Lab test 1

Question 1

light microscope

Answer 1

• described as compound microscope
• b/c it has a optical system that uses two lenses(objective lens and ocular lens)
• light to magnify(enlarge) the object

Question 2

object

Answer 2

• the actual specimen

- the image is an enlargement(magnification) of the object

Question 3

the letter e is upside down and backwards

Answer 3

the letter e is upside down and backwards

Question 4

magnification

Answer 4

-enlargement of the object

Question 5

resolving power(resolution)

Answer 5

-the power of the optical system the microscope to distinguish between two separate objects a certain distance apart in order to discern fine detail or structure(image not blurred)

Question 6

limit of resolution

Answer 6

the distance between two objects at which it first becomes impossible to resolve them as separate
-the object cannot be resolved anymore by the light microscope

Question 7

microscopists

Answer 7

always start with the 4x or 10x objective(10x objective if microscope does not have 4x objective.) b/c the 4x objective is the scanning lens, which allows one to view the entire field in order to locate the specimen

Question 8

brightness control(rheostat or voltage regulator)

Answer 8

-functions to regulate the intensity of light from the bulb onto the specimen

Question 9

iris diaphragm

Answer 9

-functions to control the amount of light entering the condenser lends in order to create contrast(a dark back round)

Question 10

working distance(focal length)

Answer 10

the distance between the objective lens and the slide(specimen) when the specimen is in focus. the 4x objective has the longest working distance, while the 100x has the shortest working distance

Question 11

parfocal

Answer 11

the lenses of the microscope are adjusted so that the specimen remains somewhat in focus when switching from a low power to a high power objective lens
-the microscope requires little adjustment with the coarse or fine adjustment knobs

Question 12

refraction

Answer 12

refers to the bending of light rays by the convex objective and oculars lenses of the microscope which serves to magnify the specimen

Question 13

simple stain

Answer 13

-it is important to make the smear thin so that the cells will be separated and clearly observable

Question 14

heat fix

Answer 14

• to kill the cells

- to ensure that the cells adhere to the microscope slide

Question 15

methylene blue

Answer 15

a positive basic stain that attaches to negative, acidic cell parts

Question 16

cultue tube

Answer 16

-should be held at a 45 degree angle so that microorganisms in the air cannot enter the mouth of tube and contaminate it

Question 17

morphology

Answer 17

refers to size and shape of cells

-groor groupings of cells

Question 18

growth arrangement

Answer 18

• refers to patterns of bacterial cell divisions or grouping of cells
• ex: diplococci(paired cells)
• streptobacilli(chains of 4 or more rod shaped cells)

Question 19

streptobacilli

bacillus subtilus

Answer 19

chains of 4 or more large rod shaped cells(streptobacilli)

Question 20

streptococcus pneumoniae

diplococci

Answer 20

pair of spherical shaped cells

-diplococci

Question 21

e coli

Answer 21

small

single rod shaped cells

Question 22

staphylococcus aureus

staphylococci

Answer 22

grape-like clusters of spherical shaped cells(staphyloccoi)

Question 23

streptococus pyogenes

streptococci

Answer 23

chains of 4 or more spherical shaped cells(streptococci)

Question 24

gram stain

Answer 24

-differential staining technique because it uses two different colored dyes, primary stain and a counterstain, in order to distinguish between gram-positive and gram negative cell wall structure.

Question 25

primary stain

Answer 25

Crystal violet dye

Question 26

mordant

Answer 26

grams iodine

Question 27

decolorizer

Answer 27

ethyl alcohol(95%)

Question 28

counterstain

Answer 28

safranin red dye

Question 29

mordant

Answer 29

• a chemical that fixes/ retains the crystal violet dye in the cell wall of both gram-positive and gram-negative bacteria.
• crystal violet-iodine complex becomes trapped in the peptidoglycan layer of the cell wall

Question 30

gram positive cell wall

Answer 30

one layer: thick peptidoglycan layer bound by teichoic acids

Question 31

gram negative cell wall

Answer 31

two layers:
1-inner layer thin peptidoglycan layer
2-outer membrane layer, phospholipid bilayer, containing lipoplysaccharides
-lipopolysaccharide components contain two important parts, the O-antigen and the lipid A endotoxin

Question 32

alcohol

Answer 32

disrupts the outer lipid layer of the gram negative cell wall and removes the crystal violet stain

Question 33

gram stain

Answer 33

if the gram stain procedure was stopped after crystal violet dye was applied, but prior to decolorization, both gram negative and gram-positive bacterial cels would appear purple(violet)

Question 34

gram stain

Answer 34

if the gram stain procedure was stopped after decolorization, gram negative bacterial cells would appear colorless, while gram positive bacterial cells would appear purple(violet)

Question 35

gram stain

Answer 35

if at the end of the gram stain procedure both gram positive and gram negative bacterial cells appeared reddish pink the most likely explanation would be:

a) too much decolorized was used and was left on the slide for too long a period of time
b) the mordant(gram iodine) step was skipped

if the bacteria appear both purple and pink(gram variable), it is because the cultures are too old

Question 36

bacillus subtilus

Answer 36

the organism(bacterium) found to be gram positive(purple)

Question 37

e coli

Answer 37

the organism(bacterium) found to be gram negative(reddish-pink)

Question 38

morphology of gram positive organism(bacterium)

Answer 38

• bacillus subtilus
• large, rod shaped cell in chains
• streptobacilli

Question 39

morphology of gram negative organism(bacterium)

Answer 39

• e coli

- small single rod shaped cells