Movement of molecules in and out of cells
Dissolved substances move by diffusion and by active transport.
Diffusion: movement of particles in a liquid or gas from an area of high concentration to low concentration.
The greater the difference in concentration, the faster the rate of diffusion.
2 examples of diffusion through the cell membrane: Oxygen required for respiration diffuses into cells OR Carbon dioxide produced by respiration diffuses out of cells.
Osmosis: The movement of water from a dilute to more concentrated solution through a partially permeable membrane (that allows the passage of water molecules)
If there is a higher solute concentration on one side of a membrane, water will move in that direction.