IBDP Biology: Plant Cell Structure

In this topic of IBDP Biology, we will learn about Plant Cell Structure.

• When it comes to IBDP Biology, plant cells are eukaryotic.
  • As are animals, fungi and protoctists.
• They contain a nucleus and other membrane bound organelles:
  • Mitochondria, ER, generally one Golgi.
• However, there are fundamental differences between plant cells and animal cells.

• Cell wall
  • Thick layer outside the cell membrane to give strength and rigidity.
  • Major component is cellulose.
  • When it comes to IBDP Biology, cell wall allows movement of water through and along it.
  • Have channels called plasmodesmata which connect the cytoplasms of adjacent cells.
  • Primary cell wall – made of cellulose;
  • Secondary cell wall – produced in some plant cells when fully developed, eg xylem.
    • Contains cellulose and can contain lignin which makes it impermeable

• Chloroplast
  • Site of photosynthesis, only found in plants and algae.
  • 5 to 10 micrometers long.
  • Double membrane – chloroplast envelope.
  • Thylakoids
    • Membranous discs
    • Photosynthetic pigments are embedded in the membrane.
    • Stacked into grana 
    • These are linked by intergranal lamellae.
  • Fluid filled matrix is called stroma.
    • This also contains starch grains, ribosomes, and circular DNA.

• Vacuoles
  • Membrane–bound sacs = tonoplast
  • Contain cell sap:
    • Sugars, amino acids, pigments, mineral salts.
    • Aqueous solution
  • Stores food.
  • Help keep cell rigid and turgid.

• When it comes to IBDP Biology, plant cells have numerous adaptations, eg:
  • Photosynthesis - palisade cells.
    • Long thin and cylindrical, tightly packed:
      • Forms a continuous layer that absorbs sunlight.
    • Numerous chloroplasts:
      • Capable of moving towards the side where light is entering.
    • Large vacuole:
      • Mantains turgor.
      • Pushes chloroplasts towards edges of cell.

• Transport
  • Xylem:
    • Dead cells forming vessels.
    • Allows for transport of water and dissolved nutrients up the plant.
    • Extra thickening with lignin.
    • No cytoplasm.

• Water uptake – root hair cells:
  • Form the piliferous laer around the root.
  • Long cytoplasmic processes called root hairs.
  • Increase the surface area for water transport.

This is the end of this topic

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