Types of Microscopes

Question 1

What is the use of a light microscope?

Answer 1

• let us see structures like nuclei and mitochondria

Question 2

What are the advantages of a light microscope?

Answer 2

• living specimen
• colour
• easy to make specimen
• cheap and easy to transport
• simple stains

Question 3

What are the disadvantages of a light microscope?

Answer 3

• 200nm resolution limit

- 1500x magnification limit

Question 4

What is the use of a Transmission Electron Microscope (TEM)?

Answer 4

• electrons transmitted through specimen
• specimen stained with radioactive stain
• makes 2D image of inside the cell

Question 5

What are the advantages of a TEM?

Answer 5

• 0.2nm resolution and 500,000 x magnification limit

- see internal structures

Question 6

What are the disadvantages of a TEM?

Answer 6

• dead samples only
• need vacuum
• radioactive stain
• expensive
• 2D images are black and white

Question 7

What is the use of a Scanning Electron Microscope (SEM)?

Answer 7

• electrons beamed onto surface
• makes 3D image of outside the cell
• up to 200000 x magnification

Question 8

What are the advantages of a SEM?

Answer 8

• 3D images
• colour added after
• higher resolution and magnification than a light microscope but less than a TEM

Question 9

What are the disadvantages of a SEM?

Answer 9

• dead samples only
• can’t see internal structures
• expensive

Question 10

What is the use of a confocal microscope?

Answer 10

• use laser beams of light to illuminate chemical stains within specimen
• then turns it fluorescent

Question 11

What are the advantages of a confocal microscope?

Answer 11

• larger resolution than light microscope

Question 12

What are the disadvantages of a confocal microscope?

Answer 12

• expensive

Question 13

What is gfp and how can we use it?

Answer 13

• engineer bacteria or viruses with fluorescent tags and view them using microscopy (green fluorescent protein gene) gfp from jelly fish
• locating cancer cells with gfp
• see how viruses enter target cells
• see interaction between different proteins inside the cell

Question 14

What are the problems with microscopes?

Answer 14

• specimens not alive so hard to know how a mechanism happens in real time
• can’t see whole story in 1 still image
• artefacts: when cell structure becomes distorted during sample process, present in electron micrograph

Question 15

Whats the difference between a light and electron microscope?

Answer 15

• electron microscopes using electrons not light

- has shorter wavelength

Question 16

Explain why artefacts are more likely to be produced when preparing sample for electron microscopy than for light

Answer 16

• more sample preparation
• leads to more damage to specimen
• damage results in artefact

Question 17

What does fluorescent mean?

Answer 17

• answers emission of light that’s been absorbed

Question 18

Why are lasers used to provide illumination?

Answer 18

• increase in intensity of light

Question 19

What is the use of pinhole aperture in confocal microscopy?

Answer 19

• scattered light from outside focal plane is eliminated
• reduces blurring
• increases resolution

Question 20

Why can’t confocal microscopy be used for deep tissue imaging?

Answer 20

• light penetration is limited