2.1.2 Slides & Photomicrograph Flashcards
How are you able to observe unstained specimens?
Microscopes use light interference in order to produce a clear image without staining. Some microscopes use a dark background against which the illuminated specimen shows up.
What are chemical stains?
Coloured chemicals that bind to molecules in or on the specimen, making the specimen easy to see.
Provide an example of an all-purpose stain.
Methylene blue
What is differential staining?
Stains that bind to specific cell structures produce different staining for each structure so the structures can be easily identified within a single preparation.
What stain binds to DNA and what colour does it produce?
Acetic orcein binds to DNA and stains chromosomes dark red.
What stains cytoplasm?
Eosin
What stains lipids?
Sudan red
What does the iodine in potassium iodide solution stain?
- Stains the cellulose in plant cell walls yellow
- stains starch granules blue/black (will look violet under the microscope)
How are specimens prepared to be viewed on slides?
- Specimens are dehydrated
- They are then embedded in wax to prevent distortion during slicing
- Thin slices, called sections, are then created
- Sections are stained and mounted in a chemical to preserve them
How do you calculate using magnifications (e.g. on a photomicrograph) to find the actual size of the structures?
- Measure the widest part of the specimen on the photomicrograph in mm.
- Convert that measurement to μm by multiplying by 1000
- Divide this figure by the magnification
What is the formula to calculate the magnification factor and what are the units?
- M= I/A where M is the magnification factor, I is the image size on the photomicrograph in μm (mm x 1000), and A is the actual size of the structure on a photomicrograph
- There are no units for magnification by if the magnification factor is 1000, then you must write it as x1000
