In plant and fungal cells, as well as some protist, animal, and bacterial cells, a vacuole is a membrane-bound organelle that can be found in the cell membrane. Vacuoles are essentially closed compartments that are filled with water that contains inorganic and organic molecules in solution, including enzymes, albeit they may also contain solids that have been absorbed in the water. Multiple membrane vesicles join together to form vacuoles, which are essentially just larger versions of their smaller counterparts. The organelle does not have a fixed shape or size; rather, its structure is determined by the needs of the cell.
Spallanzani (1776) was the first to identify contractile vacuoles (“stars”) in protozoa, but he mistook them for respiratory organs at the time. Vacuoles were named by Dujardin (1841) for their “stars.” Schleiden used the term “plant cell” in 1842 to separate the structure containing the cell sap from the remainder of the protoplasm of the plant cell. De Vries coined the term “tonoplast” to describe the membrane that surrounds the vacuole.
Uses of vacuoles
It is important to note that the role and significance of vacuoles differ substantially depending on the kind of cell in which they are found, with vacuoles being far more prominent in the cells of plants, fungi, and certain protists than those of mammals and bacteria. In general, the vacuole performs the following functions:
- The first step is to isolate components that could be toxic or pose a hazard to the cell.
- It is a container for waste products.
- Plant cells that are capable of containing water.
- Keeping the internal hydrostatic pressure or turgor of the cell constant within the cell.
- Keeping the internal pH of the body at an acidic level.
- Having a high concentration of tiny molecules.
- The cell’s ability to remove undesired chemicals from the environment.
- Because of the pressure exerted by the central vacuole, plants are able to maintain structural elements such as leaves and flowers.
- The germinating plant or its organs (such as leaves) can develop very quickly when the plant’s size increases, requiring only a small amount of water.
- In seeds, protein bodies, which are modified vacuoles, are used to store proteins that are required for germination.
Furthermore, vacuoles play a critical role in autophagy, which is responsible for maintaining a balance between the biogenesis (creation) and the destruction (or turnover) of a wide range of chemicals and cell structures in some species. They also contribute to the lysis and recycling of misfolded proteins that have begun to accumulate within the cell. The vacuole, according to Thomas Boller and others, is involved in the killing of invading bacteria, while Robert B. Mellor postulated that organ-specific forms play a role in ‘housing’ symbiotic bacteria in the vacuole. With respect to protists, vacuoles also serve the added role of storing food that has been absorbed by the organism as well as assisting in the digestion and waste disposal processes for the cell. When it comes to animal cells, vacuoles have a primarily supporting role, assisting in the bigger processes of exocytosis and endocytosis, respectively. Animal vacuoles are not only smaller in size than their plant counterparts, but they are also more numerous. In addition, there are animal cells that do not contain any vacuoles. Exocytosis is defined as the process by which proteins and lipids are extruded from the cell. In the Golgi apparatus, these components are absorbed and stored in secretory granules before being transported to the cell membrane and secreted into the extracellular environment. The function of vacuoles in this context is that they serve as storage compartments for proteins and lipids that are transported out of the cell and disposed of by the cell’s extracellular environment. Endocytosis is the polar opposite of exocytosis and can manifest itself in a variety of ways. Phagocytosis (also known as “cell eating”) is a process in which bacteria, dead tissue, and other bits of material visible under a microscope are ingested by cells and digested. As soon as the substance comes into touch with the cell membrane, it begins to invaginate it. It is necessary to pinch off the invagination in order to preserve the swallowed material in the membrane-enclosed vacuole as well as the integrity of the cell membrane. While pinocytosis (“cell drinking”) and phagocytosis (“cell eating”) are both similar processes, the distinction is that the substances consumed are in solution and hence cannot be seen under a microscope. Phagocytosis and pinocytosis are both processes that take place in conjunction with lysosomes, which are responsible for completing the breakdown of the material that has been ingested. Several mammalian species’ vacuoles have been shown to contain Salmonella, which has been shown to survive and multiply there. In the Viridiplantae, the vacuole is thought to have evolved multiple times independently of one another.
Conclusion
The primary role of vacuoles is to store numerous substances and molecules; in this way, they can be thought of as the storage unit for the cell. The following are some of the most important vacuole functions, many of which are related to storing materials that the cell will require later on or that can harm the cell and must therefore be removed:
- Remove and store the garbage created by autophagy as it occurs (when part of the cell is broken down due to age or damage)
- Remove and store potentially dangerous foreign substances so that they do not damage the cell.
- Keep water in a safe place.
- Nutrients like as lipids, proteins, and carbohydrates are kept in reserve.