eukaryotic cell structure (plants)

• the cell wall - Middle Lamella

  A layer made of pectin which holds cell walls of different plant cells together, like a glue

  A layer of pectin (which combines with calcium to make calcium pectate) forms this middle layer

  Cellulose microfibrils form a matrix around this to form the cell wall
• the cell wall -

  • Primary cell walls are flexible but secondary cell walls thicken over time making the cells more rigid.
  • In some plants this secondary thickening can lead to the formation of wood as lignin is added to the cellulose.
• the plasmodesmata -

  Small gaps or channels between cells allowing communication

  • They are threads of cytoplasm lined with cell membrane that connect the cells to each other, passing signalling substances between them.
  • The interconnected cytoplasm is called symplast.
• permanent vacuoles -

  Fluid filled spaces with specialised membrane called a tonoplast

  This controls the water potential of the cell and also are important in cell shape
• chloroplast - Structure:

  • 2 membranes separated by fluid filled space
  • Inner membrane is continuous with a network of thylakoids
  • A stack of thylakoids is called a granum
  • Chlorophyll molecules are present on these membranes.
• chloroplast - Function:

  • Site of photosynthesis
  • Light energy is used to derive carbohydrate molecules from carbon dioxide.
• amyloplasts -

    These are like chloroplasts however they are colourless and store starch