Why Do We Use Stains?
Part of Cell Biology Practical Investigations — GCSE Biology
This how it works covers Why Do We Use Stains? within Cell Biology Practical Investigations for GCSE Biology. Comprehensive practical skills, experimental design, data analysis, microscopy techniques, and scientific methodology in cell biology It is section 9 of 17 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 9 of 17
Practice
20 questions
Recall
20 flashcards
Why Do We Use Stains?
Under a light microscope, most cell structures appear almost completely transparent and colourless. Without staining, you would look at a glass slide and see very little — the cell contents blend into the surrounding water or mounting medium.
Stains work by binding to specific chemical structures within cells, adding contrast so those structures become visible. Different stains are selective — they bind to different types of molecules:
- Iodine solution binds to starch and reacts with cell wall components, turning them dark blue-black. It is ideal for staining plant cells (e.g., onion epidermis) because it reveals the cell wall, cytoplasm, and nucleus clearly.
- Methylene blue binds to nucleic acids (DNA and RNA), which are acidic molecules. It stains the nucleus a deep blue colour, making it clearly visible in animal cells such as cheek cells, where the cell wall is absent.
- Toluidine blue (used in the mitosis practical) stains chromosomes, making stages of mitosis easier to identify.
It is important to understand that stains do not magnify structures — they only add colour. Resolution and magnification are separate concepts determined by the quality of the microscope lenses, not the stain used.