2.1.2 - Slides and Micrographs

Question 1

What can you view using an optical microscope?

Answer 1

• living organisms e.g. amoeba
• smear preparations of human blood and cheek cells
• thin sections of animal, plant and fungal tissue e.g. bone, muscle, leaf, root or fungal hyphae

Question 2

How can you observe living organisms with a light microscope?

Answer 2

adjusting the iris diaphragm to reduce the illumination of the specimen

Question 3

What are stains?

Answer 3

coloured chemicals that bind to molecules in or on the specimen, making it easy to see

Question 4

What is differential staining?

Answer 4

where some stains bind to specific cell structures. staining each structure differently so they can be easily identified within a single preparation

Question 5

Name some stains used in slides

Answer 5

• acetic orecin: binds to DNA strands and stains chromosomes dark red
• eosin: stains cytoplasm; Sudan red stains lipids
• iodine in potassium iodine solution: stains cellulose in plant cell walls yellow, and starch granules blue/black (violet under microscope)

Question 6

How are slides made?

Answer 6

1. specimens are dehydrated
2. dried specimens embedded in wax to prevent distortion during slicing
3. thin slices (sections) made - these are stained and mounted in a special chemical to preserve them

Question 7

How do you find the actual size of structures?

Answer 7

• measure the widest part of the specimen on the photomicrograph in mm
• convert that measurement to um by multiplying by 1000
• divide this figure by the magnification
  this tells you the actual thickness of the specimen at this point