Exchange of materials

- Osmosis is the diffusion of water

- Across a partially permeable membrane

- NET movement of particles, high to low concentration

- Only water molecules

- Allows against concentration gradient

-Requires the use of energy released in respiration

-Ions, from dilute solutions can be absorbed

- i.e. Mineral ions by root hair cells

-Glucose reabsorbed by the kidney

- Sweating causes dehydaration

- Need to replace sugar, mineral ions and water lost

- The water helps to rehydrate

- Help to balance concentration of fluids

- If concentration matches the body fluids the solution is isotonic

- Large surface area, Thin walls, Short diffusion path

- Gaseous exchange surface- Alveoli

- Good blood supply

- Ventilated maintain concentration gradient

- Oxgen diffuses into the cappilaries

- CO2 diffuses back out

Breathe in:

- Intercostal muscles contract

- Ribs up and out

- Volume of thorax increases- Pressure decreases

- Air drawn out

Breath out:

- Opposite of above

'Iron lung'- Vacuum formed in cylinder creates a negative pressure, air pumped in air forced out

Positive pressure- Force measured ammounts of air into lungs

                           - Down the Trachea

Positive pressure aids often smaller

- Thin diffusin path

- Large surface area- finger like projections

- Good blood supply

- Moist

- Soluble products of digestion

Stomata- allows carbon dioxide to diffuse into the leaf

Leaves- Flat and thin, internal space- increase surface area

Root hair cells- Surface area- absorb water and minerals

- Water lost from leaves, in evaporation

- Water vapour lost through the stomata, when open to allow carbon dioxide to entre

- The guard cells close to prevent water loss

- Wilting- reduces surface area and reduces water loss