Vacuole

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Plant Cell Vacuoles
Vacuoles are membrane-bound sacs within the cytoplasm of a cell that function in several different ways. In mature plant cells, vacuoles tend to be very large and are extremely important in providing structural support, as well as serving functions such as storage, waste disposal, protection, and growth. Many plant cells have a large, single **central vacuole** that typically takes up most of the room in the cell (80 percent or more). Vacuoles in animal cells, however, tend to be much smaller, and are more commonly used to temporarily store materials or to transport substances = = = = = = =Vacuole= A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. Vacuoles tend to be large in plant cells and play a role in turgor pressure. When a plant is well-watered, water collects in cell vacuoles producing rigidity in the plant. Without sufficient water, pressure in the vacuole is reduced and the plant wilts. http://www.cellsalive.com/cells/vacuole.htm The cell sap vacuole in plants is much larger than animals. In addition to storing important substances, it also helps support the plant. The pressure of water filling the cell sap vacuole pushes out against the cell wall. This gives the wall enough strength to hold up fairly large gree (non-woody) plants. We all know the first indication that we are not giving our house plants enough water. They start to droop or wilt. Now you know why, so keep that cell sap vacuole filled with water. http://projects.edtech.sandi.net/miramesa/Organelles/vacuole.html The vacuole is used only in plant cells. It is responsible for maintaining the shape and structure of the cell. Plant cells don't increase in size by expanding the cytosplasm, rather they increase the size of their vacuoles. The vacuole is a large vesicle which is also used to store nutrients, metabolites, and waste products.

=Vacuoles - Storage Bins to the Cells= **Vacuoles** are storage bubbles found in cells. They are found in both animal and plant cells but are much larger in plant cells . Vacuoles might store food or any variety of nutrients a cell might need to survive. They can even store waste products so the rest of the cell is protected from contamination. Eventually, those waste products would be sent out of the cell.

The structure of vacuoles is fairly simple. There is a **membrane** that surrounds a mass of fluid. In that fluid are nutrients or waste products. Plants may also use vacuoles to store water. Those tiny water bags help to support the plant. They are closely related to objects called vesicles that are found throughout the cell.

In plant cells, the vacuoles are much larger than in animal cells. When a plant cell has stopped growing, there is usually one very large vacuole. Sometimes that vacuole can take up more than half of the cell's volume. The vacuole holds large amounts of water or food. Don't forge that vacuoles can also hold the plant waste products. Those waste products are slowly broken into small pieces that cannot hurt the cell. Vacuoles hold onto things that the cell might need, just like a backpack.

Vacuole
A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. Vacuoles tend to be large in plant cells and play a role in turgor pressure. When a plant is well-watered, water collects in cell vacuoles producing rigidity in the plant. Without sufficient water, pressure in the vacuole is reduced and the plant wilts.http://www.cellsalive.com/cells/vacuole.htm =Vacuoles - Storage Bins to the Cells= **Vacuoles** are storage bubbles found in cells. They are found in both animal and plant cells but are much larger in [|plant cells]. Vacuoles might store food or any variety of nutrients a cell might need to survive. They can even store waste products so the rest of the cell is protected from contamination. Eventually, those waste products would be sent out of the cell.

The structure of vacuoles is fairly simple. There is a **membrane** that surrounds a mass of fluid. In that fluid are nutrients or waste products. Plants may also use vacuoles to store water. Those tiny water bags help to support the plant. They are closely related to objects called vesicles that are found throughout the cell.

In plant cells, the vacuoles are much larger than in animal cells. When a plant cell has stopped growing, there is usually one very large vacuole. Sometimes that vacuole can take up more than half of the cell's volume. The vacuole holds large amounts of water or food. Don't forge that vacuoles can also hold the plant waste products. Those waste products are slowly broken into small pieces that cannot hurt the cell. Vacuoles hold onto things that the cell might need, just like a backpack.

=Helping with Support= Vacuoles also play an important role in plant structure. Plants use [|cell walls] to provide support and surround cells. The size of that cell may still increase or decrease depending on how much water is present. Plant cells do not shrink because of changes in the amount of [|cytoplasm]. Most of a plant cell's volume depends on the material in vacuoles.

