REQUIRED PRACTICLES

• Optical microscope

  Used to look at cells on a prepared microscope slide
• Optical microscope

  • Has a stage to place the microscope slide
  • Has a light source (lamp or mirror) to illuminate the slide
  • Has objective lenses with different magnifications (4x, 10x, 40x)
  • Has an eyepiece lens with 10x magnification
  • Has coarse and fine focusing dials
• Using an optical microscope to view a prepared slide

  1. Place slide on stage and secure with clips

  2. Select lowest power (4x) objective lens

  3. Slowly turn coarse focus dial to lower lens near slide

  4. Look through eyepiece and turn coarse focus dial to bring cells into focus

  5. Use fine focus dial to sharpen focus

  6. Calculate total magnification by multiplying eyepiece (10x) and objective (4x, 10x, 40x) lens magnifications
• What can be seen under an optical microscope

  • Animal cells: nucleus, cytoplasm, cell membrane, possible mitochondria
  • Plant cells: cell wall, cytoplasm, nucleus, possible vacuole and chloroplasts
• Optical microscopes have limited detail - cannot see organelles like ribosomes or lysosomes
• Drawing of cells should include a magnification scale, measured by placing a ruler on the stage
• Osmosis

  Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Plant cells placed in water

  Water moves into the cell by osmosis, causing the cell to expand
• Plant cells placed in concentrated solution

  Water moves out of the plant cell by osmosis, causing the cell to shrink
• Investigating the effect of osmosis on plant tissue

  1. Peel potato

  2. Use cork board to produce cylinders

  3. Trim cylinders to same length

  4. Measure length and mass of cylinders

  5. Place cylinders in test tubes with different solutions

  6. Leave overnight

  7. Remove cylinders, gently roll on paper towel

  8. Measure length and mass of cylinders again
• Distilled water

  Contains no dissolved substances that could affect the weight of osmosis
• Percentage change

  Calculated as: (change in value / original value) x 100
• Concentration of sugar solution

  Affects percentage change in mass or length of potato cylinder
• Graph of percentage change vs sugar solution concentration shows water moving in/out of cell by osmosis