A student looks at onion epidermis cells using a light microscope.
Onion epidermis cells are colourless. The student adds a drop of iodine solution to the cells.
Explain why.
The student places a cover slip on top of the cells.
Give one reason why.
The diameter of the field of view is 0.5 mm. The student counts 10 cells side by side across the diameter of the field of view.
Estimate the width of one cell.
Give your answer in μm\mu\text{m}μm.
Suggest why the answer to (c) is only an estimate.
130 exam-style questions on OCR GCSE Biology 1.1 Cell structures, covering 1.1.1 Viewing cells with light microscopes, 1.1.2 Sub-cellular structures and functions, and 1.1.3 Electron microscopy and resolution. Each one has a worked solution and a mark scheme showing where the marks go.