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A vacuole (/ ˈ v æ k juː oʊ l /) is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. [ 1 ] [ 2 ] Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution , though in certain cases ...
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 ...
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.
Pigments that color the cell are sometime located in the cell sap. Vacuoles can also increase the size of the cell, which elongates as water is added, and they control the turgor pressure (the osmotic pressure that keeps the cell wall from caving in). Like lysosomes of animal cells, vacuoles have an acidic pH and contain hydrolytic enzymes.
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 cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function.The name organelle comes from the idea that these structures are parts of cells, as organs are to the body, hence organelle, the suffix -elle being a diminutive.
For example, the membrane around peroxisomes shields the rest of the cell from peroxides, chemicals that can be toxic to the cell, and the cell membrane separates a cell from its surrounding medium. Peroxisomes are one form of vacuole found in the cell that contain by-products of chemical reactions within the cell.
Structure of a plant cell. Plant cells are the cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae.Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids with the capability to perform photosynthesis and store starch, a large vacuole that regulates turgor pressure, the absence of flagella or ...