Question Video: Recalling the Role of Cellulose in Providing Shape and Support to a Plant Cell | Nagwa Question Video: Recalling the Role of Cellulose in Providing Shape and Support to a Plant Cell | Nagwa

Question Video: Recalling the Role of Cellulose in Providing Shape and Support to a Plant Cell Biology • Third Year of Secondary School

Plant cells can take in large amounts of water and swell up. What component of the plant cell wall allows this change in shape to occur without letting the cell burst?

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Video Transcript

Plant cells can take in large amounts of water and swell up. What component of the plant cell wall allows this change in shape to occur without letting the cell burst? (A) Chitin, (B) collagen, (C) cellulose, or (D) fibrin.

The question is asking us about a substance that can be deposited into plant cell walls that allows them to swell with water but not burst. To work out what this substance is, let’s first take a look at some of the structures we would be likely to find in a typical plant cell like this one. Within each plant cell is a structure called a vacuole. The large permanent vacuoles in plant cells are filled with a substance called cell sap. Cell sap contains a lot of water molecules, which we’ll represent in our diagram as blue dots. And it also contains dissolved solutes and certain enzymes.

When the vacuole is especially filled with water, it exerts a high turgor pressure upon the cell membrane that surrounds the plant cell. As plant cells also contain a rigid cell wall surrounding the cell membrane, a high turgor pressure allows these cells to become turgid and swollen rather than bursting. The question mentions that there is a component of plant cell walls that allow them some flexibility, strength, and structure. This is describing a method of structural support in plant cells.

Structural support is the permanent deposition of strong polymers into the cell walls of certain plant cells to maintain the shape of the plant and its cells. There are many different polymers that can be deposited into different plant cell walls, depending on their location and function, such as lignin, pectin, or cutin. But all plant cell walls have one polymer in common, cellulose. Cellulose is a strong insoluble polymer made of chains of thousands of glucose molecules joined together. These chains form a mesh within plant cell walls that act as a supportive barrier. It is also what allows the plant cells to change shape, for example, when the vacuoles are filled with water and are exerting turgor pressure upon the cell wall.

A key difference between plant and animal cells is that animal cells do not have cell walls, though they are surrounded by a cell membrane. If a typical animal cell like this one absorbed a lot of water, unlike the cell wall of a plant cell, the cell membrane cannot withstand the turgor pressure that is exerted upon it by all of these water molecules. This causes the animal cell to burst as it does not have the cellulose cell wall that a plant cell would to help it keep its shape.

Therefore, we’ve worked out that the component of a plant cell wall that allows it to change in shape without bursting is cellulose.

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