2.1.2- Slides And Photomicrographs

Question 1

What are ‘stains’?

Answer 1

They’re coloured chemicals that bind to molecules in or on the specimen, making the specimen easier to see.

Question 2

Explain what differential staining is.

Answer 2

When some stains bind to specific cellular structures to stain each structure differently and can be identified within a single preparation.

Question 3

Describe four examples of how differential staining can be utilised.

Answer 3

~Eosin stains cytoplasm.
~Sudan red stains lipids.
~Acetic Orcein binds to DNA and dark red stains chromosomes.
~Iodine in Potassium Iodine solution stains cellulose yellow and starch granules blue or black.

Question 4

Explain how experts make ‘prepared and permanently fixes slides’.

Answer 4

• dehydrating the specimens
• embedding them in wax- prevents distortion during slicing
• make sections (v thin slices) that are stained and mounted in a special preserving chemical

Question 5

What is the equation for linking actual size of a structure (A), the image size of the photomicrograph (I) and magnification (M)?

Answer 5

Magnification= Image Size/ Actual Size

M=I/A

Question 6

List the types of specimen that can be viewed using optical microscopes.

Answer 6

• Living Organisms- eg. Amoeba/ Paramecium
• Smears preparations of human blood and cheek cells
• Thin plant/ animal/ fungal tissue sections