Gas and Solute Exchange
Exchange surfaces are ADAPTED to maximise effectiveness.
Carbon dioxide diffuses into the air spaces within a leaf (stomata), then it diffuses into cells where photosynthesis happens.
Water vapour and oxygen diffuse out through the stomata.
The size of the stomata are controlled by guard cells.
Diffusion = particles move from an area of high concentration to an area of low concentration
Osmosis = similar to Diffusion, but only in water. The water moves across a partially permeabl membrane.
Active transport = goes against the concentration gradient. Eg. from an area of low concentration to an area of high concentration.