The contractile vacuole and its function

This article acquaints the reader with the structure of the simplest organisms, namely, focuses on the structure of the contractile vacuole, which performs the excretory (and not only) function, tells about the importance of the protozoa, and describes the ways of their existence in the environment.

The contractile vacuole. The concept of

Vacuole (from the French vacuole, from the Latin word vacuus - empty), spherical in shape small cavities in plant and animal cells or unicellular organisms. The contractile vacuoles are primarily distributed among the simplest organisms that live in freshwater, for example among protists such as amoeba proteus and infusoria shoe, which received such an original name because of the shape of the body, similar to the shape of the sole of the shoe. In addition to the listed protozoa, identical structures were also found in the cells of various freshwater sponges that belong to the Badagov family.

The structure of the contractile vacuole. Its features

The contractile vacuole is a membrane organoid that discharges excess fluid from the cytoplasm. The localization and structure of this apparatus varies among different microorganisms. From the complex of vesicular or tubular vacuoles called spongies, the fluid enters the contractile vacuole. Due to the constant operation of this system, a stable cell volume is maintained. The protozoans have contractile vacuoles, which are a device that regulates the osmotic pressure, and also serves to isolate decay products from the body. The body of the protozoa consists of only one cell, which, in turn, carries out all necessary vital functions. Representatives of this sub-kingdom, such as infusoria shoe, amoeba vulgaris, other unicellular ones possess all the properties of an independent organism.

The role of protozoa

The cell performs all vital functions: liberation, respiration, irritability, movement, reproduction, metabolism. Protozoa are widespread everywhere. The largest number of species lives in marine and fresh waters, many inhabit moist soil, can affect plants, live in the bodies of multicellular animals and humans. In nature protozoa perform a sanitary role, they also participate in the circulation of substances, are food for many animals.

The contractile vacuole in amoeba vulgaris

Amoeba vulgaris - a representative of the class of rhizome, does not, unlike other representatives of the permanent form of the body. Movement is carried out using the pseudopods. Now let's look at the function of the contractile vacuole in amoeba. This is the regulation of the level of osmotic pressure inside its cells. It can form in any part of the cell in the amoeba proteus . Through the outer membrane, water from the environment enters osmotically. The concentration of dissolved substances in the amoeba cell is higher than in the environment. Thus, a pressure difference is created inside the cell of the simplest and beyond. Functions of the contractile vacuole in amoeba are a kind of evacuating apparatus that removes excess water from the cell of the simplest organism. Dispose of the accumulated liquid of amoeba proteus into the environment in any part of the body surface.

This function of the contractile vacuole is acceptable for the simplest organisms living in freshwater. Parasitic and marine forms that live in an environment where the osmotic pressure is higher than in fresh water, these primitive apparatuses are reduced very rarely or usually absent. Around the contractile vacuole in the simplest organisms, mitochondria are concentrated, delivering energy to perform osmotic work.

In addition to osmoregulatory, it performs the function of breathing in life, since as a result of osmosis the incoming water delivers the oxygen dissolved in it. What is the function of the contractile vacuole? It also performs the excretory function, namely, together with water, the metabolic products are released into their environment.

Breathing, excretion, osmoregulation in the infusoria of the shoe

The body of the protozoans is covered with a dense shell, which has a constant shape. It feeds both bacteria and algae, including some protozoa. The organism of the infusoria has a more complex structure than the amoeba. In the cage of the shoe, two contractile vacuoles are located in front and behind. In this apparatus, a reservoir and several small tubules are distinguishable. The contractile vacuoles are constantly found, thanks to this structure (from microtubules), at a constant place in the cell.

The main function of the contractile vacuole in the vital activity of this protozoan representative is osmoregulation, and it also removes excess water from the cell that penetrates the cell through osmosis. First, swelling of the leading channels occurs, then water from them is pumped into a special reservoir. The reservoir is reduced, separated from the leading channels, through the pores, water is ejected outward. In the cage of the infusoria there are two contractile vacuoles, which, in turn, act in antiphase. Due to the operation of two such devices, a continuous process is provided. In addition, water continuously circulates through the activity of contractile vacuoles. They are contracted in turn, and the frequency of contractions depends on the ambient temperature.

So, at room temperature (+18 - +20 degrees Celsius), the frequency of contractions of the vacuoles is, according to some data, 10-15 seconds. And given that the natural environment of the shoe is any fresh water with standing water and the presence of decomposing organic substances in it, the temperature of this medium varies by several degrees depending on the season and, therefore, the frequency of contractions can reach 20-25 seconds. In an hour the contractile vacuole of the simplest organism is able to throw out water from the cell in an amount. Commensurate with its size. They accumulate nutrients, undigested food residues, end products of metabolism, oxygen and nitrogen can also be detected.

Wastewater treatment by protozoa

The influence of protists on the circulation of substances in nature is of great importance. In reservoirs, due to the descent of sewage, bacteria multiply in large numbers. As a result, various protozoan organisms appear that use these bacteria as food and thus contribute to the natural purification of water bodies.

Conclusion

Despite the simple structure of these unicellular organisms, the body of which consists of a single cell, but fulfills the functions of the whole organism, surprisingly adapted to the environment. This can be observed even on the example of the structure of the contractile vacuole. To date, the great importance of the simplest in nature and their participation in the circulation of substances has already been proven.