Microscopy - OCR module 2.1

Microscopy - Module 2.1 - OCR

Microscopy is the study of biology through the use of a microscope.

For the exam, there are four microscopes to learn about in detail, which are to be paired with some theory and some cell microbiology which is only known to us through the use of microscopes. 

General Usage

Sample preparation has to be done in a specific order for efficency as well as using minimal prep product e.g. dye. 

Preparation

Stages are as following:

• Fixing
• Sectioning
• Staining
• Mounting

To remember this, you can use the anagram "Flowers Smell So Much".

Mounting the sample

When mounting the sample, there are a variety of different ways that the sample could be mounted, dependant on what sort of substance it is.

The techniques are as following:

• Dry mount

- Used for solid specimen.

- Cut into small, thin sections with use of a sharp blade

- Specimen placed on centre of slide with cover slide placed on top

• Wet mount

- This is when the specimen are suspended in a liquid like oil or water

- a cover slip is placed at an angle to avoid an artefact from being produced

- aquatic samples and living organisms can be viewed in this way

• Squash slide

- A wet mount is prepared first

- a lens tissue is used to press down the cover

- This is a good idea for soft samples e.g. root tips can be viewed this way

• Smear slide

- The edge of a slide is used to smear the sample across the slide

- This creates a thin, even coating on the slide

- A cover slip is placed on top

- This is perfect to view cells in the blood

Staining the sample

Resolution is limited by the wavelength of light and diffraction (diffraction is the bending of light as light passes through different mediums) of light as it passes through the sample. 

The cytosol of cells are also often transparent which limits how visible they are - even when magnified. 

Staining samples increases the contrast as different organelles will take up the stain to different degrees which means you will be able to not only see the cytosol but also be able distinguish between the organelles amongst this. 

To prepare a sample for staining, it is first placed on a slide and allowed to air-dry. This is then heat fixed by passing it through a flame. The specimen…