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Practical 1Spec ref: B1a.5

Microscopy

Linked to B1: Cell Biology

Aim

Prepare, observe, draw and label animal and plant cells using a light microscope.

PDF Resources

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Practical Guide

Method & analysis

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Exam Questions

Past-paper style

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Mark Scheme

Model answers

Equipment

  • •Light microscope
  • •Glass slides and coverslips
  • •Forceps and scalpel
  • •Iodine solution (plant cells)
  • •Methylene blue (animal cells)
  • •Onion
  • •Distilled water

Variables

Independent variable
Type of stain / magnification used
Dependent variable
Appearance of cells as viewed under microscope
Controlled variables
Same light microscope, same preparation technique

Key Facts to Know

✓Magnification = Image size ÷ Actual size
✓1 mm = 1000 µm — convert before calculating
✓Light microscope max ~x1500 magnification, ~200 nm resolution
✓Electron microscope: ~0.1 nm resolution — reveals organelles in detail
✓Resolution = ability to distinguish two separate points

⚠️ Common Mistakes

  • ✗Confusing magnification (bigger image) with resolution (more detail)
  • ✗Forgetting to convert mm to µm before calculating actual size
  • ✗Not showing working in magnification calculations

💡 Exam Tips

  • ★Always show the magnification formula and substituted values
  • ★State units — actual cell size should be in µm
  • ★For Higher: explain why electron microscopes have better resolution than light microscopes

All Required Practicals

Practical 1Practical 2Practical 3Practical 4Practical 5Practical 6Practical 7Practical 8
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