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What Does the Cell Membrane Do in a Plant Cell?

What Does the Cell Membrane Do in a Plant Cell?
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  • 0:01 Cell Membrane
  • 0:38 Functions
  • 1:08 Structural Function
  • 2:00 Regulation
  • 3:28 Lesson Summary
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Lesson Transcript
Instructor: Dominic Corsini
Plant cells are surrounded by a cell membrane and a cell wall. But why have a membrane if you have a wall? This lesson addresses that question through an investigation into plant cell membrane function.

Cell Membrane

As you may know, all living things are made from cells. How do these cells control what gets into them? Or out of them? Fortunately, each of these cells - be they plant, animal, fungus, or bacteria - contain a cell membrane. The cell membrane is the semi-permeable covering that surrounds all cells. To say something is semi-permeable means that it allows certain substances to pass through them, while prohibiting the passage of others. This is how the cells of maple trees secrete the sugars we use for making maple syrup.

Functions

What do plant cell membranes actually do? Why do they matter? Well, earlier we said that cell membranes are semi-permeable and that they surround the cell. Cell membranes are built of a phospholipid bi-layer that is embedded with various proteins. Phospholipids are essentially fats. This structure lends itself to two primary membrane functions: structure and passage.

Structural Function

First, in conjunction with the cell wall, the plant cell membrane forms the outside boundary of the cell. While the wall provides structural support, the membrane acts as an inner lining capable of holding cytoplasm inside. Cytoplasm is the gel-like fluid that fills the cell. In addition, the plant cell membrane is somewhat flexible. This is important because it allows the cell to expand and contract under different environmental conditions. For example, under low water conditions plants wilt, but still survive. This is because the cell membrane can flex inward and essentially shrivel up to some extent. This characteristic allows the plant cell to survive in less than optimal environmental situations.

Regulation

The second function of the plant cell membrane is to control entry into and exit from the cell. Plant cells can move water across their membranes through a process called osmosis. Cells also regulate the entrance or release of sugars, hormones, waste products, and other molecules - such as proteins - through their membranes.

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