087-a OSMOSE



A semi-permeable membrane allows only water to pass and not the particles dissolved in it. The liquid on the left of the membrane contains fewer per volume unit than the liquid on the right of the membrane.

The result is a movement of water through the membrane from the left to the right. This process stops at the point that the number of particles per volume unit is equal.



Is the phenomenon that a liquid flows through a semi-pemeable membrane. This membrane allows the liquid to pass but stops the particles dissolved in it when the concentrations of salts are different on both sides. The relation between these two solutions is expressed as osmotic pressure.


Is a process based on diffusion in which a liquid with substances dissolved in it flows through a semipermeable membrane which allows the liquid to pass but stops the substance dissolved in it. The liquid flows to the side with the highest concentration.


The flow of a subtance with a high concentration of that substance to a place with a low concentration.


Substances dissolved in a liquid will passivlely migrate through a membrane when the transport channels are open by their concentration gradient up to the moment when an equilibrium of concentrations is reached.

Osmotic value

Number of particles dissolved per volume unit
The body is one big barrel in which osmotic processes constantly take place on a large scale.

Blood has a certain osmotic value compared to the body cells.

Sports drinks


Schematic survey of the osmotic value of various sports drinks compared to the body.

HYPOTONIC: direction of fluid flow to the body.
HYPERTONIC: direction of fluid flow to the drink.
ISOTONIC: no displacement of fluids by osmosis.

The stomach which is the First place where the sports drink lands is considerd a location outside the body. The osmolarity of the sports drink compared to the body is decisive for the speed in which the fluid passes the wall and is taken up by the body. A hypertonic drink First extracts fluid from the body to dilute the hypertonic drink. In this situation the body loses fluid and dehydration even increases despite the hypertonic fluid intake. Because of the fact that more fluid goes to the stomach one can feel a full and sloshing sensation causing nausea and vomiting.