Diffusion and Osmosis

• All particles have kinetic energy and constantly move around
• Diffusion: the spreading out of particles, resulting in a net movement from a region of higher concentration to a lower concentration
• A difference in concentration between two areas is known as the concentration gradient
• Particles move down the concentration gradient, this action is passive
• Higher temp = faster movement

  Bigger conc difference = faster
• Osmosis: a passive process by which molecules of a solvent pass through a selectively permeable membrane from a less concentrated solution into a more concentrated one
• Water potential: the amount of free water molecules with no solvent in
• High WP: dilute

  Low WP: concentrated
• Hypertonic cell: when water goes out of the plant cell into an area with lower WP it becomes plasmolysed (wilted)
• Hypotonic: when water moves into the high WP plant cell making it turgid (it bursts because it’s too full)
• Surface : volume ratio

  Bigger surface area : slower diffusion
• Large organisms need specialised exchange surfaces because they have a large surface area and diffusion alone would not be enough to have sufficient oxygen