Biology Unit 3 - Osmosis

Osmosis

Osmosis is the net movemet of water molecules from an area of high concentration to an area of low concentration across a semi-permeable membrane.

A partially permeable membrane is a membrane with very small holes in it, so that some substances can pass through but not others depending on the size of the molecule. Water molecules can pass through but bigger molecules such as sucrose can't.

Water molecules actually pass both ways through a semi-permeable membrane. This is because water molecules move randomly all the time.

The net movement simply means the overall movement of water molecules.

The water molecules move from a dilute solution (water) to a more concentrated solution (sugar solution).

There are more water molecules on one side than on the other, so…