Specialized Cells

Anexos:

• Cell Structure and Organization

1. Red Blood Cell
   1. Small and numerous in number, which increases surface area for absorption of oxygen.
   2. Has a biconcave shape which increases surface area.
   3. Has a flexible cell membrane so it can squeeze through narrow blood capillaries
   4. Contains a red pigment called haemoglobin which absorbs oxygen to form oxyhaemoglobin.
   5. Absense of nucleus provides more space for haemoglobin.
2. Xylem
   1. Long narrow tubes stretching from the roots, through the stem, to the leaves so the water and mineral ions can be transported from the roots to the leaves.
   2. Arranged end to end with no cross walls to form a hollow continuous tube so that there is no restriction for the flow of water and mineral ions within the xylem vessel.
   3. Walls of the vessel are strengthened by a chemical called lignin.
   4. As lignin builds up, it kills the cytoplasm. There is therefore no layer of cytoplasm to restrict the flow of water and dissolved salts.
   5. Help resist the bending strains caused by the wind.
3. Root hair cell
   1. Has long tubular extension called root hairs which increase surface area for absorption of water and mineral ions.
   2. Root hair is able to form very close contact with the water film in the soil so that water and mineral ions can be absorbed continuously.
   3. Cytoplasm of root hair cells have many mitochondria which releases energy for the active uptake of mineral ions by active transport.