7981805
Descripción
Mapa Mental por Aleena Sheraz, actualizado hace más de 1 año
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Creado por Aleena Sheraz
hace casi 8 años
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2.1.2 Slides and photomicrographs
- Optical microscopes are used to view a
wide range of specimens
- Living organisms like
paramecium and amoeba
- Smear preparations of human
blood and cheek cells
- Thin sections of animal, plant or
fungal tissue e.g. bone, muscle,
leaf, root or fungal hyphae
- Living organisms like
paramecium and amoeba
- Observing unstained specimens
- Many biological structures are
colourless and transparent
- Some microscopes use light interference
rather than light absorption = produces a
clear image without staining
- Some microscopes use a dark backdrop
against the illuminated specimen
- Useful for studying living specimens
- Many biological structures are
colourless and transparent
- Staining specimens
- Stains= coloured chemicals that bind to
molecules on/in the specimen making it
easy to see
- Methylene blue = all purpose stain
- Differential staining= some stains bind to specific structures
staining them each differently to be identified
- Acetic orcein = binds to DNA, stains
chromosomes dark red
- Eosin = stains cytoplasm
- Sudan red= stains lipids
- Iodine (in potassium iodide
solution)= stains cellulose in
plant walls yellow and starch
granules blue/black
- Stains= coloured chemicals that bind to
molecules on/in the specimen making it
easy to see
- Observing prepared specimens
- Permanently fixed slide are made
by experts in labs by:
- Dehydrating specimens
- Embedded in wax to prevent distortion when slicing
- Special instrument makes v. thin slices (sections) which
are stained and mounted in a special chemical to
preserve them
- Special instrument makes v. thin slices (sections) which
are stained and mounted in a special chemical to
preserve them
- Embedded in wax to prevent distortion when slicing
- Dehydrating specimens
- Permanently fixed slide are made
by experts in labs by:
- Calculations involving magnification
- If you know the magnification on a
photomicrograph, you can work out the actual
size of the strucutres
- Measure the widest part in mm
- Convert to um by X1000
- Divide this by magnification
(tells you actual size)
- Divide this by magnification
(tells you actual size)
- Convert to um by X1000
- Measure the widest part in mm
- If you are told actual size of a structure on a
photomicrograph and you measure the image
size in um, you can calculate magnification
factor
- M: I/A
- M= magnification factor
- I= Image size, um
- A= actual size
- A= actual size
- If magnification factor is 1000 it
must be written as X1000
- I= Image size, um
- M= magnification factor
- M: I/A
- If you know the magnification on a
photomicrograph, you can work out the actual
size of the strucutres
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