module 2 - 2.3 more microscopy

Question 1

what are the main components of a light microscope?

Answer 1

they have 2 lenses which reduced chromatic abberation
typical magnification 1500x (theoretical resolution)

Question 2

why do light microscopes have 2 lenses?

Answer 2

to reduce chromatic abberation

Question 3

what are the disadvantages of light microscopy?

Answer 3

• increased magnification
• increased resolution NOT easily achieved (due to limit of resolution of 200nm/0.2μm

Question 4

what are the advantages of electron microscopy?

Answer 4

• electrons can be waves or particles, wave particle duality
• resolution from 0.5nm to 10nm
• electron microscopes allow cells ultrastructure to be seen

Question 5

what are the 2 types of electron microscopes?

Answer 5

transmission electron microscope (TEM)
scanning electron microscope (SEM)

Question 6

what are the components of a transmission electron microscope?

Answer 6

• sample embedded in resin, stained with heavy metal compounds & cut into thin sections in ultramicrotome
• specimen is ultra-thin section, between 70-350nm
• beams of electrons in vacuum are transmitted through sample
• image magnified and focused onto an imaging device

Question 7

what are 3 examples of imaging devices?

Answer 7

fluorescent screen, layer of photographic film, or sensor

Question 8

what are the components of a scanning electron microscope?

Answer 8

• produces image of sample by scanning surface with beam of electrons in a vacuum
• electrons interact with atoms
• covered with electrically conducting material

Question 9

what is an artefact?

Answer 9

visual anomalies during visual representation

Question 10

what is a mesosome?

Answer 10

they are invaginations in the plasma membrane of bacteria
produced by chemical fixation techniques

Question 11

what are some differences between light and electron microscopes?

Answer 11

LIGHT- inexpensive to buy and operate, small and portable, simple sample prep, no vacuum required, natural colour/ stain, living specimen
ELECTRON - expensive to buy and operate, large and installed, complex sample prep, vacuum required, black and white image, dead specimen

Question 12

what are some components of laser scanning confocal microscopes?

Answer 12

• optical microscope
• single focused light from a laser is moved across the specimen, causes fluorophores in the specimen to fluorescence
• higher optical resolution and contrast