Cell wall is the outer most structure in the cell. It is not present in all types of cells.
It is present only in plant cells and bacterial cells. Hence due to this character, bacteria is sometimes classified under plant kingdom.
The cell wall is rigid structure and is made of different organic materials like peptides, chitin, lignin etc.
These walls are in general no porous and are physically dry in nature.
The cell wall being absent in animal and human cells indicates a special function and role in plant cells. So below we see the functions of cell wall.
What are the Functions of the Cell Wall
We can read the functions of cell wall in 6 points as
1.They give external protection to the cell. That is they prevent any physical damage to the inner cell structures from external forces.
2. Prevent cells from drying: The cell wall helps bacteria to tolerate intense heat of sun. If not the cell wall, the cell would dry up due to evaporation. So the cell wall prevents from desiccation of cell. Without cell wall, the cell would dry up leading to plasmolysis.
In animals this is not needed as they move away to shade or shelter to escape heat. The cell wall is so hard that bacteria are even resistant to sterilization.
3. They keep the cell clumped: Cell walls are always interlinked in plants and other multi-cellular organisms. This cell wall forms stable joints helping cell to clump to each other and stay in fixed position in the whole plant.
In animals, the cells form tissues which are attached to the skeleton system for support. These animal cells are attached to each other by cell membranes and not by cell wall.
Also see the difference between cell wall and cell membrane.
4. They give shape: Cell wall provides fixed shape to the cell. Without cell wall, the cell would have flexible shape. So the rigid and hard structure of plants is due to cell wall. Hence because of cell wall, plants might not be needing an internal skeleton like those found in humans and animals. In animals and humans the shape is due to bony skeleton. But due to cell wall the cells are clumped together to give a definite shape.
5. Manage waste matter: Many metabolites in plants are excreted by shedding of leaves or other parts. But some of the metabolites are just merged with cell wall. Hence we can see that cell wall increases in size (width) as the cell ages in plants.As the plant ages, bio-molecules like chitin, lignin are deposited into cell wall.
This way the waste material is dumped into the cell wall. In humans and animals, the waste matter is carried away by blood to the excretory organs for expulsion from the body.
6. Permeability: Cell wall though is tough and rigid is permeable to small molecules like water and carbon dioxide. This helps the movement of water within the plant without requirement of blood circulation. Of-course the main transport vessel for the conduction in plant is xylem and phloem. But cell wall permeability helps inter-cellular transport by diffusion and other processes.
Also besides, in bacteria cell wall provides flagella and pili functions. Flagella help in movement, while pili helps in genetic material exchange.
Thus cell wall performs those functions in plants which are absolutely needed due to lack of motion. And also the need to tolerate harsh climate and natural conditions.