Tonicity

Tonicity (Greek τόνος tonos, tension, tension '), also referred to as "effective osmolarity " is a qualitative measure of the osmotic pressure gradient between two solutions with each other through a semi-permeable membrane in contact. Tonicity has no unit.

Cells containing more solutes (especially salt ions) than the surrounding liquid, water penetrates into the cell, thereby increasing the volume and the internal pressure is greater than that in the surrounding area. Tonicity is a relative measure of this difference in pressure.

Use

The term tonicity is frequently used in biological medicine and biochemistry at the description of the behavior of the cell ( the cytoplasm is " Solution I " ), through their cell membrane ( " semipermeable membrane " ) from a surrounding liquid ("Solution II" ) are separated. As the tonicity is described as the difference of the osmotic pressure, it is only caused by solutes which - in an equilibrium - may not pass through the membrane. Solutes can move freely through the membrane do not affect tonicity.

Typical systems for which the term tonicity plays a role and is used are

  • Blood cells in serum;
  • Prokaryotes in the fermentation medium;
  • Eukaryotic animal, plant or fungal cells in a chemically pure composite buffer or a complex composite culture medium;
  • Artificial membrane vesicles (liposomes) - e.g. in reconstitution experiments - in physiological buffers.

Hypertonic / hypertonic

  • A solution has a higher osmotic pressure than a comparison medium.
  • A cell (more precisely, the cytoplasm, the medium within a cell ) having a higher osmotic pressure than the surrounding medium, it (the liquid outside the cell).

In medicine, hypertension means or hypertonic:

  • A solution has a higher osmotic pressure than the human blood.
  • Technical term for high blood pressure
  • Technical term for the tension of the muscles, ie Muscle tone is unphysiological increases.

Isoton / isotonic

The term isotonic ( syn. isotonic, from Greek ἴσος isos, equal to ' and τόνος tonos, tension, tension ') means in biochemistry and biology:

  • A solution has the same osmotic pressure as a comparison medium.
  • A cell (more precisely, the cytoplasm, the medium within a cell ) has the same osmotic pressure as the surrounding medium ( the liquid outside the cell).

In medicine isotonic means:

  • A solution has the same osmotic pressure as human blood.
  • Technical term: The muscle shortens without change in force ( " equal clamped" ).

Hypotonic / hypotonic

The term hypotonic ( syn. hypotonic; ὑπό Greek hypo, ' Tonos and τόνος, suspense, tension ' below ) means in biochemistry and biology:

  • A solution has a lower osmotic pressure than a comparison medium.
  • A cell (more precisely, the cytoplasm, the medium within a cell ) having a lower osmotic pressure than the surrounding medium, it (the liquid outside the cell).

In medicine, hypotension means or hypotonic:

  • A solution has a lower osmotic pressure than the human blood.
  • Technical term for low blood pressure
  • Technical term for the tension of the muscles, ie Muscle tone is unphysiological low.
Serum (blood)
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