Cells

• Organisms


  • Can be Prokaryotes or Eukaryotes
• Cells


  • Can be either Prokaryotic or Eukaryotic
• Eukaryotic cells


  Include animal and plant cells
• Prokaryotic cells


  Are small and single-celled (e.g. bacteria)
• Eukaryotes


  • Are organisms made up of eukaryotic cells
• Prokaryote


  A single-celled organism
• Parts of a cell

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Animal cells


  • Have nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• Plant cells


  • Have all the parts of animal cells plus cell wall, permanent vacuole, chloroplasts
• Bacterial cells are much smaller than plant and animal cells
• Bacterial cells


  • Don't have chloroplasts or mitochondria
  • Have a single circular strand of DNA in the cytoplasm
  • May contain plasmids
• Prepare a slide to view animal cells

  1. Add a drop of water to the middle of a clean slide

  2. Cut up an onion and separate it out into layers

  3. Peel off some epidermal tissue from the bottom of one of the layers

  4. Using tweezers, place the epidermal tissue into the water on the slide

  5. Add a drop of iodine solution
• Cover slip


  A square of thin, transparent plastic or glass placed on top of the specimen
• Use a light microscope to look at your slide

  1. Clip the slide you've prepared onto the stage

  2. Select the lowest-powered objective lens

  3. Use the coarse adjustment knob to move the stage up to just below the objective lens

  4. Look down the eyepiece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus

  5. Adjust the focus with the fine adjustment knob until you get a clear image

  6. If you need greater magnification, swap to a higher-powered objective lens and refocus
• You can work out the real size of a cell by counting the number of cells in 1 mm of the sample
• You can work out the magnification of your drawing using the formula: magnification = length of drawing / real length of cell