Biology Unit 2a - Specialised Cells: Higher

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  • Specialised Cells: Higher
    • Palisade Leaf Cells
      • They are adapted for PHOTOSYNTHESIS.
      • Packed with CHLOROPLASTS for PHOTOSYNTHESIS. More of them are crammed at the top of the cell - so they're nearer the light.
      • TALL shape means a lot of SURFACE AREA exposed down the side for ABSORBING CO2 from the air in the leaf.
      • THIN shape means that you can pack loads of them in at the top of a leaf.
      • Palisade leaf cells are grouped together at the top of the leaf where most of the PHOTOSYNTHESIS happens.
    • Guard Cells
      • They are adapted to OPEN AND CLOSE PORES.
      • Special kidney shape which OPENS and CLOSES the STOMATA (pores) in a leaf.
      • When the plant has LOTS of water the guard cells fill with it and go plump and TURGID. This makes the stomata OPEN so GASES can be exchanged for PHOTOSYNTHESIS.
      • When the plant is SHORT of  water, the guard cells lose water and become FLACCID, making the stomata CLOSE. This helps stop too much water vapour ESCAPING.
      • THIN outer walls and THINKENED inner walls make the opening and closing work.
      • They're also SENSITIVE TO LIGHT and CLOSE AT NIGHT to save water without losing out on photosynthesis..
      • Guard cells are therefore adapted to their function of allowing GAS EXCHANGE and CONTROLLING WATER LOSS within a LEAF.
    • Red Blood Cells
      • CONCAVE shape gives a big SURFACE AREA  for absorbing OXYGEN. It also helps them pass SMOOTHLY through CAPILLARIES to reach body cells.


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