Eukaryote cells phagocytosis

The cytoskeletons of other eukaryotic cells typically include both microtubules and microfilaments, which consist of long, chainlike oligomers of the proteins tubulin and actin, respectively. Bundles of microfilaments often lie just underneath the plasma membrane (fig. 17.22). They participate in processes that require changes in the shape of the cell, such as locomotion and phagocytosis. In some cells, cytoskeletal microfilaments appear to be linked indirectly through the plasma membrane to peripheral proteins on the outer surface of the cell (fig. 17.23). Among the cell surface proteins connected to this network is fibronectin, a glycoprotein believed to play a role in cell-cell interactions. The lateral diffusion of fibronectin is at least 5,000 times slower than that of freely diffusible membrane proteins. 

But there are two problems with this argument as an explanation for the origin of eukaryotes, rather than the process of phagocytosis itself. First, the key assumption is that prokaryotes are typically subsaturated with ATP, whereas eukaryotic cells are somehow not - that compartmentalisation was... 

Endocytosis — A process in which a substance gains entry into a eukaryotic cell without passing through the cell membrane. In this process particles (phagocytosis) or droplets (pinocytosis) are accumulated at the cell surface and enclosed by the cell membrane. The so-formed - vesicles are then delivered into the cell. Opposite process -> exocytosis. Endo- and exocytosis are fundamental processes of membrane fusion in living cells. See also - membrane. 

Phagocytosis — One form of -> endocytosis. The incorporation of solid particles into a eukaryotic cell via the formation of cell - vesicles. 

Actin. This is one of the most important components in the cytoskeletal architecture, and in the movement of cytoplasm in eukaryotic cells. In addition to muscle contraction, actin is involved in cellular processes such as phagocytosis, secretion, cell migration, and the maintenance of cell shape. A recent report shows that a mammalian cell arginine-specific ADP-ribosyl transferase can ADP-ribosylate actin molecules, suggesting that this could be a regulatory mechanism in the above cellular functions (Terashima et al., 1992). 

Phagocytosis. Process by which relatively large particles, e.g., bacterial cells, are internalized by certain eukaryotic cells. 

Were bacteria incapable of acquiring symbionts The assumption that only eukaryotes possessed a cytoskeleton and were therefore capable of phagocytosis had been a chief reason for postulating the archezoan host in the first place. As Cavalier-Smith (1987b, p. 56) put it forcefully, it is only the existence of such fully eukaryotic phagotrophs that makes a symbiotic origin of mitochondria mechanistically plausible no bacteria, not even predatory ones, can take up or harbor other living cells in their cytoplasm, and to... 

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