PAG01 = MICROSCOPY Flashcards
What are stages of using a microscope?
Calibrating the graticule; prepare slides; use microscope; measure size; drawings
What is an eyepiece graticule?
acts as a rular, to measure structures under the microscope
What is a stage graticule (stage micrometre) ?
microscope slide with an accurate measuring scale- calibrates the value of eyepiece divisions.
How do you calibrate an eyepiece graticule?
- set up microscope
- place stage graticule on stage
- line up the two scales (stage and eyepiece)
- count the no. of divisions of eyepiece grat compared to stage grat
- calculate the length of one eyepiece grat division
What needs to be remembered when calibrating?
if you change the magnification of the microscope, the eyepiece graticule must be
re-calibrated!
What is staining?
contrast to distinguish between different structures in the sample
What is differential staining?
multiple stains are used, and each stain binds to a
specific cell structure, staining each structure differently so the structures can be easily
identified.
What binds to DNA and stains
chromosomes dark red ?
Acetic orcein
What stains cytoplasm dark red or pink?
Eosin
What stains starch blue-black (appears
violet under the microscope)
Iodine
What stains cellulose yellow?
Iodine in potassium iodine solution
What stains RNA/DNA a purple/blue colour
Haematoxylin
What is is an all-purpose stain, used often to stain DNA blue?
Methylene blue
How do you do a wet mount?
a) Use a pipette to put water on the slide.
b) Use tweezers to place the specimen in the water.
c) Put the cover slip on by standing it upright on the slide, next to the water droplet,
then carefully tilt it down onto the specimen. not add bubbles – these
will obstruct the view of the image.
d) Add a stain. Put a drop on one edge of the cover slip. Put a paper towel on the
opposite edge. The paper towel will absorb the stain, drawing it under the
coverslip,
What is a dry mount technique?
a) Slice the specimen into a thin piece so light can pass through
b) Use tweezers to pick it up and put it in the middle of the slide
c) Put a cover slip on top of it.
How do you use a light microscope?
- Clip the slide onto the stage
- Select the lowest-powered objective lens
- Use the coarse adjustment knob to move the objective lens to just above the slide.
- Look down the eyepiece and adjust the focus by using the fine adjustment knob, until a clear image appears. Note: always adjust the
focus by moving the lens away from the slide – this prevents you from moving the
lens too close to the slide and breaking it - If a higher magnification is needed, swap to a higher-powered objective lens and
refocus
How do you measure the size of a cell with a microscope?
measured by counting the number of eyepiece divisions. To find the actual length, the number of divisions should be multiplied by the length of one division
What are things to remember when drawing cells?
● No shading. Areas that should be shaded should be labelled instead.
● The drawing should take up at least half of the page.
● Label lines must be completely horizontal, drawn with a ruler, exactly touch the
object that they’re labelling and must not overlap each other.
● A scale should be given
● They should be drawn in pencil and look like the actual image.
