Diffusion in specialised

absorb nutrients from digested food molecules into the bloodstream

VILLI : increase surface area allowing more nutrients to be absorbed into the bloodstream and increasing the rate of diffusion MICROVILLI: each villus is lined with microvilli which increase SA further allowing more nutrients to be absorbed into the bloodstream and increasing the rate of diffusion VILLI WALLS ARE ONE CELL THICK: which provides a short diffusion pathway (allows nutrients to be absorbed quickly into the bloodstream) , this increases the rate of diffusion VILLI HAVE A RICH BLOOD SUPPLY: which quickly carries away absorbed nutrients, this maintains a steep concentration gradient and increases the rate of diffusion.

to carry out gas exchange , allowing oxygen to enter the bloodstream and carbon dioxide to leave

ALVEOLI: lungs contain alveoli which provide a large SA for gas exchange to occur , this increases the rate of gas exchange ALVEOLI HAVE A RICH BLOOD SUPPLY: which maintains a steep concentration gradient , increasing the rate of gas exchange ALVEOLI HAVE THIN WALLS: alveoli and capillaries are one cell thick which provides a short diffusion pathway , increasing the rate of gas exchange MOIST LINING: helps gases to dissolve , increasing the rate of gas exchange

to carry out gas exchange under the water

GILL FILAMENTS: fish gills are made from gill filaments which provide a large SA for gas exchange to occur , this increases the rate of gas exchange LAMELLAE: are folds in the membrane which provide a large SA , increasing the rate of gas exchange WALLS OF CAPILLARIES AND MEMBRANE ARE THIN: which are one cell thick and provide a short diffusion distance , this increases the rate of gas exchange COUNTER-CURRENT FLOW SYSTEM: blood and water flow in opposite directions which maintains a steep conc. gradient and increases the rate of gas exchange EXTRA : ( these ..) (ensure as much oxygen diffuses into the blood as possible)

absorb water and mineral ions from soil (note: water used in photosynthesis)

LONG EXTENSION- provide a large SA available for the absorption of water and mineral ions THIN CELL WALLS: outer epidermis is one cell thick , this provides a short diffusion distance , increasing the rate of absorption NO CHLOROPLAST -it would take up unnecessary space as it is underground isn’t exposed to sunlight underground for photosynthesis removed: - SEMI-PERMEABLE CELL MEMBRANE- allows water and mineral ions to pass into the cell EPIDERMIS IS COVERED IN ROOT HAIR CELLS: which provide a large SA for the absorption of water note : epidermis = outer layer WATER IS TRANSPORTED INTO THE XYLEM: which maintains a steep concentration gradient , increasing the rate of diffusion

allow oxygen to diffuse out of the cell and carbon dioxide to diffuse into the cell for photosynthesis (note: to produce food for the plant)

BROAD,FLAT LEAVES: increase SA for gas exchange and absorbing sunlight STOMATA: tiny pores to enable gas exchange SPONGY MESOPHYLL: has many air spaces to allow gases to move easily and maintain a steep conc. gradient THIN LEAF: creates short diffusion pathway ,increasing rate of diffusion