Definition

Noun: A semipermeable membrane is a thin, flexible layer or barrier that allows certain molecules or ions to pass through it by diffusion, while blocking others. It is selectively permeable, meaning it permits the passage of some substances but not all.

Examples

• The cell's outer layer is a semipermeable membrane that controls what enters and exits.
• In a science experiment, water moved through the semipermeable membrane from the dilute solution into the concentrated one.
• Reverse osmosis uses pressure to force water through a semipermeable membrane, leaving contaminants behind.

Advanced Usage

• Osmosis: This is a key process involving a semipermeable membrane, where solvent molecules (like water) move from an area of lower solute concentration to an area of higher solute concentration to equalize concentrations on both sides.
• Dialysis: A medical or laboratory process that uses a semipermeable membrane to separate small molecules (like waste products in blood) from larger ones (like proteins).

Variants and Related Words

• Selectively permeable membrane: A synonym often used interchangeably with semipermeable membrane.
• Permeable (adj): Allowing liquids or gases to pass through.
• Impermeable (adj): Not allowing fluid to pass through.
• Membrane (n): A thin, pliable sheet or layer acting as a barrier or lining.

Synonyms

• Selectively permeable membrane
• Partially permeable membrane
• Differential membrane

Related Phrases and Concepts

• Transport across a membrane: The general movement of substances through a membrane, which can be passive (like diffusion) or active (requiring energy).
• Concentration gradient: The difference in concentration of a substance across a space, which drives diffusion through a semipermeable membrane.

Noun

1. a membrane (as a cell membrane) that allows some molecules to pass through but not others