Required practical 1: using a light microscope

Cell biology · Cell structure · note 3 of 6

Spec 4.1.1.2Download all Cell structure notes (PDF)Download all notes (PDF)9 pages

Required practical 1: using a light microscopeSpec 4.1.1.2

In short

Required practical 1 uses a light microscope to observe, draw and label plant and animal cells. Mount thin tissue on a slide with water or a stain and a cover slip, focus on the lowest-power objective with the coarse focusing knob, then sharpen with the fine knob. Total magnification is the eyepiece lens magnification multiplied by the objective lens magnification.

Required practical:

Use a light microscope to observe, draw and label a selection of plant and animal cells. A magnification scale must be included.

Place a thin piece of tissue (for example onion epidermis, or cheek cells) on a clean microscope slide. Add a drop of water or a stain such as iodine solution.
Lower a cover slip onto the specimen at an angle, using a mounting needle, so that no air bubbles are trapped.
Clip the slide onto the stage. Select the lowest-power objective lens and turn the coarse focusing knob until the specimen is roughly in focus.
Use the fine focusing knob to get a sharp image. Then switch to a higher-power objective lens and refocus with the fine focusing knob only.
Draw what you see using a sharp pencil. Use clear, unbroken lines, no shading, and make the drawing large. Draw only a few cells accurately rather than many badly.
Label the sub-cellular structures with straight label lines that do not cross. Add a title and the magnification.

To find the total magnification of a light microscope, multiply the magnification of the eyepiece lens by the magnification of the objective lens. The magnification of your drawing is found with the equation magnification = size of image ÷ size of real object, using the width of your drawing and the real width of the cell.

Safety: carry the microscope with two hands, handle glass slides and cover slips carefully, and take care with the stain, which can mark skin and clothes. Start with the lowest-power lens so that the objective lens does not hit the slide.

Exam tip:

A scale or magnification must be included on a drawing. Always write the magnification next to the title, for example 'Onion cells, × 400'.

Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026

Frequently asked questions

What is the difference between prokaryotic and eukaryotic cells?

Eukaryotic cells, such as plant and animal cells, have their genetic material enclosed in a nucleus. Prokaryotic cells, such as bacteria, are much smaller and their genetic material is not in a nucleus. It is a single DNA loop, and there may be plasmids. Both types of cell have a cell membrane and cytoplasm.

Why do plant cells have a cell wall?

Plant cells have a cell wall made of cellulose because it strengthens the cell. Animal cells do not have a cell wall. Plant cells also often have a permanent vacuole filled with cell sap, which helps keep the cell firm, and chloroplasts, which contain chlorophyll to absorb light energy for photosynthesis.

How do you calculate magnification in biology?

Magnification is calculated with magnification = size of image ÷ size of real object. Make sure both measurements are in the same units before you divide. Rearranged, real size = image size ÷ magnification. For a light microscope, the total magnification is the eyepiece lens magnification multiplied by the objective lens magnification.

All 4 questions on Cell structure