Lecture 3

Question 1

Why is staining important

Answer 1

improves CONTRAST between different cells/features

Question 2

resolution

Answer 2

The ability to distinguish between two adjacent objects as distinct and separate

Question 3

resolution is a function of..

Answer 3

the physical properties of light

Question 4

resolution is determined by..

Answer 4

the wavelength of light used and numerical aperture of lens

Question 5

resolution is _________________ to wavelength

Answer 5

inversely proportional

Question 6

shorter wave length =

Answer 6

better resolution

Question 7

Limit of resolution for light microscope is about…

Answer 7

o.2 um

Question 8

Compound light microscopes use….. to illuminate cells

Answer 8

visible light

Question 9

4 types of light microscopy

Answer 9

• bright-field
• phase contrast
• dark-field
• fluorescence

Question 10

bright field microscopy

Answer 10

specimens are visualized because of differences in contrast (density) between specimen and surroundings

Question 11

total magnification =

Answer 11

objective magnification x ocular magnification

Question 12

Maximum useful magnification is…

Answer 12

~2000x

Question 13

Phase-Contrast Microscroscopy was invented in 1936 by…

Answer 13

Frits Zernike

Question 14

Phase Contrast Microscopy

Answer 14

• amplifies differences in the refractive index of cell and surroundings;
• improves contrast without use of stain
• allows for visualization of live samples
• dark cells on a light background

Question 15

dark field microscopy

Answer 15

light reaches the specimen from the sides

• good for observing motility
• appears light on a dark background

Question 16

fluorescence microscopy

Answer 16

used to visualize specimens that fluoresce

• may fluoresce naturally of after staining
• widely used for enumerating bacteria

Question 17

differential interference contrast microscopy

Answer 17

uses a polarizer to create two distinct beams of polarized light
-gives structures such as endospores, vacuoles, and granules a 3D appearance

Question 18

atomic force microscopy

Answer 18

-a tiny styles is placed close to a specimen and it measures weak repulsive forces between it and the specimen

Question 19

confocal scanning laser microscopy

Answer 19

-computerized fluorescence microscope coupled with a laser source to generate a 3D image

Question 20

electron microscopy

Answer 20

electron microscopes use electrons instead of photons to image cells and structures

Question 21

transmission electron microscopy

Answer 21

operates in a vacuum and is used to examine cells and cell structure at very high magnification and resolution

• visualization at a molecular level
• specimen must be very thin and stained

Question 22

scanning electron microscopy

Answer 22

for observing external features

-specimen is coated with a thin film of heavy metal and an electron beam scans object to form image

Question 23

morphology

Answer 23

cell shape

Question 24

coccus

Answer 24

spherical

Question 25

rod

Answer 25

cylindrical

Question 26

spirillum

Answer 26

spiral

Question 27

cells with unusual shapes

Answer 27

spirochete, appendages bacteria, and filamentous bacteria

Question 28

Morphology typically ___________ physiology, ecology, phylogeny, etc. of a prokaryotic cell

Answer 28

does NOT predict

Question 29

May be _________ _______ involved in setting the morphology

Answer 29

selective forces