A central vacuole is a eukaryotic cell organelle, specific for plant and fungal cells.
Structure of the central vacuole
A central vacuole is a single large structure, varying in shape depending on the cell, delimited by a lipid membrane called a tonoplast. The vacuole concentrates 80-90% of the volume and weight of the plant cell. It mainly contains water, but also organic molecules such as carbohydrates, ions, pigments…
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Role of the central vacuole
The central vacuole has above all a role of maintaining cellular homeostasis, that is to say it allows maintenance of the right concentrations of elements in the cytoplasm, by selectively storing elements within its membrane.
It also plays an important role in the turgor of plant cells, by ensuring sufficient pressure inside the cell, to maintain rigidity of certain anatomical structures (stem).
Central vacuoles could be isolated from adult plant cells by the following process: plant protoplasts are first obtained by treating certain tissues (flower petals, fungal hyphae) with mixtures of pectinases and cellulases or else with chitinases. Cell walls are hydrolyzed by these enzymes and cell protoplasms are released into the medium (protoplasts). These protoplasts are gently dilacerated and the vacuoles can be collected by differential density gradient centrifugation. The enzymatic activities associated with these isolated vacuolar fractions are essentially hydrolytic activities: proteinases, exopeptidases, RNAses, DNAses, phosphatases, phosphodiesterases, acetyl esterases, amylases, glucosidases, galactosidases, mannosidases, etc. These enzymatic characteristics clearly relate plant vacuoles to the lysosomes of animal cells.
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