B3 (Biology)

Life Processes 2

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  • Created by: Stephen
  • Created on: 16-12-09 19:47

Gas and Solute Exchange.

  • they need the substances to be GASES or DISSOLVED
  • waste substances need to move out of the cells through diffusion, osmosis and active transport
  • diffusion is where particles move from a HIGHER CONCENTRATION to a LOWER CONCENTRATION
  • osmosis is the same as diffusion however refers to the movement of WATER PARTICLES across a PARTIALLY PERMEABLE MEMBRANE
  • the surfaces in which diffusion and omsosis take place are optimized for the processes to maximise effectiveness.
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Gas and Solute Exchange In the Leaf

  • the STRUCTURE of leaves lets gases DIFFUSE in and out of cells
  • carbon dioxide diffuses into the air spaces within the leaf, and then into the cells (for photosynthesis)
  • underneath part of a leaf is an exchange surface
  • its covered with small holes (stomata) which the carbon dioxide diffuses in through
  • both water vapour and carbon dioxide diffuse through the stomata
  • the size of the stomata are controlled by the guard cells
  • they close if the plant is losing water too fast
  • the flattened shape of the leaf is to increase its surface area so exchange of substances is more efficient
  • TRANSPIRATION : is the process in which water vapour escapes by diffusion (higher to lower concentration)
  • TRANSPIRATION happens faster when the air around the leaf is dry and in windy conditions
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Diffusion in the Lungs and Digestive System

  • the lungs transfer oxygen to the blood and remove waste carbon dioxide from the blood
  • to do this the lungs contain millions of air sacs (alveoli) where the gas exchange takes place
  • the alveoli are specialised to optimize the diffuson of oxygen and carbon dioxide : they have a large surface area, moist lining for dissolving gases, very thin walls and a copius blood supply
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There is lots of detail on these cards, so well done! :)



Great, really helpful =)



Awesome! =D

Just the right vocabulary used! Very helpful! Thanks!

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