Methods of studying cells

• Units of measurement (highest to lowest)

  • kilometre
  • metre
  • millimetre
  • micrometre
  • nanometre
• Magnification = how much bigger the image is than the actual specimen
• Resolution = ability to distinguish between two points that are close together as separate structures
• Magnification = image size / actual size
• Light has a longer wavelength so has lower resolution
• Electrons have shorter wavelength and so have high resolution
• Before breaking open cells, tissue is placed in solution

  • cold = slow/stop enzyme activity to not damage organelles
  • isotonic = same water potential as cells to prevent osmosis
  • buffered = maintain constant pH so proteins don't denature
• Cell fractionation and ultracentrifugation

  • place tissue/cells in cold, isotonic, buffered solutions
  • tissue and cells broken up in homogeniser
  • filter to remove large debris and unbroken cells
  • spin homogenate at low speed in a centrifuge - heaviest organelles form pellet
  • repeat centrifugation at higher speeds using the supernatant to remove next organelles