Learning objectives – to learn about osmosis and
learn why it is important
Osmosis is the movement of water from an area of high water
concentration to an area of low water concentration across a
partially permeable membrane.
Definition – the above definition may need some explaining. A partially
permeable membrane is like a cell membrane which only allows certain
molecules pass. For example it will let water pass but it may not let other
large molecules like starch or protein pass.
High water concentration is simply an area that has a lot of water molecules
in it, the volume as such does not matter, and it is the concentration. So for
example one container may have 500ml of water but it is 100% water, whereas
the other container may have 600ml of water but there are some starch and
protein molecules in there so the total percentage or concentration of water
is at 80%. Therefore container A has a high concentration of water.
The net movement of water
In the above diagram, the orange molecules are too big to pass through the
partially permeable membrane, however the concentration of water is higher
in the left compartment than the right compartment therefore the water moves.