The plasma membrane is called selectively permeable because it allows some substances to pass through it while preventing others. This selectivity is crucial for maintaining the cell’s internal environment and regulating the movement of materials in and out of the cell.
Here’s why:
Regulation of movement:
The plasma membrane acts as a gatekeeper, controlling which molecules can enter or exit the cell.
Maintaining cell composition:
This selective permeability helps the cell maintain a specific internal environment, essential for its proper functioning.
Specific protein channels and transporters:
The plasma membrane contains specialized proteins that facilitate the passage of certain molecules, while others may be prevented from crossing.
Lipid bilayer barrier:
The lipid bilayer structure of the membrane also plays a role in selectively allowing some molecules to pass through, such as small, nonpolar molecules, while larger or polar molecules may require protein assistance.