2.1.1 Studying Cells

• What is the primary use of microscopes in studying cells?

  To observe and investigate cell structure
• What are the different types of microscopes used to study cells?

  • Light microscopes
  • Electron microscopes
• How do the images generated by different types of microscopes differ?

  They differ significantly in detail and resolution
• What do light microscopes use to form an image?

  Light
• What is the maximum resolution of a light microscope?

  0.2 micrometres (µm)
• What is the maximum useful magnification of optical microscopes?

  About x1500
• What can light microscope images reveal about cells?

  Cell shape and larger internal structures
• What do electron microscopes use to form an image?

  Electrons
• What is the maximum resolution of an electron microscope?

  0.0002 µm or 0.2 nm
• What is the maximum magnification range of electron microscopes?

  From around ×1,000,000 up to many millions
• What small structures inside cells can electron microscopes observe?

  • Cell membranes
  • Ribosomes
  • Endoplasmic reticulum
  • Lysosomes
• What are the limitations of electron microscopes?

  • Very large and expensive
  • Complex specimen preparation
  • Specimens viewed in a vacuum (no live specimens)
  • Images are black and white (can be artificially colored)
• What are the two types of electron microscopes?

  • Transmission electron microscopes (TEMs)
  • Scanning electron microscopes (SEMs)
• How do transmission electron microscopes (TEMs) create images?

  By transmitting a beam of electrons through a specimen
• What are the characteristics of images produced by TEMs?

  • High-resolution
  • Allow internal structures to be seen
  • Two-dimensional
• How do scanning electron microscopes (SEMs) create images?

  By passing a beam of electrons across the surface of a specimen
• What are the characteristics of images produced by SEMs?

  • Three-dimensional
  • Show the surface of specimens
• How does the maximum resolution of SEMs compare to TEMs?

  SEMs have a lower maximum resolution than TEMs
• What should students be prepared for in an exam regarding microscope images?

  • Identifying the microscope used to produce an image
  • Understanding differences between images from different microscopes