Analysis of cell components

• What is the equation for magnification?

  magnification = size of image/size of real object
• What are the two types of microscopes?

  Light and electron microscope
• What are the two types of electron microscopes?

  TEM and SEM
• What is an advantage of a TEM microscope?

  Gives high resolution images, so shows small objects
• What is a disadvantage of a TEM microscope?

  Can only be used on thin specimen. Can only be used on non living specimens
• What is an advantage of a SEM microscope?

  Can be used on thick specimens. Can be 3-d
• What is a disadvantage of a SEM microscope?

  Gives lower resolution images then TEM. Can only be used on non-living specimens
• What are microscope artefacts?

  Things that you can see through the microscope that isn't part of the cell.
• What are examples of microscope artefacts?

  Dust, air bubbles and fingerprints
• What is cell fractionation?

  Breaking down of a cell to see organelles
• What are the three stages of cell fractionation?

  • Homogenisation - Breaking up the cells
  • Filtration - Getting rid of the big bits
  • Ultracentrifugation - Separating the organelles
• Explain the process of Homogenisation

  Vibrating or grinding cells in blender breaks up the plasma membrane and releases organelle into solution.
• Why should the homogenisation solution be kept in ice cold?

  To reduce enzyme activity that break down organelles
• Why should homogenisation solution be buffered?

  To maintain and control the pH balance
• Why should homogenisation solution should be at the same water potential?

  To stop organelles from bursting due to osmotic gain/loss
• Explain the process of filtration

  Homogenised cell solution filtered through a gauze to separate any large cell debris or tissue debris
• Explain the process of ultracentrifugation

  • Cell fragments poured into tube and spun in centrifuge at a low speed
  • Heaviest organelle like nuclei become pellets at the bottom of the tube.
  • Rest of organelle stay suspended in the fluid above the pellet - the supernatant
  • Supernatant drained off and poured into another tube and spun in the centrifuge at a higher speed
  • Again the heaviest organelle becomes a pellet at the bottom of the tube . Supernatant containing the rest of the organelle is drained and spun in an even higher speed.
  • This cycle is repeated till all organelles are separated out.
• State the organelle order of mass ( from heaviest to lightest)

  Nuclei, mitochondria, lysosomes, endoplasmic reticulum, ribosomes