Vacuoles are organelles found in cells that store solutions or materials. The cell can phagocytoze, or engulf, solutions that have been created and are being stored or excreted. Vacuoles are simply chambers surrounded by a membrane, which prevents the cytosol from being exposed to the contents. Only certain molecules can pass through vacuoles because they are surrounded by semi-permeable membranes.
Vacuoles include a wide variety of membrane-bound sacs. Membranes are composed of phospholipids, but each organism uses slightly different phospholipids. Molecular transport and structure are accomplished by proteins embedded in membranes. It is possible to hold different materials in different vacuoles thanks to different combinations of these proteins.
Genes dictate which proteins embed in the membrane of the vacuole in each organism, allowing different molecules to pass through and giving the vacuoles different properties. In most plant cells, vacuoles store water and provide a variety of functions. As animals don’t use their vacuoles for rigidity, they use them to store a variety of products and to exocytose and endocytose.
Functions of a Vacuole
The majority of the cell is occupied by a large vacuole in plants. Tonoplasts surround this vacuole, a type of cytoplasmic membrane that stretches and fills itself with a solution called cell sap. Furthermore, protons from the cytosol fill the vacuole, creating an acidic environment within the cell. This chemical gradient can then be used by the vacuole to transport materials in and out of the vacuole, known as proton motive force. Water and other molecules are also involved in this process.
Plants use their vacuoles for a second function that is of utmost importance. If the vacuole is completely filled with water, it can become pressurized and exert a force on the cell walls. Even though the force in each cell is small, the turgor pressure allows the cells to create a form and withstand wind, rain and hail. Even though woody plants create proteins and fibers that help them stand tall, many non-woody plants can reach several feet in height solely through turgor pressure.
While this is an efficient way for plants to structure themselves, they will droop when the pH balance is off, or if they don’t receive enough water. Make sure your houseplants have water if they seem to be drooping. Within a few hours, they can go from wilted to turgid. Check the pH of the soil if that doesn’t work. Water and nutrients cannot be taken up by the roots without the right conditions, and the plant wilts as a result. The plant will stiffen up right away if the pH is changed.
Endocytosis and Exocytosis
Vacuoles are used whenever a large amount of substance is taken in through endocytosis or excreted through exocytosis. Plant and animal cells take in substances and store them separately from the cytosol. It may be because the substances are reactive, in which case they will cause unwanted reactions. It could also be that the substances are too large and would interfere with cellular processes.
The lysosome is a vesicle used for digesting substances. It is possible for these lysosomes to fuse to form a large, acid-digesting vesicle that can digest nutrients and transfer them to the cytosol or other organelles. The process is known as endocytosis, and it varies from cell type to cell type.
Cells that function as secretory cells must produce and excrete large amounts of different substances. In the endoplasmic reticulum, substances are synthesized, modified, and labeled for distribution by the Golgi apparatus. Vesicles can then be formed from the substances. Vesicles travel into the cytoplasm and merge into a larger vacuole before being excreted. Exocytosis is the process of removing cells from the body.
In different cells, and even within the same cell, the vacuoles that carry different substances vary in structure. Many different functions can be performed by vacuoles in an animal cell. This is an example of an animal cell and its vacuoles, the smaller unlabeled spheres are vesicles. As soon as they fuse together, they would also be considered vacuoles.
Other Storage Functions
There are many types of molecules that can be stored in vacuoles. In fat cells, for instance, specialized vacuoles store lipids in large quantities. A single cell can store a lot of fat, which organisms can use when resources are limited. Due to the expandability of the vacuole, an organism can gain or lose weight without creating or losing too many cells.
Often, organisms’ vacuoles are used to create entire ecosystems in which symbiotic organisms can coexist. In corals, algae live in vacuoles within the polyps where they are eaten through endocytosis. By doing so, the coral is able to gain oxygen and nutrients from the algae.
Related Biology Terms
- Vesicle – A smaller version of a membrane-bound vacuole, many of which can converge to make a vacuole.
- Lysosome – A special vesical containing digestive enzymes.
- Exocytosis – The process of excreting material from the cell.
- Endocytosis – The process of taking materials into the cell.
A vacuole is an organelle found in plant and fungal cells that functions as a storage space for water, nutrients, and waste materials. It is surrounded by a membrane called the tonoplast, which separates the contents of the vacuole from the rest of the cell.
Vacuoles play a critical role in maintaining the structural integrity of plant cells, as they help to regulate the osmotic pressure within the cell. They also store important compounds such as pigments, toxins, and carbohydrates, and can act as a defense mechanism against herbivores by storing toxic compounds.
In fungal cells, vacuoles are involved in several key processes such as maintaining cellular pH, storing nutrients and energy, and regulating the transport of molecules in and out of the cell.
In plant cells, there are two main types of vacuoles: the central vacuole, which is typically larger and more prominent, and the smaller storage vacuoles, which are found in various parts of the cell. In fungal cells, there are also several types of vacuoles, including the lytic vacuole, which is involved in cell growth and differentiation, and the contractile vacuole, which is involved in regulating water balance.
While vacuoles are primarily found in plant and fungal cells, there are some vacuole-related disorders that can affect human health. For example, defects in the lysosomal vacuole can lead to lysosomal storage disorders such as Tay-Sachs disease, while defects in the autophagic vacuole can lead to neurodegenerative diseases such as Parkinson’s and Alzheimer’s.