Cell structure

• Investigating cells with a light Microscope

  1. Magnification= image / actual

  2. place slide on the stage

  3. Select lowest power lense (x4)

  4. Turn the focus so the stage is as close to lens as possible but not touching

  5. Move the adjustment knob (stage moves down) to focus the slide then draw an image of what you see repeat 3/4 times

  6. Change next lens to (x10) then repeat

  7. Eye piece x 10 x 10 100

  8. Start at lowest power so you have widest field of view
• Microscopy techniques


  • Light microscopes
  • Electron microscopes
• Electron microscopes


  Allow higher resolution and magnification, enabling biologists to see cells in better detail and understand sub cellular structures
• Eukaryotic cells


  Cells of animals, plants and fungi
• Prokaryotic cells


  Cells of bacteria
• Eukaryotic cells


  • Have a nucleus
  • Have membrane-bound organelles
• Prokaryotic cells


  • No nucleus
  • Free DNA in cytoplasm
• Features of bacterial (prokaryotic) cells

  • Smaller in size
  • Cell membrane surrounded by cell wall
  • Cytoplasm, ribosomes, no mitochondria/chloroplasts
  • Single DNA molecule in cytoplasm
  • Additional DNA on plasmids
  • Binary fission for cell division
• A group of organisms called archaea are also prokaryotic
• Magnification


  Size of image / Actual size of object
• Magnification examples


  • 1 mm = 1000 metre
  • 1 micrometre = 1000 millimetre = 1 micron
• Structures found in animal and plant cells

  • Cytoplasm - jelly-like material containing dissolved nutrients
  • Organelles
  • Nucleus - contains genetic material including DNA, controls cell activities
  • Mitochondria - contain enzymes for respiration, where most energy is released
  • Ribosomes - where protein synthesis occurs
• Structures found only in plant cells

  • Chloroplasts - contain chlorophyll, absorb light energy for photosynthesis
  • Cell wall - made of cellulose fibres, strengthens and supports the cell
  • Permanent vacuole - filled with cell sap to keep the cell turgid
• Investigating cells with a light microscope

  1. Rotate objective lenses to low power

  2. Focus stage close to objective lens

  3. Place slide on stage, centre specimen

  4. Focus slide towards you

  5. Record low power image

  6. Rotate to high power, refocus