3 - Microscopy

Question 1

The ability of the lenses to distinguish fine detail and structures is called
a. illumination
b. magnification
c. refractive index
d. resolution

Answer 1

d. resolution

Question 2

Which microscope would you choose to view the cellular contents of a microbe in its natural state?
a. compound light microscope
b. phase-contrast microscope
c. darkfield microscope
d. electron microscope

Answer 2

b. phase-contrast microscope

Question 3

Which microscope uses an ultraviolet light source?

Answer 3

fluorescence microscope

Question 4

How does a compound light work?

Answer 4

uses lenses and visible light to magnify

Question 5

What is another name for the compound light microscope?

Answer 5

Brightfield microscopy

Question 6

What is the total magnification of a compound light microscope?

Answer 6

2000x max magnification

Question 7

How is magnification calculated on compound light microscope?

Answer 7

objective lens x magnification of ocular lens

Question 8

What is resolution?

Answer 8

ability to distinguish between two points

Question 9

What is the path of light of a light microscope?

Answer 9

1. illuminator
2. condenser lenses
3. specimen
4. objective lenses
5. body tube (prism)
6. ocular lens
7. line of vision

Question 10

Ocular lens

Answer 10

eyepiece: remagnifies the image formed by the objective lens

Question 11

Body tube

Answer 11

transmits the image from the objective lens to the ocular lens

Question 12

Objective lens

Answer 12

primary lenses that magnify the specimen

Question 13

Stage

Answer 13

holds the microscope slide in position

Question 14

Condenser

Answer 14

focuses light through the specimen

Question 15

Iris diaphragm

Answer 15

controls the amount of light entering the condenser (like a door)

Question 16

Illuminator

Answer 16

the light source

Question 17

Darkfield microscope

Answer 17

visualizes microbes that are invisible in normal light or can’t be stained/ it blocks light so that the specimen is light and the background is dark

Question 18

Phase-contrast microscope

Answer 18

details of internal structures in microbes; light wave phases:peaks and valley - inside cell clearer

Question 19

Fluorescence microscope

Answer 19

uses UV light, specimen may naturally fluoresce or is stained with fluorescent dyes

Question 20

Confocal microscope

Answer 20

constructs 3D images using a computer - it takes scan slices of an image that a computer puts together

Question 21

What is electron microscopy?

Answer 21

objects smaller than 0.2um - uses beams of electrons instead of light and electromagnets instead of glass lenses

Question 22

Transmission electron microscope

Answer 22

1. beams pass through specimen
2. 10,000-100,000x mag.
3. INTERNAL structure
4. distortion

Question 23

Scanning electron microscope

Answer 23

1. gives 3D views
2. 1,000-10,000x mag.
3. bema is directed to SURFACE of specimen

Question 24

What is a smear?

Answer 24

microbe attached to slide

Question 25

Why do we fix bacteria?

Answer 25

keeps microbe from being washed off slide with stain

Question 26

Why are basic dyes used?

Answer 26

cell surface has a slightly negative charge and positive ion of dye adheres to surface

Question 27

Simple stain

Answer 27

single basic dye

Question 28

Differential stain

Answer 28

distinguish between bacteria - multiple dyes that react differently with different bacteria

Question 29

Gram stain steps (4):

Answer 29

1. crystal violet 2. iodine (mordant) 3. alcohol (decolorize) 4. safranin (counterstain)

Question 30

Why would we do an acid-fast stain?

Answer 30

mycobacterium (TB/leprosy) - binds to bacteria with waxy material (mycolic acid) in cell walls

Question 31

List the steps of the acid-fast stain:

Answer 31

1. stained with red dye carbolfuchsin (simple stain) 2. washed and covered with alcohol (removes red from non acid-fast bacteria) 3. stained with methylene blue

Question 32

What color will acid fast vs. non-acid fast bacteria be?

Answer 32

1. acid-fast= red (carbolfuchsin is soluble in lipids of cell wall) 2. non-acid-fast= blue

Question 33

Negative stain

Answer 33

for microbes with capsules - microbe is mixed with color particles - contrast b/w microbe and colored background

Question 34

Endospore stain

Answer 34

malachite green stains endospores within pink stained cells

Question 35

Flagella stain

Answer 35

structures of cell movement/carbolfuchsin

Question 36

Primary stain

Answer 36

color to all cells