Cell Membrane (Plasma Membrane)


The cell membrane surrounds the outside of the cell. It is found in both prokaryotic (bacteria) and eukaryotic (plants/animals) cells.

The image below represents the cell membrane in an animal cell.
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Location in a Plant Cell

Notice that the cell membrane (plasma membrane) is surrounded by the cell wall.
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Functions of the Cell Membrane

1. Controls what enters and leaves the cell, thus making is selectively permeable.
2. Protects the inside of the cell.
3. Supports the cell.

Analogy of the Cell Membrane

The cell membrane acts like a door because it regulates what comes in and out of the cell.

Composition of the Cell Membrane

The cell membrane is made of up phospholipid. A phospholipid consists of a polar hear (hydrophilic) and 2 nonpolar tails (hydrophobic). The phospholipids forms a double layer that surrounds the cell (as shown above.) creating a lipid bilayer. The nonpolar tails face each other while the polar heads are located on the outside.

The cell membrane also consists of proteins embedded intracellular for molecule movement and cell signalling, cholestrol for membrane strength, and carbohydrates for aiding in cell identification.
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Fluid Mosaic Model

Describes the cell membrane arrangement:
*very dynamic (constantly moving/changing)
*lipids and protein can move laterally (side to side)
*acts as a fluid
Cell Membrane Overview and Fluid Mosaic Model www.fluidmechanic.org

For more information about the cell membrane visit the following links: