microscopy

Question 1

how does a light microscope work?

Answer 1

light from a light source underneath the specimen passes through the specimen

Question 2

what is the resolution of an light microscope?

Answer 2

200nm

Question 3

what is the magnification of an light microscope?

Answer 3

x1500

Question 4

what are the strengths of light microscopes?

Answer 4

• colour image
• uses live specimens

Question 5

what are the weaknesses of light microscopes?

Answer 5

• poor resolution
• 2D image

Question 6

what do light microscopes allow us to see?

Answer 6

whole cells/tissues

Question 7

why is resolution of a light microscope limited?

Answer 7

light has a larger wavelength

Question 8

how does a transmission electron microscope work?

Answer 8

electrons are transmitted through a specimen and denser parts of the specimen absorb more electrons, becoming darker

Question 9

what is the resolution of a TEM?

Answer 9

0.5nm

Question 10

what is the magnification of a TEM?

Answer 10

x1,000,000

Question 11

what are the strengths of TEMs?

Answer 11

• good resolution

Question 12

what are the weaknesses of TEMs?

Answer 12

• black and white image
• 2D image
• specimens must be dead

Question 13

what do TEMs allow us to see?

Answer 13

small organelles

Question 14

how do scanning electron microscopes work?

Answer 14

electron beam is scanned across the specimen surface and electrons bounce off, gathering in a cathode ray tube

Question 15

what is the resolution of SEMs?

Answer 15

2nm

Question 16

what is the magnification of SEMs?

Answer 16

x500,000

Question 17

what are the strengths of SEMs?

Answer 17

3D image

Question 18

what are the weaknesses of SEMs?

Answer 18

• black and white image
• specimen must be dead

Question 19

how do laser scanning confocal microscopes work?

Answer 19

• laser beam focuses on a small area on a sample surface
• fluorophores in the sample emit photons
• photomultiplier tube amplifies signal onto a detector
• image is produced in pixels

Question 20

what is the magnification calculation?

Answer 20

mag = image / actual

Question 21

what does magnification mean?

Answer 21

how many times larger the image is compared to the object

Question 22

what does resolution mean?

Answer 22

the ability to distinguish between two points

Question 23

which lens is the objective?

Answer 23

near to specimen

Question 24

which lens is the eyepiece?

Answer 24

used to view specimen

Question 25

why are there two lenses on a microscope?

Answer 25

improves magnification

Question 26

what is a dry mount?

Answer 26

a solid specimen viewed whole or sectioned on a slide under a cover slip

Question 27

what is a wet mount?

Answer 27

specimen suspended in liquid with a cover slip placed at an angle

Question 28

how is a squash slide prepared?

Answer 28

- wet mount prepared - lens tissue used to press down cover slip - used for soft samples

Question 29

how is a smear side prepared?

Answer 29

- edge of slide used to smear a sample to create a thin coating - cover slip over top

Question 30

why should specimens on a slide be thin?

Answer 30

avoid air bubbles

Question 31

why is a stain sometimes used?

Answer 31

increase contrast to improve visibility

Question 32

what is differential staining?

Answer 32

distinguishes between two organisms/organelles - positive dye attracts negative cytoplasm materials

Question 33

what is a gram stain?

Answer 33

- separate pos and neg bacteria - crystal violet applied to slide - iodine added - alcohol washes away unbound stain - gram pos appears blue - gram neg doesnt retain stain - counterstain added to stain gram neg

Question 34

what is the acid fast technique?

Answer 34

- differentiates mycobacterium - lipid solvent carries a dye into cells - mycobacterium not affected by acid alcohol cell wash absorbs dye

Question 35

how are mm converted to micrometres?

Answer 35

x1000

Question 36

how are micrometres converted to nm?

Answer 36

x1000

Question 37

how is the actual length of an image calculated using a stage micrometer?

Answer 37

- line up eyepiece graticule with stage micrometer - count how many graticule divisions are in 100 micrometres - number of divisions / 100 = 1 division