Required Practical: Microscopy (AQA GCSE Combined Science: Trilogy): Revision Note

Using a Light Microscope

• Aim: To use a light microscope to observe, draw and label a selection of plant and animal cells, including a magnification scale

• You will:

  • Use a light microscope to make observations of biological specimens and produce labelled scientific drawings

  • Include a magnification scale

Preparing a microscope slide

• Specimens must be prepared on a microscope slide to be observed under a light microscope

• This must be done carefully to avoid damaging any biological specimen

• The most common specimens to observe under a light microscope are cheek cells (animal cells) and onion cells (plant cells)

• Stains are used to highlight structures within cells – methylene blue is used to stain cheek cells, iodine for onion cells

Care must be taken to avoid smudging the glass slide or trapping air bubbles under the coverslip

Using a microscope

• Understanding the main features of a light microscope is essential if you are to use it correctly

• Always hold the microscope by the arm when moving it around the lab, and always start your observation with the lowest-powered objective lens

Light microscopes have a lens in the eyepiece which is fixed and two or three objective lenses of different powers

Biological drawings

• Producing biological drawings of what you see under the microscope is a key skill

• The key is not to try to be too artistic with your drawings – they are supposed to be scientific so make sure you follow the rules

Biological drawings should be as large as possible – aim to take up at least half of the space available on the page with your drawings