Top Six Functions of the Cell Wall

A cell wall is a semi-permeable and rigid protective layer that is found next to the cell membrane. It is present in plant cells, bacteria, algae, and fungi. It is important to note that animal cells do not have a plasma membrane. This article emphasizes on the top functions of the cell membrane. 

1. Provide Mechanical Strength 

The cellulose cell wall is made of hard materials such as chitin and other hard components that ensure that it is a sturdy material. It derives its strength from cellulose microfibrils, hence allowing it to exert mechanical strength on the plant. It has a skeletal framework, which is not present in other cell membranes that help it to remain in a rigid and definite shape. 

Cell walls use this definite shape and the hard shells to provide mechanical strength to the plant. Cellulose cell walls are also hardened through lignifications, which is a process of adding lignin to the cell wall hence making it tough while at the same time giving it the structural strength of a woody plant. The strength and rigidity of the whole plant depend on the mechanical strength provided by the cell wall. 

2. Maintaining the Shape of the Cell 

Plant cells, which have cellulose cell walls have a definite shape, which is brought about by the presence of a cell wall. The hard outer shell does not become flaccid when the cell loses water. Mostly, lignin and pectin, which are the major components of the cell wall, maintain a rigid structure that allows the cell to maintain a definite shape. Only the isolated protoplast becomes flaccid after losing water. If plant cells were to lose shape, plants would fall. 

This explains why plant cells have to maintain a definite shape at any given time. It is essential to highlight that animal cells don’t have a distinct shape because they do not have a cell wall. Animal cells become flaccid every time they lose water and bulge after gaining water through osmosis. 

3. Controls Cell Expansion 

For growth to occur in plants, cell expansion is necessary. This happens at earlier stages of plant growth. However, growth and expansion of the cells is a controlled process which takes a more extended period. Cell walls are at the center of the cell growth and expansion. For a young plant, cell walls control turgor pressure from within and prevent any chances of cell bursting. This means that anytime the cells gain water, they will expand, but they will not burst. 

In a mature plant, growth and expansion are not necessary. Lignin is therefore added to the cell wall to prevent any expansion. Lignin makes the cell very hard such that it cannot succumb to the turgor pressure generated from within the cell. Maximum growth has been realized, which explains why growth is not needed. 

4. Controls Intracellular Transport 

Transport of important chemical materials has to take place between cells. However, the transfer of materials from one cell to the other is controlled by the cell wall. Very many substances are transported between the adjacent cells, and all have to pass through the cellulose cell wall. The cell wall allows the movement of the very small ions, molecules, and small protein. However, if the materials under transport are very big or are harmful, the cell wall forms a sieve, which prevents these materials from entering through the cell membrane. 

5. Acts as a Reservoir of Food 

Seeds contain a substantial amount of food that will support the seed during the germination process up to the time when it will start performing photosynthesis. In most cases, most of the food and other nutritional requirements are stored on the cell wall. Other foods form a significant proportion of the cell wall. This explains why the cell wall disappears several weeks after the seed germinates. 

6. Protection 

Protection is one of the primary functions of the cell wall and underlines its importance in plant cells. Fungi, bacteria, virus, and other pathogenic microorganisms will always try to attack the cells for food and other benefits. The cell wall triggers the necessary mechanisms to make sure that these organisms don’t get a chance to attack the cell membrane. Cellulose cell walls are known to have both passive and active defense mechanisms that prevent an attack against plant cells.