lab quizzes

Question 1

Calculate the total magnification it a specimen is viewed under the high-dry objective (40x) objective

Answer 1

40 x 10 = 400x

Question 2

Define “working distance”

Answer 2

The distance between the specimen and objective lens

Question 3

How do you regulate the amount of light entering the condenser?

Answer 3

Iris diaphragm

Question 4

What controls on the microscope affect the amount of light reaching the ocular lens?

Answer 4

Iris diaphragm and rheostat (intensity)

Question 5

What are the 3 basic shapes of bacteria?

Answer 5

Bacillus, coccus, and spiral

Question 6

Why is it desirable for objectives to be parfocal?

Answer 6

If one lens is focused, all of the lenses will be in partial focus

Question 7

What is the function of the condenser and where is it located?

Answer 7

Has lenses to direct light to the specimen and is located below the stage

Question 8

What needs to be done if microbial cultures are spilled?

Answer 8

Soak paper tower w/ disinfectant and let sit for 20 mins before wiping

Question 9

How does true motility differ from brownian movement?

Answer 9

True motility: object moves from one point to another
Brownian movement: object shakes/ bounces bc of liquid molecules striking against it

Question 10

For illumination, you shone increase/decrease light w/ increasing power

Answer 10

Increase

Question 11

What are the steps of wet mount procedure

Answer 11

Add specimen suspended in liquid on slide, add coverslip, view w/ microscope

Question 12

Why do we need petroleum jelly for the hanging drop procedure w/ a depression slide

Answer 12

To seal the coverslip and prevent evaporation

Question 13

What is the purpose of adding methylcellulose to a slide

Answer 13

To slow down the microbes

Question 14

Mode of motility for amoeba proteus, euglena, and paramecium

Answer 14

Pseudopods, flagella, and cilia

Question 15

How do Cyanobacteria differ from algae

Answer 15

Cyanobacteria are prokaryotic cells w/o organelles

Question 16

Which of the following is likely to phagocytose a food particle: volvox (pond algae), HIV virus, E. coli, amoeba proteus, penicillium chrysogenum, S. Aureus

Answer 16

Amoeba proteus

Question 17

What do dinoflagellates in the genus Alexandria produce

Answer 17

Toxins

Question 18

What do dinoflagellates in the genus Alexandria produce

Answer 18

Toxins

Question 19

Define heterocyst

Answer 19

Specialized cell that fixes nitrogen

Question 20

Define cytosome

Answer 20

Mouth-like opening

Question 21

When inoculating, if you missed the opening and touched the outside of the tube instead, how should you proceed and why?

Answer 21

Flame the inoculating tool and tube because the tube may not have been fully sterilized

Question 22

What is the hyphal strand that is separated by a cell wall

Answer 22

septate hyphae

Question 23

Is yeast uni or multicellular

Answer 23

Unicellular

Question 24

Sabouraud dextrose agar (SDA) is used to culture fungi. This is a selective media that contains simple nutrients and has a low pH why?

Answer 24

To inhibit growth of other organisms

Question 25

What is the connect inoculating instrument: (1) agar slant, (2) agar deep, (3) lb broth, (4) lb agar Petri dish

Answer 25

(1) loop, (2) needle, (3) loop, (4) loop

Question 26

What method of sterilization is suitable for culture media containing fetal bone serum (FBs)? (FBs is heat-sensitive)

Answer 26

Cold sterilization w HEPA filters

Question 27

What are the phylum of these fungi: (1) Rhizopus stolonifera, (2) penicillium chrysogenum, (3) coprinus mushroom

Answer 27

(1) zygomycota, (2) ascomycota, (3) basidiomycota

Question 28

How does differential staining differ from simple staining

Answer 28

using 2 reagents instead of 1

Question 29

what are 2 methods to fix bacterial smears

Answer 29

1. heat fixing 2. chemical fixing using 95% methanol

Question 30

why is a thin layer of bacteria desired for a smear

Answer 30

otherwise, it will be too layered and crowded for viewing

Question 31

which inoculating instrument is used for a bacterial smear from liquid media

Answer 31

loop

Question 32

what is the value of using a negative stain technique to determine the cell morphology of bacterial cell

Answer 32

the cell remains colorless while the surrounding media is stained, we can view the cell's morphology without heat fixing

Question 33

what dye is used in the direct staining procedure

Answer 33

methylene blue

Question 34

what is the major difference in the outcome of the direct and indirect staining procedures

Answer 34

direct: dye stains the cells indirect: dye stains the surrounding media and cells are colorless

Question 35

define bacterial smear

Answer 35

thin film of bacteria on a slide

Question 36

when micrococcus luteus and e.coli are used for indirect staining: 1. what dye is used? 2. chromophore of the dye 3. shape of bacterial cells 4. color of bacterial cells

