Osmosis (Cambridge (CIE) IGCSE Combined Science): Revision Note

All cells are surrounded by a cell membrane which is partially permeable

Water can move in and out of cells by osmosis

Osmosis is the diffusion of water molecules from a dilute solution (low solute concentration) to a more concentrated solution (high solute concentration ) across a partially permeable membrane

In doing this, water is moving down the concentration gradient from where there is more water to where there is less

The cell membrane is partially permeable which means it allows small molecules (like water) through but not larger molecules (like solute molecules)

Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane

To understand this topic with clarity, it is important to understand the following

• High water potential = dilute solution = low solute concentration (right side of diagram)

• Low water potential = concentrated solution = high solute concentration (Left side of diagram)