Microscopy Flashcards
Describe, in principle, what a microscope does. (F)
An instrument which enables you to magnify an object
Name 4 different types of microscope. (F)
- Light Microscope
- Transmitting Electron Microscope (TEM)
- Scanning Electron Microscope (SEM)
- Laser Scanning Confocal Microscope (LSCM)
State what “SEM” and “TEM” are abbreviations for. (F)
- Scanning Electron Microscope
- Transmitting Electron Microscope
Outline how an SEM works.
- beam of electrons sent across surface of specimen
- reflected electrons are collected
Outline how a TEM works.
- beam of electrons transmitted through a specimen
- focused to produce an image
Outline how a laser scanning confocal microscope works.
- single spot of focused light (laser) moved across a specimen (point illumination)
- causes fluorescence from components labelled with “dye”
- emitted light from specimen filtered through pinhole aperture
Describe the use and properties of light microscopy. (F)
Use:
- easily available
- can be used out in field
Properties:
- relatively cheap
- can view living/dead specimens
Describe the use and properties of SEM. (F)
Use:
- can produce images with high magnifications and clear resolution
Properties:
- dead specimens (vacuum)
- can see more detail of cell ultrastructure
Describe the use and properties of TEM. (F)
Use:
- can produce images with high magnifications and clear resolution
Properties:
- dead specimens (vacuum)
- can see more detail of cell ultrastructure
Describe the use and properties of LSCM. (F)
Use:
- diagnosis of diseases of the eye and endoscopic procedures
- used for drug development
- virtual biopsies
Properties:
- living/dead specimen
- can see distribution of molecules within cells
- non-invasive
State the features of the images produced from light microscopes.
- true colour
- living/dead specimen
- halide stains (?)
- 2D image
State the features of the images produced from SEM.
- false colour
- dead specimen (vacuum)
- heavy metal stains
- high magnification and resolution
- 3D image
State the features of the images produced from TEM.
- false colour
- dead specimen (vacuum)
- heavy metal stains
- high magnification and resolution
- 2D image
State the features of the images produced from LSCM.
- true colour
- living/dead specimen
- fluorescent dye
- 2D/3D (can scan in layers)
Explain how to use a light microscope to view a specimen at low and high powers.
- change the objective lens to a different power
- adjust resolution with coarse and fine focusing knob
Describe how to produce a temporary wet mount of living tissue.
- suspend specimen in liquid (e.g. water or an immersion oil)
- place a cover slip on from an angle
Describe and explain the characteristics of a good slide preparation.
- suitable stain so can differentiate between different parts of the sample
- no air bubbles
- evenly and well stained
- thin specimen
- no artefacts
Explain why slide preparations need to be thin. (F)
- so light can shine through
- details can be seen
Explain how to use a stage micrometer to work out the distance represented by the small divisions in an eyepiece graticule under 3 different objective lenses. (F)
1 graticule division = number of micrometres/number of graticule divisions
Explain how to use a stage micrometer and eye-piece graticule to add a scale bar to a drawing.
- measure feature of speciment with eyepiece graticule
- convert to micrometres using calibration done with stage micrometer
- draw scale bar on drawing, matching the length of the feature you measured and label with micrometres
Explain how to use a stage micrometer and eye-piece graticule to calculate the size of a specimen.
graticule divisions x magnification factor = measurement
Describe how to choose an appropriate number of significant figures, or decimal places to present data.
Use the same decimal places/significant figures as all of the other data is given in
Explain how an adjustment to the “plane of focus” can alter what is viewed within a cell. (F)
Because a cell is 3D, the shapes can look different from different angles i.e. the mitochondria is sausage shaped, but can appear spherical if viewed from the end.
Explain how a tissue slice might be misleading due to the very thin nature of the slice.
Can be distorted.
