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All cells have a cell membrane on the outside of them that acts like a skin. Plant cells go one step further and have a cell wall – a protective outside that provides support and other functions.

What is a Cell Wall?

All living things are composed of cells. They are the building blocks of all life. Cells come in many different shapes and have different functions. Plant and animal cells are different, too.

The main difference between plant and animal cells is that plant cells have a cell wall on the outer layer, whereas animal cells only have a cell membrane. The cell wall is a protective layer outside the cell membrane that also provides support for the cell’s structure.

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Function of a Cell Wall

The cell wall gives the plant its actual shape. It acts as a gatekeeper, because it determines what can come in and out of the cell in order to keep the cell protected. It is kind of like the outside bricks of a castle, only, as you will learn as you read on, there are holes throughout this castle. Those holes do make the cell vulnerable, but they are important to the function of the cell.

A plant cell has a cell wall, whereas an animal cell only has a cell membrane.

Plant Cell

A redwood tree and a dandelion both have cell walls on the outside of all of their cells. The cell walls are there to give the plants their shape and support; however, the cell walls act and are constructed a little different to meet the needs of the particular plant. For instance, a 100-foot redwood tree needs a very strong and rigid plant cell wall so that it can grow to its great height and not fall over in the wind. On the other hand, a little yellow dandelion out in the field needs to have more plasticity so that it can bend, not break, as the wind blows through the field.

A dandelion needs to have plasticity to be able to bend in the wind.
Cell walls are composed of three layers.
Cell Wall Layers

The top layer is the strangely-named middle lamella. This outer layer is shared by neighboring cells, and it connects the cells together to form a strong structure. It is also very flexible. The middle lamella is rich in pectins, which help to strengthen the plant and give it the ability to resist compression.

They also contain enzymes that help to breakdown the cell wall, allowing the plant to change its structure. This process is important when fruit is ripening.The primary wall is the next layer. It is composed of cellulose in the form of microfibrils. These cellulose microfibrils weave together with glycans, increasing the strength of the cellulose. Pectins can also be found in the primary cell wall.

With all of this strength, you would think nothing could squish a dandelion.The third and final layer is the secondary wall. This layer is extremely rigid and provides compression strength. It helps stop the plant from getting squished. The secondary wall has a very similar composition as the primary wall, only it has more stuff in it – it contains lignin, which is very hard and has considerable strength. The secondary wall also protects the plant from invading bacteria or fungi.

Lesson Summary

A plant cell wall is constructed around the outside of the cell to give plants a strong and protective outer layer.

The cell wall can be divided into three layers, each of which is made for strength and protection. These layers and their compositions not only protect the cell but allow for the cell to function. The three layers are the middle lamella, the primary wall and the secondary wall. There are passageways for nutrients to enter and waste to leave. The plant cell wall is unique to plants and plays many vital roles to making plants what they are.

Learning Outcomes

After you are done with this lesson, you should be able to:

  • Describe the cell wall and recall its purpose
  • Explain how a plant’s cell wall provides support and protection
  • List some of the functions of a plant’s cell wall
  • Discuss the components of a plant’s cell wall
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