diffusion

• Diffusion is the movement of particles from an area of high concentration to low concentration.
• The rate of diffusion depends on temperature, surface area, and concentration gradient.
• Osmosis is the diffusion of water across a semi-permeable membrane.
• Diffusion - the net movement of particles in a solution or a gas from an area of high concentration to a lower concentration 
• Equilibrium - a balance, the same number of particles on either side
• Concentration Gradient - the difference between the concentrations of two solutions
• Temperature - affects the speed at which particles can move around
• Surface Area - how much space there is for particles to move through
• Semi Permeable Membrane - allows some substances through but not others
• net movement - the overall, total movement of particles
• larger surface area:volume speed up diffusion
• lungs have short diffusion distance - 1 cell thick wall
• lungs have steep concentration gradient - achieved by ventilation and circulation
• lungs have large surface area - lots of alveoli and in spherical shape
• lungs are moist - help gas dissolve
• lung have rich blood supply - help to maintain concentration gradient
• gills made up with filaments
• gills have steep concentration gradient (well ventilated) - oxygenated water constantly forced over gills
• blood flows through capillaries that surround the gill lamellae
• gills are moist - helps gas dissolve
• gills have rich blood supply - help to maintain concentration gradient
• trachea has no valves so air can flow both ways
• gills have short diffusion distance
• lungs have alveoli which increase surface area
• lungs have large surface area
• alveoli have thin walls
• alveoli have thin walls (1 cell thick)
• gills have large surface area
• digestive system - substance diffuse from the lumen into the villi
• villi has good blood supply
• plants have large surface area - many leaves, lots of cell menbrane in contact with air space, extended root hair cells
• plants have short diffusion distance - leaves are thin and flat
• water diffuse into the root hair cell then to the xylem, then to the palisade layer
• carbon dioxide enter from stomata, and diffuse into palisade layer