What are cilia, flagella and pseudopodia

am Puls Biologie 7 RG, textbook

74 4.2 Movement in unicellular organisms Many prokaryotes - bacteria and archaea - are immobile or float freely in the water or in their surroundings. But there are also forms that can actively move. These prokaryotes swim with the help of flagella 1. These are twisted protein threads that are anchored in the cell membrane with a double protein ring (k Fig. 3). The locomotion of the prokaryotes is remarkable in that their flagella do not beat, but rotate - like a ship's propeller. This form of movement is unique among all living beings: no free rotation was observed in any other organisms. Bacteria, so to speak, invented the wheel - long before humans. In the prokaryotes, however, an even stranger movement has been demonstrated: Scientists have shown that bacteria of the genus Pseudomonas walk “upright”. They stand on their narrow end and can thus move forward faster than crawling flat (see Exercise 1). Fig.3: Flagella. The flagella of the prokaryotes are anchored in the membrane with a protein ring, on which they rotate while consuming energy. Some prokaryotes swim with rotating flagella Eukaryotic protozoa crawl, row and swim You are familiar with the amoebas mentioned in Section 4.1 - eukaryotic protozoa up to 0.8mm in size that can move by changing their shape (k Fig. 4). Amoebas “crawl” so to speak. They form plasma processes which are referred to as pseudopodia 2. To do this, the cytoskeleton is contracted on part of the cell - there the pressure in the cytoplasm increases. As a result, the cytoplasm flows to another location in the cell, which then protrudes. The amoeba then forms points of attachment to the subsurface and then follows the rest of the body. Food is also consumed by enclosing the prey with pseudopodia. Paramecium, which belongs to the ciliate species, is also well known (k Fig. 4). This tribe of eukaryotic unicellular organisms is characterized by the fact that its representatives have many short flagella in the membrane that are known as cilia. With a synchronized blink of an eye, the little animals “row” through the water like galleys. But there are also ciliated ciliate animals that use their cilia to create a stream of water to whirl up food. Finally, there are flagellates that carry one or more long flagella, with the help of which they swim through the water (k Fig. 4). Unlike the flagella of the prokaryotes, the flagella do not rotate, but beat like the arms of a swimmer. Some flagellates (especially autotrophic species) can melt the flagella into their bodies even if they are temporarily dry, in order to form them again later. Fig.4: Eukaryotic unicellular organisms show different movement mechanisms. Eukaryotic protozoa move by amoeboid movement, by the stroke of short eyelashes or long flagella Prokaryotes invented the wheel Glossary 1 Flagellum: Latin word for flagellum. Since both prokaryotes and eukaryotes have flagellate-like structures that are completely different (see text), the term “flagellum” is mostly used for prokaryotes, the term “flagellum” for eukaryotes. 2 Pseudopodium: from the Greek pseudo for apparently and podos for foot, in German also referred to as "pseudo-foot". For testing purposes only - property of the publisher öbv

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