Thin, flexible barrier that surrounds all cells; regulates what enters and leaves the cell (aka: phospholipid bilayer)
Cell membrane
The thin, flexible barrier that surrounds all cells is called the cell membrane or plasma membrane. The cell membrane is a selectively permeable layer that regulates the movement of substances in and out of the cell. It is made up of a phospholipid bilayer, which is a double layer of phospholipid molecules with hydrophilic (water-loving) heads and hydrophobic (water-repelling) tails.
The phospholipid bilayer creates a barrier that prevents most substances from freely crossing it. However, some substances such as small, nonpolar molecules (like oxygen and carbon dioxide) can passively diffuse through the membrane. For other substances such as ions and larger molecules, specialized membrane proteins, such as channels, transporters, or pumps are required.
Overall, the cell membrane is an essential component of the cell that plays a vital role in maintaining the cell’s integrity and regulating the movement of substances in and out of the cell.
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