B1.1.3 light microscopes Flashcards
What does the symbol µm mean?
Micrometre
1,000,000 µm in a metre
What are the seven life processes?
Movement, reproduction, sensitivity, growth, respiration, excretion, nutrition
What are examples of prokaryotes(single-celled organisms without a nucleus)?
- Escherichia coli(E.coli) - causes food poisoning
- Streptococcus bacteria - causes sore throats
- streptomycin bacteria - found in the soil
What is a light microscope?
Used to observe small structures in detail
The microscope passes light through an object places on a slide on the stage, then through 2 glass lenses(objective lens, eyepiece lens). The lenses magnify the object so we can see it in more detail when viewing through the eyepiece.
Total Magnification formula:
Total magnification = eyepiece lens magnification x objective lens magnification
Parts to a light microscope:
- eyepiece lens
- objective lens
- coarse focus
- fine focus
- light
- stage
- slide
How can you observe cells through a microscope?
1) move the stage to it’s lowest position
2) select the objective lens with the lowest magnification
3) place the slide, which has cells on it, on the stage
4) turn the coarse focus knob slowly until you see your object (blurred)
5) turn the fine focus knob slowly until your object comes into clear focus
6) to see the cells in greater detail, repeat steps using a higher magnification objective lens
Why stain cells?
Many cells are colourless
Scientists stain them to make them easier to observe
Some colour the whole cell, others highlight specific subcellular structures
How do you apply a stain?
1) place the cells on a glass slide
2) add one drop of stain
3) place a coverslip on top
4) tap the coverslip gently with a pencil to remove air bubbles
Common stains used:
- methylene blue - makes it easier to see the nucleus of an animal cell
- iodine solution - makes it easier to see plant cell nuclei
- crystal violet - stains bacteria cell walls
Formula of actual cell size
Actual cell size= image size/magnification
