Why is the cell membrane described as semi-permeable? Oct 20, Related questions How is the cell membrane affected by temperature? How does the cell membrane change shape? How does a cell membrane affect water movement? Why are cell membranes selectively permeable? The polar heads point both outward toward the environment of the cell and inward toward the cytosol.
In this way, a hydrophobic region of lipid tails separates the two bodies of solution. While water and other small molecules can slip through the gaps between the phospholipid molecules, other molecules like ions and large nutrients cannot force their way into or out of the cell.
This makes the phospholipid bilayer an excellent semipermeable membrane that allows cells to keep their contents separated from the environment and other cells. The concentration of the solution bound by a semipermeable membrane can be described by its tonicity as compared to the environment or other cells.
Definition noun A membrane that is selectively permeable , i. Supplement An example of such membrane is the cell membrane wherein it allows passage of only certain types of molecule s by diffusion and occasionally by facilitated diffusion.
See also: cell membrane. It only takes one biological cell to create an organism. A single cell is able to keep itself functional through its 'miniature machines' known as organelles.
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