The Biological Function of Cellulose

Lesson Transcript
Instructor: Ryan Hultzman
In this lesson, we will study the importance of cellulose in the biological world. Cellulose is an indispensable part of a plant cell wall and an excellent source of food and energy for microbes and fibers for us!

Definition and Structure of Cellulose

Did you know there is something you eat every day that you can't even digest? It's true! Cellulose is one such food. Let's find out why and how cellulose becomes an essential constituent of our diet, even though we can't break it down in our digestive system.

Cellulose is a tough, water insoluble and fibrous polysaccharide ('poly-' means many and '-saccharide' means sugar). Cellulose is made up of thousands of glucose molecules attached together to form a chain. Think of a beaded necklace with each bead representing a glucose molecule. Several such chains lie side by side to form straight and stable fibers of great tensile strength.

The tensile strength of the cellulose makes it a very useful organic molecule. Cellulose is found in all plants and plant products. Each stem, leaf, root, flower, and fruit contains cellulose, and it is the most abundant organic compound in the world. Let's study some important biological functions of cellulose.

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  • 2:59 Cellulose as a Dietary Fiber
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The Role of Cellulose in Plants

It is the structure of cellulose that makes it so useful. Cellulose is a structural polysaccharide and makes up about 30% of the plant cell wall, which serves many functions including:

  • connecting cells to form tissues
  • signaling cells to grow and divide
  • controlling the shape of plant cells
  • allowing cells to withstand the turgor pressure of the fluids inside them

Think of a cell as a balloon filled with water, the balloon has to withstand the pressure of water inside it. In plant cells, this pressure is known as turgor pressure. The tensile strength of the cellulose fibers in the cell wall provides it with the rigidity and strength needed to tolerate the turgor pressure. Thus, cellulose plays an important role in maintaining the shape of the plant cell and plant organs.

How Cellulose Benefits Microbes

Cellulose is a source of energy for several types of microbes. Large amounts of cellulose is degraded to glucose by both bacterial and fungal microbes. The glucose derived from cellulose degradation is then used by other microbes as a carbon source to produce energy. Many fungi, specifically the members of Basidiomycetes perform critical ecological function by degrading cellulose present in decaying wood.

Some animals can digest cellulose. When an herbivore, say a cow, consumes a plant, like grass, bacteria in their intestinal tract are able to break down the cellulose into smaller parts that the cow's own digestive system can absorb.

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