vacuole

A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Tonoplast is a membrane of a vacuole.

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. The organelle has no basic shape or size; its structure varies according to the needs of the cell.

The function and importance of vacuoles varies greatly 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. In general, the functions of the vacuole include:

Isolating materials that might be harmful or a threat to the cell:

• Containing waste products
• Containing water in plant cells
• Maintaining internal hydrostatic pressure or turgor within the cell
• Maintaining an acidic internal pH
• Containing small molecules
• Exporting unwanted substances from the cell
• Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole
• In seeds, stored proteins needed for germination are kept in 'protein bodies', which are modified vacuoles.