Those vacuoles gain and lose water depending on how much water is available to the plant. A drooping plant has lost much of its water and the vacuoles are shrinking. It still maintains its basic structure because of the cell walls. When the plant finds a new source of water, the vacuoles are refilled and the plant regains its structure.

In general,[|vacuole] functions include:
 * Isolating materials that might be harmful or a threat to the cell
 * Containing waste products
 * Maintaining internal [|hydrostatic pressure] or [|turgor] within the cell
 * Maintaining an [|acidic] internal [|pH]
 * Containing small molecules
 * Exporting unwanted substances from the cell
 * Vacuoles** also play a major role in faginess maintaining a balance between [|biogenesis] (production) and degradation (or turnover), of many substances and cell structures. Vacuoles store food and other materials needed by a cell. They also aid in destruction of invading [|bacteria] or of misfolded proteins that have begun to build up within the cell. The vacuole is a major part in the plant cell.

http://www.biology4kids.com/files/cell_vacuole.html

Vacuoles are bounded by a single membrane. Young plant cells often contain many small vacuoles, but as the cells mature, these unite to form a large **central vacuole**. Vacuoles serve several functions, such as Plant cells avoid bursting in [|hypotonic] surroundings by their strong cell walls. These allow the build-up of **turgor** within the cell. Loss of turgor causes wilting.
 * storing foods (e.g., proteins in seeds)
 * storing wastes
 * [|storing malic acid in CAM plants]
 * storing various ions (e.g., calcium, sodium, iron) which, among other functions, helps to
 * maintain turgor in the cell.

=Vacuole=

A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. In animal cells, vacuoles are generally small.

Vacuoles tend to be large in plant cells and play a role in turgor pressure. When a plant is well-watered, water collects in cell vacuoles producing rigidity in the plant. Without sufficient water, pressure in the vacuole is reduced and the plant wilts.http://www.cellsalive.com/cells/vacuole.htm



http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PlantCell.html

A vacuole is a sac bound to a membrane that takes part in digestion and the release of cellular waste products. Vacuoles are found in mostly plant cells. They play a role in __turgor pressure__. Water collects in cell vacuoles producing rigidity in the well-watered plant. Without enough water, pressure in the vacuole is reduced and the plant wilts.

The central vacuole in plant cells (see Figure 1) is enclosed by a membrane termed the **tonoplast**, an important and highly integrated component of the plant internal membrane network (**endomembrane**) system. This large vacuole slowly develops as the cell matures by fusion of smaller vacuoles derived from the endoplasmic reticulum and Golgi apparatus. Because the central vacuole is highly selective in transporting materials through its membrane, the chemical palette of the vacuole solution (termed the **cell sap**) differs markedly from that of the surrounding cytoplasm. For instance, some vacuoles contain pigments that give certain flowers their characteristic colors. The central vacuole also contains plant wastes that taste bitter to insects and animals, while developing seed cells use the central vacuole as a repository for protein storage. Among its roles in plant cell function, the central vacuole stores salts, minerals, nutrients, proteins, pigments, helps in plant growth, and plays an important structural role for the plant. Under optimal conditions, the vacuoles are filled with water to the point that they exert a significant pressure against the cell wall. This helps maintain the structural integrity of the plant, along with the support from the cell wall, and enables the plant cell to grow much larger without having to synthesize new cytoplasm. In most cases, the plant cytoplasm is confined to a thin layer positioned between the plasma membrane and the tonoplast, yielding a large ratio of membrane surface to cytoplasm. The structural importance of the plant vacuole is related to its ability to control **turgor pressure**. Turgor pressure dictates the rigidity of the cell and is associated with the difference between the osmotic pressure inside and outside of the cell. Osmotic pressure is the pressure required to prevent fluid diffusing through a semipermeable membrane separating two solutions containing different concentrations of solute molecules. The response of plant cells to water is a prime example of the significance of turgor pressure. When a plant receives adequate amounts of water, the central vacuoles of its cells swell as the liquid collects within them, creating a high level of turgor pressure, which helps maintain the structural integrity of the plant, along with the support from the cell wall. In the absence of enough water, however, central vacuoles shrink and turgor pressure is reduced, compromising the plant's rigidity so that wilting takes place. Plant vacuoles are also important for their role in molecular degradation and storage. Sometimes these functions are carried out by different vacuoles in the same cell, one serving as a compartment for breaking down materials (similar to the lysosomes found in animal cells), and another storing nutrients, waste products, or other substances. Several of the materials commonly stored in plant vacuoles have been found to be useful for humans, such as opium, rubber, and garlic flavoring, and are frequently harvested. Vacuoles also often store the pigments that give certain flowers their colors, which aid them in the attraction of bees and other pollinators, but also can release molecules that are poisonous, odoriferous, or unpalatable to various insects and animals, thus discouraging them from consuming the plant.



