B1

• “Preparing biological samples foe examination”

  Animal cells - cheek cells

  1. put a small water drop on the microscope slide
  2. swab your cheeks with a cotton bud
  3. rub the cotton bud in the drop of water
• “Preparing biological samples for examination”

  Plant cells - Onion 🧅 epidermal cells

  1. put a water drop on the microscope slide
  2. peel some onion skin
  3. use forceps to put on water drop - make sure skin is flat + no air bubbles.
  4. Stain with iodine
• “Preparing biological samples for examination”

  Other biological structures - human hair or animal fur

  1. put drop of glycerol on microscope slide
  2. cut small piece of hair / fur
  3. use forceps to put it on the glycerol
  4. place thin glass square (coverslip) over it
  5. put a drop of stain next to coverslip
  6. draw the stain by putting filter paper next to it.
• Risks (compound microscope practicals)

  1. looking down the microscope - “illumination too bright”
  2. care when using stains
  3. care when handling glass (coverslip) , microscope slide and mounted needles
• “Investigating cells with a light microscope”

  1. Rotate the objective lenses to the lowest power (x10)
  2. Turn the coarse focus to move the stage as high to the objective Lenze as possible
  3. Place the slide on the stage.
  4. Focus the slide by turning coarse focus adjustment
  5. Draw what you see
  6. rotate lenses so the highest power one is lined with stage
  7. Use fine focus adjustment to re-focus the slide.
• What is the maximum magnification for a light microscope?

  x 1,500
• Resolution

  The fineness of detail that can be seen.

  The higher the resolution, the more detail
• The electron microscope

  • use a beam of electrons - instead of light rays
  • Bigger, heavier, and more expensive
  • Maximum magnification of x 1,000,000
• Why might we use iodine solution when looking at onion cells underneath a microscope?

  • it binds to starch in plant cells
  • it is a stain, so it makes cellular structures easir to see