Microscopy

Question 1

What is resolution?

Answer 1

The ability to be able to distinguish two separate points in an image.

Question 2

What is magnification?

Answer 2

How large the image (under a microscope) is compared to actual size.

Question 3

What are the advantages and disadvantages of an optical (light) microscope?

Answer 3

Advantages:

• Cheap

• Easy to use

Disadvantages:

• Low magnification

• Low resolving power

Question 4

What are the advantages and disadvantages of scanning electron microscopes (SEMs)?

Answer 4

Advantages:

• Allows 3D images

Disadvantages:

• Lower resolution and lower magnification than TEMs

Question 5

What are the advantages and disadvantages of transmission electron microscopes (TEMs?

Answer 5

Advantages:

• Can see internal structures

• High magnification and resolving power

Disadvantages:

• Expensive

• Hard to operate

Question 6

What is differential staining?

Answer 6

Using multiple stains to create contrast in the image, as the stains bind to different organelles.

Question 7

What are the different colours created by stains, and what organelle do they affect?

Answer 7

• Acetic orecin - binds to DNA and stains chromosomes dark red

• Eosin - stains cytoplasm dark red or pink

• Iodine - stains starch blue-black (appears violet under the microscope)

• Iodine in potassium iodide solution - stains cellulose yellow

• Haematoxylin - stains RNA/DNA a purple/blue colour

• Methylene blue - all purpose stain, often used to stain DNA blue