Cell Wall — Structure & Function

Plant Cell Walls

Among eukaryotic cells, plant cells have cell walls while animal cells do not. These walls are made of a polysaccharide (a huge sugar molecule) called cellulose.

Think of the walls of your room. They are straight and hard. The same is true for the walls of plant cells. They are straight and hard. This gives plant cells a rectangular shape with straight sides. The main function of these walls is to provide physical support and protection for plant cells.

By the way, plant cells still have a plasma membrane. It sits right inside the outer wall.

Turgor Pressure

We mentioned above that one of the jobs of the cell wall is to give the plant support and structure. The straight, strong walls give the plant cells tensile strength and allow them to stack on top of each other. This enables plants to grow upwards.

However, we've all seen wilted plants. How can we explain that?

To do this, we need to think about the large central vacuole in plant cells that stores water.

Think of the vacuole like a balloon. When it's full, it takes up a bunch of space inside the cell, pushing on the walls.

But, when the vacuole is empty, it deflates. The cell walls don't have anything pushing on them, so they slump inward. The pressure of the vacuole on the walls of the cell is called turgor pressure.

If many of a plant's cells have empty vacuoles, the whole plant looks wilted. But, when you water a plant, the cells fill up their vacuoles and the plant "comes back to life".

Bacterial Cell Walls

Many bacterial cells have walls too. However, their walls are made mostly from peptidoglycan (a mix of amino acids and sugars).

The function is pretty much the same in plant cells and bacterial cells: to provide structure and support.

What Is the Function of the Cell Wall?

The main function of the cell wall is to stabilize and protect the plant cell. You know, like how a wall stabilizes a house. This is what allows some plants to grow incredibly tall. Some prokaryotes have walls around their cells, but plant cells are the only type of eukaryote to have them.

These walls are located on the very outside of the cell, surrounding the cell membrane. Usually stiff, sometimes flexible, they act as a structural support for the cell and organism. These walls are made from carbohydrate fibers, specifically cellulose fibers (a natural polymer), pectic polysaccharides, hemicellulose, and protein. The strength of cellulose is why we can use wood for building.

The walls also filter large, toxic molecules and prevent the cell from over-expanding and bursting. Without a cell wall, plants would fall over, be poisoned by large molecules, or burst from too much water.

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$\color{#8925AE}{\text{Cell Wall}}$ : Gives plant cells extra stability and structure

$\color{#8925AE}{\text{Chloroplast}}$ : A plant cell organelle that captures energy from light for photosynthesis

(Video) Plant Cell Wall

by Christian Rodriguez

One key difference between plant and animal cells is the cell wall: plants have it, but animals don't. This short video explains the parts and purpose of this structure, including the primary cell wall, secondary cell wall, and middle lamella.