The cell wall is an extremely important component of plant, fungi and bacterial cells. As you can see in the diagram above the cell wall coats the cell, providing structural support and protection from the elements.

An important detail of the cell wall is that it is fully permeable, meaning, unlike the plasma membrane, it has no control of what exits or enters the cell.

Another important characteristic is its composition:

• Plant Cell walls: are made of Cellulose
• Fungi Cell walls: are made of chitin   
• Bacteria cell walls: are made of Murein

The cell wall provides support, prevents expansion of the cell and allows water and dissolved substances to pass freely though it.

Cell Wall

This is not considered an organelle