Gas and Solute exchange
- Created by: Jo Wells
- Created on: 07-04-13 11:03
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- Gas and Solute exchange
- substances move by DIFFUSION, OSMOSIS and ACTIVE TRANSPORT
- exchange surfaces are adapted to maximise efficiency
- have a large surface area
- = lots of substances can diffuse at once
- are thin
- = short distance for substances to diffuse
- (in animals) are often ventilated
- = air moves in and out
- (in animals) have lots of blood vessels
- = get substances into and out of the blood quickly
- have a large surface area
- structure of leaves lets gases diffuse in and out of cells
- underneath the leaf is covered in holes called stomata
- which let carbon dioxide diffuse through
- oxygen and water vapour also diffuse out through the stomata
- water vapour is lost from all over the leaf, but mainly via the stomata
- the water vapour evaporates from the cells inside the leaf
- it then escapes via diffusion as there's a lot of it inside the leaf and less outside
- evaporation is fastest in hot, dry and windy conditions
- the water vapour evaporates from the cells inside the leaf
- water vapour is lost from all over the leaf, but mainly via the stomata
- the size of the stomata is controlled by guard cells
- these close the stomata if the plant is losing water faster than it's being replaced by the roots
- without the guard cells the plant would quickly wilt
- the flattened shape of the leaf increases the area of this exchange surface so it's more effective
- the walls of the cells inside the leaf form another exchange surface
- the air spaces inside the leaf increase the area of this surface so there's more chance for CO2 to get into the cells
- underneath the leaf is covered in holes called stomata
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