MicroscopyEdexcel International A Level Biology: Flashcards
What these 14 flashcards ask
- Write the magnification equation.
- Define resolution.
- Why does an electron microscope have a higher resolution than a light microscope?
- What is the resolution of a light microscope?
- Give two advantages of a light microscope.
- How does a TEM form an image?
- How does an SEM differ from a TEM?
- What is an artefact?
- Why are specimens stained?
- What stain shows starch?
- How do you calibrate an eyepiece graticule?
- Why recalibrate when the objective lens is changed?
- State four rules for a biological drawing.
- How many micrometres are in 1 mm?
Exam questions on Microscopy
- A scientist photographs a human liver cell using a transmission electron microscope (TEM). The micrograph is printed at a magnification of ×15 000. On the micrograph the diameter of the cell measures 300 mm and the length of one mitochondrion measures 45 mm.Calculate the actual length of the mitochondrion. Give your answer in micrometres (µm).2 marks
- A student prepares temporary mounts of onion epidermis and of potato tissue to view with a light microscope. In an unstained mount the cells are almost transparent and few structures can be seen.Explain why a stain is added to the onion epidermis before it is viewed.2 marks
- A student calibrates an eyepiece graticule using a stage micrometer, which is a slide marked in divisions of 10 µm. With the ×40 objective lens, 80 divisions on the eyepiece graticule line up exactly with 40 divisions on the stage micrometer. The student then measures the length of a stained onion epidermis cell as 14 graticule divisions.Calculate the actual length of the onion cell. Show your working.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).