Cell Transport

Diffusion Migration of substances from regions where their concentration is high to regions where their concentration is low. Diffusion is important in many life processes. It occurs, for example, across the alveolar membrane of the lung, which separates the carbon-dioxide-rich blood from the oxygen-rich air. Oxygen diffuses across the membrane and becomes dissolved in the blood; carbon dioxide diffuses across the membrane into the air.

Concentration gradient – a difference between concentrations in a space.

Osmosis Diffusion of fluid through a semipermeable membrane from a solution with a low solute concentration to a solution with a higher solute concentration until there is an equal concentration of fluid on both sides of the membrane.

Animation of water molecules moving across a selectively permeable membrane. Water molecules are the small blue shapes The solute is the green. The solute is more concentrated on the right side to start with, which causes molecules to move across the membrane toward the left until equilibrium is reached. LEFT RIGHT com/bio1/diffusion.html#