Methods of studying cells

• Light microscope

  
• Electron microscope exposes a specimen to electrons instead of light
• There are two types of electron microscopes ; scanning and transmission
• Specimens are coated with a thin layer of metal such as gold, platinum or tungsten to improve conductivity and contrast
• Electrons don’t pass through the stained parts because they are absorbed
• Limitation of electron microscope:

  • cannot look at living material as in a vacuum
  • Image is only 2D
  • Specimen must be very thin
  • Specimens take a lot of time to prepare
• Cell fractionation - a process where cells are broken up to release the different organelles , they are separated based on their size
• Cell fractionation :

  • Homogenisation
  • Filtration
  • Ultracentrifugation- separating the organelles
• Homogenisation – breaking down the cell membrane using a homogeniser, which breaks it into small pieces
• Filtration – passing the mixture through a series of filters with decreasing pore sizes until all but one type of particle has been removed.
• Ultracentrifuge – spinning the sample at high speeds so that heavier particles sink faster than lighter ones
• Magnification is the size of an image compared to the real object
• Resolution is ability to distinguish between two separate objects that are close together