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semipermeable membrane
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Three-panel diagram showing the diffusion of chloride and potassium ions across a semipermeable membrane. Panel A illustrates movement driven by a concentration gradient, panel B shows both concentration gradient and opposing electrostatic force, and panel C depicts equilibrium potential where forces balance and ion flow is stable. Chloride ions are marked in blue, potassium ions in red, with direction arrows indicating ion movement. Two U-shaped tubes illustrate water diffusion across a semipermeable membrane. In diagram A, water moves from side 1 to side 2, driven by osmotic pressure and a concentration gradient, with impermeant substances unable to cross the membrane. In diagram B, hydrostatic pressure opposes the movement. Key concepts such as permeability, osmotic pressure, and impermeant membrane are labeled. osmotic pressure
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semipermeable membrane

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Three-panel diagram showing the diffusion of chloride and potassium ions across a semipermeable membrane. Panel A illustrates movement driven by a concentration gradient, panel B shows both concentration gradient and opposing electrostatic force, and panel C depicts equilibrium potential where forces balance and ion flow is stable. Chloride ions are marked in blue, potassium ions in red, with direction arrows indicating ion movement.
Ion movement across a semipermeable membrane Diffusion of ions across a semipermeable membrane. (A) A high concentration of potassium chloride (KCl) is placed on side 1, opposite a semipermeable membrane from a low concentration. The membrane allows only potassium (K+ ) to diffuse, thereby establishing an electrical potential difference across the membrane. (B) The separation of charge creates an electrostatic voltage force, which draws some K+ back to side 1. (C) At equilibrium there is no net flux of K+ in either direction. Side 1, with the higher concentration of KCl, has a negative charge compared with side 2.

A semipermeable membrane is a barrier that allows certain molecules or ions to pass through by diffusion, but blocks others. This selective permeability is crucial for many biological and industrial processes.

In biological contexts, the cell membrane acts as a semipermeable membrane. It separates the cell's internal environment from the external surroundings, controlling the passage of essential nutrients into the cell and waste products out. This process is vital for maintaining cellular homeostasis.

A key phenomenon involving semipermeable membranes is osmosis, the movement of water across the membrane from an area of lower solute concentration to an area of higher solute concentration. This process is fundamental to water uptake in plants and fluid balance in animal cells.

Industrially, semipermeable membranes are utilized in technologies like reverse osmosis for water purification and desalination, where they separate solutes from solvents under pressure.12345

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
5 Britannica Sources
  1. cell - Permeation
  2. osmosis
  3. semipermeable
  4. osmotic pressure
  5. Fast Facts about the Cell Membrane

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