- Membrane-bound sacs for storage, digestion, and waste removal - Contains water solution - Contractile vacuoles for water removal (in unicellular organisms) ||
 * [[image:http://library.thinkquest.org/12413/img/vacuoles.jpg width="134" height="134" caption="Vacuoles"]] || **Vacuoles**

A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. In animal cells, vacuoles are generally small.

Vacuoles tend to be large in plant cells and play a role in turgor pressure. When a plant is well-watered, water collects in cell vacuoles producing rigidity in the plant. Without sufficient water, pressure in the vacuole is reduced and the plant wilts.

The vacuole is used only in plant cells. It is responsible for maintaining the shape and structure of the cell. Plant cells don't increase in size by expanding the cytosplasm, rather they increase the size of their vacuoles. The vacuole is a large vesicle which is also used to store nutrients, metabolites, and waste products. The pressure applied by the vacuole, called turgor, is necessary to maintain the size of the cell. If turgor is lost the cell becomes flaccid. The vacuole typically is 50% of the volume of the cell, yet it can take up to 95% of the cell!

In general, **vacuole** functions include: Most mature [|plant cells] have one or several **vacuoles** that typically occupy more than 30% of the cell's volume, and that can occupy as much as 90% of the volume for certain cell types and conditions.[|[1]] A vacuole is surrounded by a membrane called the **tonoplast**. Transport of [|protons] from cytosol to vacuole aids in keeping cytoplasmic [|pH] stable, while making the vacuolar interior more acidic, allowing degradative enzymes to act. Although having a large central vacuole is the most common case, the size and number of vacuoles may vary in different tissues and stages of development. Cells of the [|vascular cambium], for example, have many small vacuoles in the winter, and one large one in the summer. Aside from storage, the main role of the central vacuole is to maintain [|turgor] pressure against the [|cell wall]. Proteins found in the tonoplast control the flow of water into and out of the vacuole through [|active transport], pumping [|potassium] (K+) [|ions] into and out of the vacuolar interior. Due to [|osmosis], water will diffuse into the vacuole, placing pressure on the cell wall. If water loss leads to a significant decline in turgor pressure, the [|cell] will [|plasmolyse]. Turgor pressure exerted by vacuoles is also helpful for cellular elongation: as the cell wall is partially degraded by the action of [|auxins], the less rigid wall is expanded by the pressure coming from within the vacuole. Vacuoles can help some plant cells to reach considerable size. Another function of a central vacuole is that it pushes all contents of the cell's cytoplasm against the cellular membrane, and thus keeps the [|chloroplasts] closer to light.
 * Isolating materials that might be harmful or a threat to the cell
 * Containing waste products
 * Maintaining internal [|hydrostatic pressure] or [|turgor] within the cell
 * Maintaining an [|acidic] internal [|pH]
 * Containing small molecules
 * Exporting unwanted substances from the cell
 * Vacuoles** also play a major role in faginess maintaining a balance between [|biogenesis] (production) and degradation (or turnover), of many substances and cell structures. Vacuoles store food and other materials needed by a cell. They also aid in destruction of invading [|bacteria] or of misfolded proteins that have begun to build up within the cell. The vacuole is a major part in the plant cell.