2.1.2. slides & photomicrographs

Question 1

what specimens can you view with an optical microscope (light)

Answer 1

• living organisms
• smear preparations of human blood/cheek cells
• thin sections of animal, plant & fungal tissue

Question 2

ways specimens can be viewed without a stain

Answer 2

• light interference
• dark background which illuminates specimen

Question 3

what are stains

Answer 3

chemicals that bind to molecules in/on specimen, making it easier to see

Question 4

describe differential staining

Answer 4

some stains bind to specific cell structures & stain each differently = structures can be identified with a single preparation

Question 5

give 3 examples of stains

Answer 5

• acetic orcein = binds to DNA & stains chromosomes dark red
• eosin = stains cytoplasm
  -> sudan red stains lipids
• iodine (potassium iodide soluton) stains cellulose in plant cell walls yellow & starch granules blue/black

Question 6

3 ways of observing specimens

Answer 6

• dehydrating
• embedding in wax to prevent distortion during slicing
• special instrument to make very thin slices (sections) & stained/mounted in chemical to preserve

Question 7

drawing slides

Answer 7

1. sharp HB pencil
2. title to explain drawing & magnification used
3. indicate scale
4. clear unbroken lines
5. do not shade
6. label - ruler & non-overlapping