Cell Structure

• The function of magnification adjustors is to focus on the image
• Why red blood cells burst if put into a beaker but not plant cells

  Water enters the cell by osmosis. A plant cell has a cell wall which prevents it from bursting
• Laboratory equipment to prepare cells

  • dye
  • (mounted) needle
  • pipette
  • scalpel
  • forceps / tweezers
• Aseptic techniques

  • Sterilise equipment / surfaces before use
  • Use sterilised agar
  • Secure lid of the Petri dish with (adhesive) tape
  • Only lift lid of Petri dish a little (when setting up plate) or lift lid of Petri dish at an angle (when setting up plate)
• Differences between Xylem and Phloem

  • Structurally: Xylem is made of dead cells and phloem is made of living cells
  • Phloem cells have pores in their end walls and xylem cells do not have pores in their end walls
  • Xylem is hollow or xylem does not contain cytoplasm and phloem contains cytoplasm
  • Xylem contains lignin and phloem does not contain lignin
  • Both made of cells
  • Both tubular
• Adaptations of a root hair cell

  • Thin walls
  • Lots of mitochondria
  • Large surface area
• Functional differences between Xylem and Phloem

  • Xylem transports water / mineral ions and phloem transports (dissolved) sugars
  • Xylem is involved in transpiration and phloem is involved in translocation
  • Xylem transports unidirectionally and phloem transports bidirectionally
  • Both transport liquids / substances throughout the stem / leaves / roots / plant
• Reason why water loss is less at night

  Stomata are (almost completely) closed because it’s cooler / colder or because there’s less / no light
• Reasons why a microscope might not work

  • No cells in the field of view
  • Slide not in the correct position
  • Mirror not in correct position
  • Objective lens not clicked into place or objective lens dirty
  • Student is looking at a (large) air bubble
  • Microscope is not focused
• Using a Petri Dish:

  Pre-inoculation:

  Petri dish and agar sterilised before use to kill unwanted bacteria

  • inoculating loop passed through flame / sterile swab to sterilise / kill (other) bacteria

  
  

  Inoculation

  • loop/swab used to spread/streak bacterium onto agar

  • lid of Petri dish opened as little as possible to prevent microbes from air entering

  
  

  Post-inoculation

  • sealed with tape to prevent microbes from air entering

  • incubate