3.  A vacuole is a large single membrane-bound (tonoplast) organelle which is present in all plant and fungal, animal, bacterial cells and some protists.  Vacuoles are an integral part of a cell’s endomembrane system.  Vacuolar membrane is selective in transporting solutes.  Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain cases they may contain solids which have been engulfed.  Vacuoles are formed by the fusion of multiple membrane vesicles and are effectively just larger forms of these.  The organelle has no basic shape or size; its structure varies according to the needs of the cell.

6.  The function and significance of vacuoles varies according to the type of cell in which they are present, having much greater prominence in the cells of plants, fungi and certain protists than those of animals and bacteria.  Vacuole Isolate materials that might be harmful or a threat to the cell  Contain waste products  Contain water in plant cells  Maintain internal hydrostatic or turgor within the cell  Maintain an acidic internal pH  Export unwanted substances from the cell  Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole

7.  In seeds, stored proteins needed for germination are in 'protein bodies', which are modified vacuoles.  Vacuoles also play a major role in autophagy, maintaining a balance between biogenesis (production) and degradation (or turnover), of many substances and cell structures in certain organisms.  They also aid in the lysis and recycling of misfolded proteins in the cell.  Vacuole participates in the destruction of invading bacteria.  Specific forms of vacuoles have a role in 'housing' symbiotic bacteria.  In protists, vacuoles have the additional function of storing food which has been absorbed by the organism and assisting in the digestive and waste management process for the cell

12.  Large vacuoles are found in three genera of filamentous sulfur bacteria, the Thioploca, the Beggiatoa, and Thiomargarita.  The cytosol is extremely reduced in these genera and the vacuole can occupy between 40–98% of the cell.  The vacuole contains high concentrations of nitrate ions and is therefore thought to be a storage organelle  Gas vacuoles, which are freely permeable to gas, are present in some species of Cyanobacteria. They allow the bacteria to control their buoyancy.

13.  Mature plant cells have one large vacuole that occupies 70-80% of the volume for certain cell types.  Vacuole is surrounded by a membrane called the tonoplast (Gk. tono, meaning “stretching”, “tension”, Gk plastós, molded). A membrane, involved in regulating the movements of ions around the cell, and isolating materials that might be harmful or a threat to the cell  Transport of protons from the cytosol to the vacuole stabilizes cytoplasmic pH, while making the vacuolar interior more acidic creating a proton motive force which the cell can use to transport nutrients into or out of the vacuole. The low pH of the vacuole also allows degradative enzymes to act.  The size and number of vacuoles may vary in different tissues and stages of development. For example, developing cells in the meristems contain small provacuoles and cells of the vascular cambium have many small vacuoles in the winter and one large one in the summer.  The main role of the central vacuole is to maintain turgor pressure against the cell wall.

14.  Proteins (aquaporins) control the flow of water into and out of the vacuole through active transport, pumping K + into and out of the vacuole.  By osmosis, water will diffuse into the vacuole and exerts pressure on the cell wall. If water loss leads to a significant decline in turgor pressure, the cell will plasmolysed.  Turgor pressure exerted by vacuoles is also required for cellular elongation: as the cell wall is partially degraded by the action of expansins. Turgor pressure exerted by the vacuole is also essential in supporting plants in an upright position.  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.  Most plants store chemicals in the vacuole that react with chemicals in the cytosol.  If the cell is broken, by a herbivore or other wise, then the two chemicals can react forming toxic chemicals.  In garlic, allin and the enzyme allinase are normally separated but form allicin if the vacuole is broken. A similar reaction is responsible for the production of syn-propanethyl oxide when onions are cut

15. Peripheral chloroplasts

17.  Vacuoles in fungal cells perform similar functions to those in plants and there can be more than one vacuole per cell. In yeast cells the vacuole is a dynamic structure that can rapidly modify its morphology.  They are involved in many processes including the homeostasis of cell pH and the concentration of ions, osmoregulation, storing amino acids and polyphosphate and degradative processes.  Toxic ions, such as strontium (Sr 2+ ), cobalt (Co 2+ ), and lead (Pb 2+ ) are transported into the vacuole to isolate them from the rest of the cell

18.  In animal cells, vacuoles perform exocytosis and endocytosis.  Animal vacuoles are smaller but greater in number. There are also animal cells that do not have any vacuoles  Via exocytosis vacuoles are simply storage vesicles which transport the selected proteins and lipids to the extracellular environment of the cell.  Endocytosis is the reverse of exocytosis and can occur in a variety of forms. Phagocytosis ("cell eating") is the process by which bacteria, dead tissue, or other material are engulfed by cells. Pinocytosis ("cell drinking") allows the substances ingested are in solution.  Salmonella is able to survive and reproduce in the vacuoles of several mammals species after being engulfed