What Is the Meaning of Contractile Vacuole

Posted by on April 17, 2022

Nitrogen-containing waste, which is formed during work in the cell, is excreted by means of contractile vacuoles. These food masses appear to be trapped in a small area that contains liquid called vacuoles. The contractile vacuole is a special type of vacuole that regulates the amount of water in a cell. In freshwater environments, the concentration of solutes is hypotonic, lower outside the cell than in the cell. Under these conditions, osmosis causes the accumulation of water from the external environment in the cell. The contractile vacuole acts as part of a protective mechanism that prevents the cell from absorbing too much water and possibly lysing (tearing) due to excessive internal pressure. The body of the uterus consists of a very dense muscle substance, gray in color, which has an amazing contractile strength. This is done by pulsating the vacuole, which eventually bursts and directs the liquid waste outwards. The number of contractile vacuoles per cell varies by species. Amoebae have one, Dictyostelium discoideum, Paramecium aurelia and Chlamydomonas reinhardtii have two, and giant amoebae, like Chaos carolinensis, have many. The number of contractile vacuoles in each species is generally constant and is therefore used for the characterization of species in systematics.

The contractile vacuole has several structures in most cells, such as membrane folds, tubules, water channels, and small vesicles. These structures were called spongiomas; The contractile vacuole, along with the spongioma, is sometimes called the “contractile vacuole complex” (CVC). The spongioma performs several functions by transporting water into the contractile vacuole and locating and docking the contractile vacuoles in the cell. The contractile vacuole, as the name suggests, expels water from the cell by contracting. The growth (water retention) and contraction (water excretion) of contractile vacuoles are periodic. A cycle lasts several seconds, depending on the type and osmolarity of the environment. The stage at which water flows into the CV is called diastole. The contraction of the contractile vacuole and the expulsion of water from the cell are called systole. Water always flows first from outside the cell into the cytoplasm and is then moved from the cytoplasm only into the contractile vacuole for expulsion. Species that possess a contractile vacuole usually always use the organelle, even in very hypertonic environments (high concentration of solutes), because the cell tends to adjust its cytoplasm to become even more hyperosmotic than the environment. The amount of water expelled from the cell and the rate of contraction are related to the osmolarity of the environment.

In hyperosmotic environments, less water is expelled and the contraction cycle is longer. Britannica.com: Encyclopedia articles on contractile vacuoles The best understood contractile vacuoles belong to the protists Paramecium, Amoeba, Dictyostelium and Trypanosoma, to a lesser extent to the green algae Chlamydomonas. Not all species that possess a contractile vacuole are freshwater organisms; Some marine microorganisms and parasites, from the soil also have a contractile vacuole. Contractile vacuole is widespread in species that do not have a cell wall, but there are exceptions (especially chlamydomonas) that have a cell wall. During evolution, the contractile vacuole has generally been lost in multicellular organisms, but it still exists in the single-celled stage of several multicellular fungi, as well as in different types of cells in sponges (amoebocytes, pinacocytes and choanocytes). [1] In another single-celled animal called Vorticella, part of the cell became elongated and contractile. It has been implied that azidocalciums act alongside the contractile vacuole to respond to osmotic stress. They have been detected near vacuoles in Trypanosoma cruzi and have been shown to merge with vacuole when cells are exposed to osmotic stress. .