specialised cells

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  • specialised cells
    • Palisade leaf cells
      • adapted for photo-synthesis
      • packed with chloroplasts
        • more of them are at the top of the cell so they are nearer the light.
      • tall shape means a lot of the surface area is 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 the leaf.
      • grouped together at the top of the leaf where most of the photo-synthesis happens.
    • Guard cells
      • adapted to open and close pores.
      • special kidney shape which opens and closes the stomata in a leaf
        • adapted to open and close pores.
      • when the plant has lots of water the guard cells fill with it and go plump and turgid.
        • makes the stomata open so gases can be exchanged for photo-synthesis.
      • when the plant is short of water the guard cells lose water and become flaccid, making the stomata close
      • thin outer walls and thickened inner walls making the opening and closing work.
      • sensitive to light and close at night to save water.
        • guard cells are therefore adapted to their function of allowing gas exchange and controlling water loss within a leaf
    • Red blood cells
      • adapted to carry oxygen.
      • concave shape gives them a big surface area for absorbing oxygen
        • helps them pass smoothly through capillaries to reach body cells.
      • packed with haemoglobin - the pigment that absorbs oxygen.
      • no nucleus- leaves even more room for haemoglobin.
    • Sperm and Egg cells
      • functions of an egg cell
        • carry the female DNA
        • to nourish the developing embryo in the early stages.
          • egg cell contains huge food reserves to feed the embryo.
      • when a sperm fuses with the egg, the eggs membrane instantly changes its structure to stop any more sperm getting in.
        • makes sure the offspring ends up with the right amount of DNA.
      • function of a sperm cell
        • get the male DNA to the female DNA.
          • has a long tail and a streamlined head to help it swim to the egg.
          • has a lot of mitochondria in the cell to provide the energy needed.
      • sperm also carried enzymes in their heads to digest through the egg cell membrane.


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