The Detective Work of Biology
The Detective Work of Biology
Every great biological discovery started with careful observation and experimentation. When Robert Hooke first observed cells in cork using his primitive microscope in 1665, he was doing exactly what you'll learn in these practicals - using scientific methods to unlock the secrets of life.
The three Required Practicals in Cell Biology will give you the essential skills every biologist needs: precise observation, controlled experimentation, and critical analysis of results.
Biology glossary
- What is the formula for magnification?
- Magnification = Image Size ÷ Actual Size
- What is the formula for percentage change in mass?
- Percentage change = ((Final mass - Initial mass) ÷ Initial mass) × 100
Magnification = Image Size ÷ Actual Size
Earn the mark scheme marks
Memory Aid: The MIR Triangle
Draw this triangle and memorise it — it appears in almost every biology paper:
[ I ]
[M x R]
Write I (Image size) in the top half of the triangle, and M (Magnification) and R (Real size) side by side in the bottom half.
- Cover I → Image size = M × R
- Cover M → Magnification = I ÷ R
- Cover R → Real size = I ÷ M
Unit conversion reminder:
"Milli to Micro — times by 1000" (1 mm = 1000 µm)
"Micro to Milli — divide by 1000" (1000 µm = 1 mm)
Stain colours mnemonic:
- Iodine = dark blue-Inky black (stains starch and cell walls)
- Methylene blue = blue nucleus (Makes the nucleus visible)
Now try it yourself
Quiz · Question 1 of 20
When using a light microscope to observe cells, which objective lens should be used first?
Tap an answer to check it
This topic in real past papers
Every real exam question we've found on cell biology practical investigations, with a full worked answer.
AQA Paper 1
Evaluate [data set] using information from the table and your own knowledge, or design/describe how an investigation should be carried out
AQA Paper 1
Describe how [an experiment] was carried out, name a control variable, or describe an aseptic technique used in a microbiology investigation