Answer 36

1. nigrosin 2. negative 3. coccus/spheres and bacillus/rods 4. colorless

Question 37

what is the colorless halo around some bacteria that were stained with both acidic and basic dyes

Answer 37

capusle

Question 38

what color is mycobacterium tuberculosis in acid-fast staining

Answer 38

red

Question 39

b.subtilis produces endospores if the conditions are no longer favorable for vegetative growth. what colors are expected for: 1. endospores 2. vegetative cells

Answer 39

1. green 2. red

Question 40

how do you remove liquid from ELISA microplate

Answer 40

tap on paper towel

Question 41

an old culture of 72 hours is used for endospore staining. the culture is gram-positive but the gram-stain shows pink-red rods. what is your conclusion?

Answer 41

since the culture is old, past 24 hours the cell walls begin to degrade. this prevents the CV-I complex from forming

Question 42

when conducting a gram-stain, you run out of safranin. can you still interpret your results?

Answer 42

yes because gram-pos will be purple and gram-neg will be colorless

Question 43

what is the difference between selective and differential media

Answer 43

selective: inhibits growth of other organisms and only allows one type of microbe to grow differential: allows all microbes to grow to show differences based on by-products

Question 44

what does ELISA stand for

Answer 44

enzyme-linked immunosorbent assay

Question 45

what is the chromogenic substrate necessary for result interpretation of ELISA

Answer 45

TMB

Question 46

two similarities between direct and indirect ELISA

Answer 46

1. positive result is blue 3. involves enzyme-linked antibodies

Question 47

two differences between direct and indirect ELISA

Answer 47

1. indirect is cheaper 2. direct detects antigens and indirect detects antibody

Question 48

what is tween-20 and what function does it play in ELISA

Answer 48

a chemical in the buffer which acts like a blocking agent

Question 49

if the washing step after the addition of the secondary antibody was omitted when performing indirect ELISA, what is the expected outcome for +/- controls and test wells? why?

Answer 49

pos control: blue neg control: blue test wells: blue there would be free-floating secondary antibodies in the well which bind to the substrate

Question 50

zombie virus is spreading on earth, there is a treatment but it must be distributed to infected people within 3 days of exposure. design a diagnostic assay that will confirm the presence of the virus.

Answer 50

direct elisa

Question 51

what is a media that is both selective and differential

Answer 51

MSA (mannitol salt agar)

Question 52

what is the desired outcome of the dilution streak method

Answer 52

to see individual colonies

Question 53

what causes metallic green appearance on EMB plate

Answer 53

precipitation of methylene blue from fermentation and production of acid

Question 54

two advantages of the dilution streak plate method

Answer 54

1. can see individual colonies 2. observing colony morphology

Question 55

two disadvantages of dilution streak plate method

Answer 55

1. can't count colonies 2. time consuming because of incubation

Question 56

what is the dilution if you mix 10mL bacterial culture int 10ml sterile LB broth

Answer 56

volume of sample/total volume = 10/20 = 1:2 dilution

Question 57

what does EMB agar inhibit

Answer 57

gram-positive

Question 58

what does PEA agar inhibit

Answer 58

gram-negative

Question 59

what makes the MSA plate selective and differential

Answer 59

selective: 7.5% NaCl differential: 1% mannitol

Question 60

how do you test to find out if a microbe is producing catalase? what do you add?

Answer 60

catalase test; add 3% H2O2

Question 61

in the presence of oxygen, what color does resazurin have?

Answer 61

pink

Question 62

why are palladium pellets added to the brewer jar with a gas pack

Answer 62

to catalyze reaction between hydrogen and oxygen to form water

Question 63

what is a microaerophile

Answer 63

uses limited oxygen and higher amounts can be inhibitory

Question 64

how do you fix a mixed tube of thioglycolate without using a fresh one

Answer 64

heat up the tube and wait for the layers to separate

Question 65

is an environment of .85% NaCl hyper or hypotonic for a microbe

Answer 65

hypertonic

Question 66

why is agar used as a solidifying agent instead of gelatin?

Answer 66

gelatin will get metabolized and agar will not

Question 67

what is the color of phenol red in neural ph and in presence of acid

Answer 67

neutral: red acidic: yellow

Question 68

what is acetoin

Answer 68

neutral end-product of fermentation

Question 69

what is amylase

Answer 69

exoenzyme that hydrolyzes starch into smaller carbohydrates

Question 70

what is the visual outcome of MRVP test if acetoin is present

Answer 70

MR test: yellow VP: red ring

Question 71

what is the ability of the lenses to reveal fine detail or distinguish between two points called

Answer 71

resolving power

Question 72

how is the inoculated agar plate incubated and why

Answer 72

upside down to prevent water from condensation to mix with the culture