2.1.2- Slides And Photomicrographs
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What are ‘stains’?
They’re coloured chemicals that bind to molecules in or on the specimen, making the specimen easier to see.
Explain what differential staining is.
When some stains bind to specific cellular structures to stain each structure differently and can be identified within a single preparation.
Describe four examples of how differential staining can be utilised.
~Eosin stains cytoplasm. ~Sudan red stains lipids. ~Acetic Orcein binds to DNA and dark red stains chromosomes. ~Iodine in Potassium Iodine solution stains cellulose yellow and starch granules blue or black.
Explain how experts make ‘prepared and permanently fixes slides’.
• dehydrating the specimens • embedding them in wax- prevents distortion during slicing • make sections (v thin slices) that are stained and mounted in a special preserving chemical
What is the equation for linking actual size of a structure (A), the image size of the photomicrograph (I) and magnification (M)?
Magnification= Image Size/ Actual Size M=I/A
List the types of specimen that can be viewed using optical microscopes.
• Living Organisms- eg. Amoeba/ Paramecium • Smears preparations of human blood and cheek cells • Thin plant/ animal/ fungal tissue sections