Physiology · General Physiology

Osmosis, osmotic pressure and tonicity

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Definition

  • Osmosis is the movement of solvent from a solution of lower solute concentration to one of higher solute concentration across a semipermeable membrane.
  • A semipermeable membrane allows passage of solvent but not solute.

Mechanism of Osmosis

  • Net water flux runs from the lower-solute-concentration solution to the higher-solute-concentration solution, until osmotic equilibrium is reached.
  • This increases the volume of the higher-concentration compartment.

Osmosis across a semipermeable membrane, before and after equilibrium