Topic: Using a microscope
Sample preparation
Solid specimens Dry mount - Solid specimens are viewed whole or cut into very thin
are viewed whole sections. The sample is placed on the centre of the slide and a cover
or cut into slip is placed over the sample. Things such as hair, pollen, dust and
sections in a dry insect parts can be viewed whole. Muscle or plant tissue can be
mount sectioned and viewed this way.
Specimens are Wet mount - Specimens are suspended in liquid such as water or an
suspended in immersion oil. A cover slip is placed at an angle to prevent air bubbles
liquid in a wet abstracting the sample. Aquatic organisms can be viewed this way.
mount
A wet mount is Squash slides - A wet mount is prepared then lens tissue is used to
gently pressed gently press down the cover slip. This technique can be used to
down in a squash observe cell division in root tips.
slide
The sample is Smear slides - The edge of the slide is used to smear the sample
smeared in a evenly to create a thin coat. This is a good way to observe cells in
smear slide blood.
Staining
Samples are Stains are used to increase contrast and to be able to distinguish
stained to between organelles which are naturally transparent.
increase contrast
Staining for light microscopy
Coloured dyes - Coloured dyes are used to stain make tissues visible
add colour to - The dyes absorb and reflect certain colours of light, certain
make tissues tissues absorb certain dyes depending on their chemical
visible nature
- Samples can be stained with multiple dyes to make different
tissues visible under a light microscope, this is known as
differential staining
Examples of stains
- Methylene blue - used particularly for DNA
- Eosin - used to see cytoplasms
- Iodine
Staining for electron microscopy
Dyes are used to - Specimen used in TEMs must must be stained in order to
absorb electrons absorb electrons
- Electrons have no colour so the dyes used for staining show
up black or different shades of grey
- Heavy metal compounds are used as dyes as they absorb
electrons well
Examples of stains
- Osmium tetroxide
- Ruthenium tetroxide
Sample preparation
Solid specimens Dry mount - Solid specimens are viewed whole or cut into very thin
are viewed whole sections. The sample is placed on the centre of the slide and a cover
or cut into slip is placed over the sample. Things such as hair, pollen, dust and
sections in a dry insect parts can be viewed whole. Muscle or plant tissue can be
mount sectioned and viewed this way.
Specimens are Wet mount - Specimens are suspended in liquid such as water or an
suspended in immersion oil. A cover slip is placed at an angle to prevent air bubbles
liquid in a wet abstracting the sample. Aquatic organisms can be viewed this way.
mount
A wet mount is Squash slides - A wet mount is prepared then lens tissue is used to
gently pressed gently press down the cover slip. This technique can be used to
down in a squash observe cell division in root tips.
slide
The sample is Smear slides - The edge of the slide is used to smear the sample
smeared in a evenly to create a thin coat. This is a good way to observe cells in
smear slide blood.
Staining
Samples are Stains are used to increase contrast and to be able to distinguish
stained to between organelles which are naturally transparent.
increase contrast
Staining for light microscopy
Coloured dyes - Coloured dyes are used to stain make tissues visible
add colour to - The dyes absorb and reflect certain colours of light, certain
make tissues tissues absorb certain dyes depending on their chemical
visible nature
- Samples can be stained with multiple dyes to make different
tissues visible under a light microscope, this is known as
differential staining
Examples of stains
- Methylene blue - used particularly for DNA
- Eosin - used to see cytoplasms
- Iodine
Staining for electron microscopy
Dyes are used to - Specimen used in TEMs must must be stained in order to
absorb electrons absorb electrons
- Electrons have no colour so the dyes used for staining show
up black or different shades of grey
- Heavy metal compounds are used as dyes as they absorb
electrons well
Examples of stains
- Osmium tetroxide
- Ruthenium tetroxide
