Biology Topic 2.1.1 - Microscopy (Preparing samples + staining) Flashcards
How should you prepare your specimen when it is a liquid? = Dry Mount
- Add a few drops of the sample to the slide using a pipette
- Cover the liquid/smear with a coverslip placed at an angle (to push any air to the sides and reduce air bubbles), and gently press down toremove air bubbles.
- Wear glovesto ensure there is no cross-contamination of foreign cells.
How should you prepare your specimen when it is solid? = Wet Mount
- Use scissors to cut a small sample of the tissue.
- Peel away or cut avery thin layerof cells from the tissue sample to be placed on the slide (using a scalpel or forceps)
* The tissue needs to be thin so that thelightfrom the microscope can pass through - Apply a stain if needed
- Gently place a coverslip on top and press down to remove any air bubbles.
How should you prepare your specimen when using squashing slides?
Squash slides – a wet mount is prepared then a lens tissue is used to gently press down on the cover slip (or between two slides). Good for looking at soft samples e.g. root tip squashes are used to look at cell division.
How should you prepare your specimen when using smear slides?
Smear slides – the edge of the slide is used to smear the sample. It creates a thin, even coating on another slide. A cover slip is placed over the sample. E.g. looking at blood cells on a blood smear slide.
Why do we stain samples?
Sometimes the object ebing viewed under the microscope is compltely transparent. This makes teh whole thing look white because the light rays just pass straight through. To overcome this, the objects can be stained.
How should you stain samples for a light microscope?
For a light microscope, this means using some kind of dye. Common stains include methylene blue or eosin.
The stain is taken up by some parts of the object more than others - the contrast makes the different parts show up.
What does the stain iodine show? What type of cells is it used on? What colour does it become?
Stains carbohydrates in plant and animal specimens brown or blue- black. Stains glycogen red.
What does the stain methylene blue show? What kind of cells is it used on? What colour does it become? What kind of stain is it?
Stains acidic cell parts (like nucleus) blue. Use on animal, bacteria and blood specimens. In low concs it can safely be used on living tissue. It is called a vital stain.
What does the stain Eosin Y show? What type of cells is it used on? What colour does it become?
What is a substitute for?
Stains alkaline cell parts (like cytoplasm) pink. Use on plants,animals and blood. Can be used as a substitute for Congo Red and Carmine
What does the stain safranin show? What type of cells is it used on? What colour does it become?
Mainly used for sections of plant tissues, stains red
What does the stain Toluidine Blue show? What type of cells is it used on? What colour does it become?
Stains acidic cell parts (like nucleus) dark blue. Good to show mitosis in plant cells.
What does the stain Wright’s Stain show? What type of cells is it used on? What colour does it become?
Stains red blood cells pink/red.
What does the stain Leishman’s Stain show? What type of cells is it used on? What colour does it become?
Stains nucleus of WBC blue and blood cells pink
What does the stain Crystal Violet show? What type of cells is it used on? What colour does it become?
Stains bacteria purple
What does the stain Aceto-orcein show? What type of cells is it used on? What colour does it become?
Biological stain for chromosomes and connective tissue.
