Cell Structure Flashcards
Outline how a student could prepare a temporary mount of tissue for a light microscope.
1) Obtain a thin section of tissue
2) Place plant tissue in a drop of water
3) Stain tissue on a slide to make structures visible
4) Add a coverslip using mounted needle at 45 degrees to avoid trapping air bubbles
Describe how light microscopes work.
1) Lenses focus rays of light and magnify the view of a thin slice of specimen
2) Different structures absorb different amounts and wavelengths of light
3) Reflected light is transmitted to the observer via the objective lens and eyepiece
Describe how a transmission electron microscope works.
1) Pass a high energy beam of electrons through a thin slice of specimen
2) More dense structures appear darker since they absorb more electrons
3) Focus image onto the florescent screen or photographic plate using a magnetic lens
Describe how a scanning electron microscope works.
1) Focus a beam of electrons onto a specimens surface using electromagnetic lenses
2) Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
Describe how a laser scanning confocal microscope works.
1) Focus a laser beam onto a small area on a samples surface using objective lenses
2) Fluorophores in the sample emit photons
3) Photomultiplier tube amplifies the signal onto a detector. An image is produced pixel by pixel in the correct order
How should the field of view in microscopy be recorded?
Draw a diagram with a sharp pencil
include a scale bar
Annotate visible structures
Microscopy equation.
Magnification = Image/Actual
Define magnification.
Factor by which the image is larger than the actual specimen.
Define resolution.
Ability to distinguish between two objects.
Why do samples need to be stained for light microscopes?
- Coloured dye binds to the structures
- Facilitates absorption of wavelengths of light to produce image.
What is differential staining?
Contrast between heavily and lightly stained areas distinguishes structures
State the maximum magnification and resolution of a light microscope.
Magnification = x1500
Resolution = 200nm
State the magnification and resolution of a transmission electron microscope.
Magnification = x500,000
Resolution = 0.1 nm
State the magnification and resolution of a scanning electron microscope.
Magnification = x100,000
Resolution = 0.1 nm
Explain how to use an eyepiece graticule and stage micrometer to measure the size of a structure.
1) Place micrometer on stage to calibrate eyepiece graticule
2) Line up scales on graticule and micrometer. Count how many graticule divisions are in 100 micrometers on the micrometer
3) Length of 1 eyepiece division = 100 micrometers/ number of divisions
4) Use calibrated values to calculate actual length of structures.
