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The anthocyanin-storing vacuoles of Rhoeo spathacea, a spiderwort, in cells that have plasmolyzed. Most mature plant cells have one large vacuole that typically occupies more than 30% of the cell's volume, and that can occupy as much as 80% of the volume for certain cell types and conditions. [21] Strands of cytoplasm often run through the vacuole.
Some cells, most notably Amoeba, have contractile vacuoles, which can pump water out of the cell if there is too much water. The vacuoles of plant cells and fungal cells are usually larger than those of animal cells. Vacuoles of plant cells are surrounded by a membrane which transports ions against concentration gradients.
By scientific convention, the term lysosome is applied to these vesicular organelles only in animals, and the term vacuole is applied to those in plants, fungi and algae (some animal cells also have vacuoles). Discoveries in plant cells since the 1970s started to challenge this definition. Plant vacuoles are found to be much more diverse in ...
The cells of meristematic tissue are similar in structure and have a thin and elastic primary cell wall made of cellulose. They are compactly arranged without inter-cellular spaces between them. Each cell contains a dense cytoplasm and a prominent cell nucleus. The dense protoplasm of meristematic cells contains very few vacuoles.
The contractile vacuole is predominant in species that do not have a cell wall, but there are exceptions (notably Chlamydomonas) which do possess a cell wall. Through evolution , the contractile vacuole has typically been lost in multicellular organisms, but it still exists in the unicellular stage of several multicellular fungi , as well as in ...
Organelles (literally "little organs") are usually membrane-bound structures inside the cell that have specific functions. Some major organelles that are suspended in the cytosol are the mitochondria, the endoplasmic reticulum, the Golgi apparatus, vacuoles, lysosomes, and in plant cells, chloroplasts.
Plant cells have a large central vacuole in the center of the cell that is used for osmotic control and nutrient storage. Contractile vacuoles are found in certain protists, especially those in Phylum Ciliophora. These vacuoles take water from the cytoplasm and excrete it from the cell to avoid bursting due to osmotic pressure.
In ciliates there is a specialized groove or chamber in the cell where phagocytosis takes place, called the cytostome or mouth. As in phagocytic immune cells, the resulting phagosome may be merged with lysosomes (food vacuoles) containing digestive enzymes, forming a phagolysosome.