Microscopes

Question 1

Resolution?

Answer 1

The minimum distance between 2 objects in which the can still be viewed as separate (distinguish between 2 separate points)

Question 2

Magnification:

Answer 2

Imagine size / object size
How many times larger the image is than the object

Question 3

Light microscope details

Answer 3

Res - 50-200nm

Mag - 1500x

Image - coloured + 2D

Typical specimen - alive/dead + thin

Qualities - easy 2 use, may req staining, small & portable & cheap

Question 4

TEM details

Answer 4

Res - 0.5nm
Mag - 500K
Image - black white + 2D
Typical specimen - dead thin
Qualities - expensive, req training, time consuming

Question 5

SEM details

Answer 5

Res - 3-10nm
Mag - 500K
Image - 3D Black & white
Typical specimen - thick/thin/dead
Qualities - heavy, expensive, training, not portable

Question 6

Laser Scanning confocal microscope details

Answer 6

Res - 200nm
Mag - 17820x
Image- 2D/3D coloured
Typical specimen - alive/dead/thick/thin
Qualities - heavy, training, expensive

Question 7

Steps for using graticules + stage micrometer etc (microscope stuff)

Answer 7

1. Use eyepiece graticule
2. Calibrate the graticule, using the stage micrometer: along the two scales and record the number of divisions per graticuke unit
3. Measure the diameter of the specimen or the nucleus etc in graticule units
4. Take repeat measurements (work out mean)
5. Use calibrate eye piece unit to calculate the real thing

Question 8

Advantages of staining (most common with light microscopy)

Answer 8

Differential staining: to identify different cellular components & types

Question 9

Slide prep for mounts
(Dry mount, wet mount, squash slides, smear slides)

Answer 9

Dry = when thin slices or whole specimens are viewed with just the cover slip placed on top e.g. plant tissue or hair
Wet = water added to the specimen before lowering the cover slip with a mounted needle to prevent air bubbles forming (2 view aquatic organisms)

Squash = wet mounts you push down on the cover slip to squash the sample to ensure you have a thin layer to enable light to pass through e.g, for root top samples to view chromosomes / mitosis

Smear = e.g. for blood cells: created using the edge of another slide to smear the sample across another one to create a smooth thin, even coated specimen, which you place a cover slip on top of.

Question 10

Common stains in differential staining

Answer 10

1. Crystal violet & methylene blue = 2 pos charged ones attracted to and stain neg charge ones
2. Nigrosin & congo red = neg charge so can’t enter cell as cytosol repels them: stained background forms so unstained cells stand out
3. Gram staining = using 2 diff stains to distinguish between bacteria e.g. gram pos and neg to not and to retain the stain (e..g gram positive retains it due to its thick peptidoglycan wall)

Question 11

Biological drawings checklist

Answer 11

• sharp pencil
• straight labels
• no arrowheads
• title to indicate the specimen
• no shading
  # scale / magnification
  No sketching
  Annotate only visible stuff
  Half a page
  Etc