3.2.1.3 Methods of studying cells

• Resolution- ability to distinguish two points that are close together or far apart
• Light microscope uses visible light as source of illumination, can observe living cells
• Electron microscope- uses a beam of electrons on sample, no colour images, only dead cells
• Transmission electron microscope- beam of electrons through specimen to form an image
• Scanning electron microscope- beam scans over surface of specimen, 3D image created
• magnification= image size/ actual size
• 1. Homogenising cells- cells disrupted (cell membrane or cell wall broken), organelles released
• 2. Filtration- cell debris is removed from cell homogenate
• 3. Centrifugation- removal of organelles of different sizes and densities using different speeds
• Low resolution of light microscopes is caused by the long wavelength of visible light.
• Conditions that cell homogenate is kept in:

  • Using a buffer- keeps the pH the same so enzymes don't denature.
  • Ice cold- slows down the activity of enzymes to prevent the digestion of organelles.
  • Isotonic solution- prevents osmosis so lysis doesn't occur.