Studying Cells

• What methods are there to study cells?

  • Cell Fractionation
  • Light microscopes
  • Electron microscopes (TEM, SEM)
• How does cell fractionation work?

  1. Tissue cut into small pieces, placed into cold, isotonic, buffered solution
  2. Ground into smaller pieces using a Homogeniser, releasing organelles from cell
  3. Homogenate filtered to remove any complete cells & any cell debris (e.g. cell wall/membrane)
  4. Suspension of homogenate placed into a test tube and centrifuged
  5. ↓ speeds, larger fragments collect at bottom, smaller ones at top suspended in a liquid called supernatant liquid
  6. Larger fragments (sediment pellets) removed & process repeated: supernatant spun at faster speeds so smaller fragments can be recovered
• Why should the homogenate be:

  1. Cold- To reduce the activity of enzymes that break down organelles
  2. Isotonic- To prevent bursting or shrinking due to osmosis
  3. Buffered- To prevent pH fluctuations altering organelle & enzyme activity