by Michael Gotama

Created on: June 17, 2009   Last Updated: July 19, 2009

Osmosis can't be explained separate from membrane cell because osmosis is the diffusion of water across membrane. Although osmosis is kind of diffusion but there are a big differences between diffusion and osmosis. For a short diffusion is particle moving across the membrane from high concentration gradient to low concentration gradient, so it doesn't need energy to do diffusion transport and diffusion called passive transport. Osmosis can be separated from diffusion because the one and only one substance that being transport through osmosis are water and the moving of water from low concentration gradient to high concentration gradient.

Before the relationship between osmosis transport and membrane can be understand, there are some critical point that need to know:

1. Membrane cell consist of phospholipids and glycoproteins. Phosphates construct the head of membrane because it has hydrophilic trait and lipid become the tail of membrane because it has hydrophobic trait.

2. Diffusion is particle moving across the membrane from high concentration gradient to low concentration gradient, but if the concentration on the outside and inside membrane are same the exchange of particle still happen because there is no net exchange between particles, so the transfer of particle doesn't need energy. There are so many examples of diffusion in our life, for example the exchange of gas oxygen and carbon dioxide in lung use a principle of diffusion because oxygen and carbon dioxide are non-polar particle.

3. Isotonic solution is the solution where the concentration of solution same as the concentration of fluid in living thing cell (i.e. red blood cell).

4. Hypotonic solution is the solution where the concentration of solution below the concentration inside of cell.

5. Hypertonic solution is the solution where the concentration of solution higher than concentration inside of cell.

Osmosis can happen in membrane because membrane is selective permeable that means not every particle can pass the membrane, but if there are some particle that membrane want to take it can be easily transferred into a membrane. Non-polar and hydrophobic material can be easily transferred into membrane because phospholipid tails as describe above are hydrophobic, this transfer called diffusion. Water are something that cell need to survive, so in this case membrane use it's selective permeable trait to take water from hypotonic solution until it reach equal concentration of solute (molecules/millimeter). If the solution is hypertonic solutions, the water inside membrane will go out to solution until it reach equal concentration of solute. There is system that regulate water balance in the living things cell, this process called osmoregulation, so the living thing can adapt to their environment which hypertonic or hypotonic.

Reference:

Campbell et al.2008.Biology Concepts & Connection Sixth Edition. United States

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