microscopy

Question 1

how does an optical microscope work?

Answer 1

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

Question 2

what is the resolution of an optical microscope?

Answer 2

200nm

Question 3

what is the magnification of an optical microscope?

Answer 3

x1500

Question 4

what are the strengths of optical microscopes?

Answer 4

• colour image
• using live specimens

Question 5

what are the weaknesses of optical microscopes?

Answer 5

• poor resolution
• 2D image

Question 6

what do optical microscopes allow us to see?

Answer 6

whole cells/tissues

Question 7

how deos a transmission electron microscope work?

Answer 7

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

Question 8

what is the resolution of a TEM?

Answer 8

0.5nm

Question 9

what is the magnification of a TEM?

Answer 9

x1,000,000

Question 10

what are the strengths of TEMs?

Answer 10

• good resolution

Question 11

what are the weaknesses of TEMs?

Answer 11

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

Question 12

what do TEMs allow us to see?

Answer 12

small organelles

Question 13

how do scanning electron microscopes work?

Answer 13

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

Question 14

what is the resolution of SEMs?

Answer 14

2nm

Question 15

what is the magnification of SEMs?

Answer 15

x500,000

Question 16

what are the strengths of SEMs?

Answer 16

• 3D image

Question 17

what are the weaknesses of SEMs?

Answer 17

• black and white image
• specimen must be dead

Question 17

what is the magnification calculation?

Answer 17

mag = image / actual

Question 18

what does magnification mean?

Answer 18

amount of times the image has been expanded than the object

Question 19

what does resolution mean?

Answer 19

the ability to distinguish between two objects

Question 20

which lens is the objective?

Answer 20

near to specimen

Question 21

which lens is the eyepiece?

Answer 21

used to view specimen

Question 22

why are there two lenses on a microscope?

Answer 22

• improves magnification
• reduces chromatic abreviation (diff colours traveling at diff speeds)

Question 23

why is resolution limited for optical microscopes?

Answer 23

light has a larger wavelength

Question 24

what is a dry mount?

Answer 24

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

Question 25

what is a wet mount?

Answer 25

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

Question 26

how is a squash slide prepared?

Answer 26

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

Question 27

how is a smear slide prepared?

Answer 27

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

Question 28

why should speciens on a slide be thin?

Answer 28

avoid air bubbles

Question 29

why is a stain sometimes used?

Answer 29

increase contrast to improve visibility

Question 30

what is differential staining?

Answer 30

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

Question 31

what is a gram stain?

Answer 31

* separates pos/neg bacteria * crystal violet is applied to slide * iodine apllied to fix dye * washed with alcohol

Question 32

what is the acid fast technique?

Answer 32

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

Question 33

how are mm converted into micrometres?

Answer 33

x1000

Question 34

how are micrometres converted to nm?

Answer 34

x1000

Question 35

how do you identify what is stained when using crystal violet and methylene blue?

Answer 35

negative organelles attract positive stain

Question 36

how do you identify what is stained when using nigrosin or methylene blue?

Answer 36

positive organelles attract negative stain

Question 37

how does a laser scanning confocal microscope work?

Answer 37

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

Question 38

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

Answer 38

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