L.O 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, 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.

This diagram will help to explain

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.


Uses for osmosis

Osmosis is used in the body, it is used as a means of transporting liquid in and out of cells. The main liquid substance in the body is tissue fluid, which is usually transported in the blood and transferred across to cells

If a cell is short of water then the cell will begin to shrink, therefore water will move into the cell

If the cell has to much water, it will expand, therefore eater will move out of the cell




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