Chapter 3.2 Microscopy

Question 1

Dimensions of macroscopic organisms are given in terms of

Answer 1

meters (m) and centimeters (cm)

Question 2

Dimensions of microscopic organisms are measured from

Answer 2

millimeters (mm) to micrometers (μm) to nanometers (nm)

Question 3

Three properties on compound/light microscope

Answer 3

-Magnification
-Resolution
-Contrast

Question 4

Magnification

Answer 4

-Glass sphere can make objects appear larger than they are
-Results from complex interaction between visible light waves and curvature of a lens

Question 5

Magnifying power

Answer 5

Calculated by multiplying the power of the ocular lens by the power of the objective lens

Question 6

Resolution

Answer 6

capacity of an optical system to distinguish or separate two adjacent objects or points from one another

Question 7

Resolving power

Answer 7

-The limit up to which two small objects are still seen as separate entities
-Shorter wavelengths have increased power

Question 8

Contrast

Answer 8

the difference in light intensity between the image and the adjacent background relative to the overall background intensity

Question 9

Refractive index

Answer 9

The degree of contrast (the bending of light as it passes from one medium to another)

Question 10

Four types of light microscopes

Answer 10

-Bright-field
-Dark-field
-Phase-contrast
-Interference

Question 11

Bright-field microscope

Answer 11

white light transmitted through sample (simplest of microscopes)

Question 12

Dark-field microscope

Answer 12

Used to enhance contrast in unstained samples causing them to appear bright against a dark background

Question 13

Phase-contrast microscope

Answer 13

used to enhance contrast in clear or transparent samples

Question 14

Inference microscope

Answer 14

Used to visualize surface features of sample

Question 15

Fluorescence microscope

Answer 15

Uses ultraviolet radiation as the illuminating scource

Question 16

Confocal microscope

Answer 16

Uses a laser beam as the illuminating source

Question 17

Wet Mounts

Answer 17

-provide a true assessment of size,shape, arrangement, color and motility of cells
-Consists of a drop or two of culture placed on a slide overlaid with a cover slip
-Dry out quickly under microscope light/ for short term observation

Question 18

Hanging drop Mounts

Answer 18

-provide a true assessment of size,shape, arrangement, color and motility of cells
-Prepared with concave slide, Vaseline and a cover slip
-Complex technique but allows for longer term observation and more reliable observation of motility.

Question 19

Fixed smear technique

Answer 19

-Smear thin film made from a liquid suspension of cells on slide
-allow to air dry
-Heat or chemical fix kills the cells, secures specimen to slide, preserves cellular components in a natural state w/ minimal distortion

Question 20

Staining fixed smears

Answer 20

Provides contrast with basic/cationic (positive) or Acidic/anionic (negetive) dyes

Question 21

Basic (cationic)

Answer 21

Have positive charge, attracted to acidic, negatively charged components on bacterial cell walls

Question 22

Acidic (anionic)

Answer 22

Have negative charge, repelled by acidic, negatively charged components on bacterial cell wall

Question 23

Positive stain

Answer 23

-attracted to negatively charged cell walls
-Sticks to the cell and gives it color

Question 24

Negative stain

Answer 24

-Repelled by negatively charged cell walls
-Produces dark background around cells

Question 24

Types of stains

Answer 24

-Simple stains
-Differential stains
-Special stains

Question 24

Simple stains

Answer 24

-crystal violet, safranin and methylene
-Used to determine bacterial species, morphology and arrangement (single, chains, clusters) but no additional info

Question 25

Differential stains

Answer 25

-Gram stain
-Acid-fast stain
-Endospore stain

Question 26

Gram Stain

Answer 26

-Universal diagnostic staining technique for bacteria
-Permits ready differentiation of major categories based on the color of cells
-Gram positive stains purple
-Gram neg stains pink

Question 27

Acid-fastness

Answer 27

Physical property that gives bacterium ability to resist de-colorization from acids during staining procedures

Question 28

Acid-fast stain

Answer 28

-Differentiates acid-fast bacteria from non acid-fast bacteria
-Acid fast bacteria stain red/pink
-Non acid-fast stain blue
-Detects agents of tuberculosis and leprosy

Question 29

Endospore stain

Answer 29

-Distinguishes vegetative (active) cells from dormant endospores
-Endospores are green
-Vegetative cells are red

Question 30

Special stains

Answer 30

-Capsule stain
-Flagellar stain

Question 31

Capsule stain

Answer 31

-Special stain
-For viewing capsule
-negative staining with India ink or special positive stains

Question 32

Flagellar stain

Answer 32

-Reveals flagella
-deposits coating on outside of filament and then stained