Vacuoles

A vacuole is a membrane-bound space present within the cytoplasm of a cell. Rather than being solid, it is an enclosed pocket that holds a variety of contents, including water, sap, excretory products, and other substances that the cell does not need.

The membrane around it

A vacuole is bounded by a single membrane, and this membrane is given a special name — the tonoplast.

Vacuoles in plant cells

In plant cells the vacuole is a very prominent feature:

• It can take up as much as ninety per cent of the total volume of the cell.
• The tonoplast actively helps to move a number of ions and other materials into the vacuole, and it does so against their concentration gradients.
• Because of this active transport, the concentration of these substances is considerably higher inside the vacuole than in the surrounding cytoplasm.

Specialised vacuoles in other organisms

Vacuoles also perform particular tasks in certain organisms: …