2.1.1 Studying Cells Flashcards
Magnification definition
How many times bigger an image produced by the microscope is than the real life object
Resolution definition
Ability to distinguish between 2 points that are close together
Adv and Disadv of light microscopes
About :
- Impossible to resolve between 2 objects closer than half the wavelength of light (500-650nm)
-Adv :
- Small and easy to carry
- Cheap
- Easy sample preparation
- Easy to use
- Specimens can be alive or dead eukaryotic cells
- No vacuum needed
- Colour image
Disadv :
- Max resolution 200nm
- Max magnification 1500
- Cannot observe ribosomes, lysosomes or endoplasmic reticulum
Adv and Disadv of Transmission Electron Microscopes. How do they work?
Focus beam of electrons through specimen. denser parts absorb more electrons so appear darker on final image. Produces contrast between different parts of specimen.
Adv :
- High resolution
- Internal structures within cells can be seen
- High magnification
Disadv :
- Only thin specimens
- Cannot observe live specimens
- Vacuum needed
- Water must be removed from specimen
- Artefacts may be introduced due to lengthy preparation of specimens
- Not a colour image
Adv and Disadv of scanning electron microscopes. How do they work?
Scan beam of electrons over specimen. Electrons bounce of surface and detected to form an image
Adv :
- 3D external structures of specimen can be observed
- Thick or 3D specimens used
Disadv :
- Lower resolution than TEMs
- Cannot observe live specimens
- No colour
What are laser scanning confocal microscopes? Advantages and Disadvantages?
- Cells stained with fluorescent dyes
- Thick section of tissue scanned with laser beam
- Reflected by dye
- Multiple depths of tissue scanned to produce image
Adv :
- Thick or 3D (external) specimens
- External and internal structures observed
- High resolution
- Cytoskeleton can be observed
- High magnification
Disadv :
- Slow process
- Laser can cause photodamage
- Vacuum needed
- Length treatment process of sample
- Dead specimen
