3: Microscopy

Question 1

What are the two kinds of microscopes?

Answer 1

Light Microscopes and Electron Microscopes

Question 2

Explain a Compound Light Microscope

Answer 2

Uses two lenses to observe
The objective lens in closest to the specimen
The ocular lens is closest to the eye
Multiple two magnifications

Question 3

Explain how an Electron Microscope works

Answer 3

Uses beams of electrons
Shorter waves than light waves
Much better resolution

Question 4

Explain Transmission Light Microscope

Answer 4

Electron cut into thin sections to view internal structure
Stain is used to contrast

Question 5

Explain Scanning Electron Microscopy

Answer 5

Specimen is coated with heavy metal
Can only view surface

Question 6

Explain Scanning Tunneling Microscopy

Answer 6

Most powerful electron microscope
Uses needle to view topography of specimen

Question 7

Difference between +’ve and -‘ve stains (chromophores)

Answer 7

+‘ve sticks to bacteria
-‘ve stains background

Question 8

What is a simple stain

Answer 8

Single colour dye
+‘ve so sticks to organisms

Question 9

What is a differential stain

Answer 9

Reacts differently to different bacteria
Gives more detail

Question 10

What is the gram stain used for

Answer 10

To determine if bacterium is gram +’ve or -‘ve

Question 11

Explain what an Acid Fast Stain is

Answer 11

Pink dye sticks to hydrophobic bacterium such as mycolic acid
everything else is stained purple

Question 12

What is a capsule stain

Answer 12

Background is dyed with -‘ve
Cell is dyed with +’ve leaving a capsule looking like a clear halo

Question 13

What is an Endospore Stain

Answer 13

Special type of stain is used since normal ones cannot penetrate endospores

Question 14

What is a Flagella Stain

Answer 14

A stain and then mordant increase the thickness of flagella so they are viewable