament-dependent motility in eukaryotic cells is a phenomenon that can be expressed in a number of ways, resulting in either the movement of the cell as a whole or only a part of it. In the first case an active locomotion is generated, in the second the movement is localized to a specific part of the cell, such as the membrane, the cytoplasmic organelles or the cytoplasm itself. Cell locomotion depends on two principal types of movement: the ciliary or flagellar movement and the amoeboid movement. Cilia and flagella of eukaryotic cells are cylindrical organelles, which when animated, propagate waves resulting in the movement of the cells, which are free to move. In fact, when cells are not free to move, ciliary and flagellar beating results in the movement of fluid around them. This is the case in the ciliate epithelia which lines cavities in the body of animals, and many other examples can be found in the biological world. It is evident that motility depending on cilia and flagella can occur only in liquid environments. Amoeboid movement, on the contrary, is effective for the locomotion of cells in non-liquid environments. It is found not only in free-living micro-organisms but also in the higher living forms where it plays a crucial role during development and particularly in the morphogenetic arrangement of multicellular organisms (see Cellular Development by D. R. Garrod in this series).