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Microbiology Lab > Exam 1 Objectives > Flashcards

Exam 1 Objectives Flashcards

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Biology 101 flashcards
1
Q

what is a simple microscope

A

it is used to produce an enlarged image of an object placed within its focal length; single lens; no condenser

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2
Q

what is a compound microscope

A

3 to 5 lenses; better magnifying power; has condenser lens; illuminator is the source of light; used for detail and studying structure

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3
Q

what is the power of the objective and ocular lenses

A 
ocular=10x
oil immersion=100x
scanning=4x
objective=10x
objective=40x
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4
Q

explain the use of immersion oil and how it allows the microscopist to obtain greater resolution

A

placing a drop of oil with some refractive index as glass between the cover slip and objective lens eliminates two refractive surfaces, can achieve greater magnification while preserving resolution

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5
Q

describe resolving power

A

the actual measurement f how far apart two points must be for microscope to view them as separate

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6
Q

describe numerical aperture

A

measure of a lens ability to capture light coming in from specimen and used to make an image

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7
Q

what does the blue light equal

A

shorter wavelength

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8
Q

explain why a blue filter is used beneath the condenser of our microscopes

A

it increases contrast between a specimen and its background, also has better higher resolution

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9
Q

describe the change in working distance as magnification increases

A

as magnification increases, working distance decreases

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10
Q

what does parfocal mean

A

having corresponding focal points in all the same plane

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11
Q

what is the advantage to the microscopist parfocally

A

the advantage is it allows more accurate focusing at maximum focal length and then zooming back to a shorter focal length to compose the image

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12
Q

describe the change in the size of the field of view as magnification increases

A

as magnification increases, size of field decreases

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13
Q

what is the field of view

A

how much of your subject you see through the lens

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14
Q

how does the orientation of the image change under the microscope compared to the orientation of slide

A

the optics of the microscope inverts the image(turns it upside)

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15
Q

compare the size of human blood cells with yeast cells and typical bacilli and cocci

A

human blood cells= 12um
yeast= 3-4 um
bacilli= .2-2 um
cocci= 1-2 um

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16
Q

what is meant by depth of field

A

distance through which you can move the specimen and still have it remain in focus

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17
Q

what is a pure culture

A

lab culture with one species of organism

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18
Q

what is a mixed culture

A

lab culture with two species of organism

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19
Q

what is aseptic

A

without contamination of culture, the sterile medium or the surroundings

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20
Q

what is sterile

A

killing all forms of microbe life

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21
Q

what is contamination

A

the unintended introduction of microbes in areas or on surfaces they should not be

22
Q

what is broth

A

used to grow stock culture

23
Q

what is a slant

A

a growth medium in a test tube; this provides the medium with more surface area for microbial growth

24
Q

what is meniscus

A

when a liquid is in a cylinder the liquid will be higher than in the middle creating a concave

25
Q

identify the times when a microbiologist must use a pure culture

A

1-look for a particular pathogen that caused a disease
2-to look for antibiotic susceptibilities on that pathogen
3-to inhibit evolutionary change

26
Q

describe characteristics of a properly a adjusted bunsen burner flame

A

bunsen burner produces a flame with two cones, an outer cone that is relatively colorless and an inner cone that is blue in color and should be about one inch in height

27
Q

describe the instruments microbiologists most often use to transfer microorganisms

A

inoculating loop
inoculating needle
nutrient agar slants

28
Q

what is a mohr pipette

A

they have markings that always end before the tip

29
Q

what is a serological pipette

A

have marks that continue all the way down the tip

30
Q

what is the meaning of the markings on the top end of a serological pipette

A

they indicate whether the pipette is a blow out pipette and the size and the measurement graduations of the pipette

31
Q

identify aseptic technique procedures that are performed when working with microorganisms

A

inoculating loop is placed at the tip of the inner cone until it is bright orange and then it is dragged through the flame before and after transferring a microorganism. The test tube containing the microbe is also run through the flame before and after the transfer

32
Q

explain how to protect yourself from laboratory acquired infection

A

lab coat and goggles and closed toed shoes; keep personal things away from the desk

33
Q

why is a new stock culture always made as the first incoculation from a stock culture tube

A

we make a stock culture as a duplicate cuz the stock culture that we used for transfer is no longer sterile

34
Q

what is a serial dilution

A

series of controlled transfers down a line of blank dilution, reduces the concentration of a culture(produce between 30-300 colonies when plated
provides a way to calculate the original concentration

35
Q

what is a tube with solidified agar in an upright position, as opposed to a slant

A

agar pour (deep)

36
Q

what does TNTC mean

A

too numerous to count, >300

37
Q

what does TFTC mean

A

too few to count, <30

38
Q

this is bacterial colony shaped like a double convex lens

A

lenticulate

39
Q

this means no growth

A

NG

40
Q

what does CFU mean

A

colony forming units from a single, pair or chains of bacterial cells

41
Q

this is a count viable bacteria (meat)

A

heterotrophic plate count

42
Q

this is a plate count agar, medium used to assess total number of viable growth, not a selective medium

A

standard method agar

43
Q

what is a colony forming unit

A

1 cell or a group of 2 or more cells which when plated give rise to a colony

44
Q

why are plates labeled on the bottom of the dish and inverted for incubation/storage

A

in case of lid loss, the label will still be on bacterial culture and to avoid condensation disturbance of growth as well as rehydrate bacterial colonies

45
Q

how to calculate the dilution factor for each dilution made

A

D2=V1D1/V2

46
Q

what is countable plate

A

between 30-300

47
Q

why plates with fewer or greater number of colonies are unreliable

A 
<30= not true representation of original concentration
>300= overlapping colonies can cause human error in the counting process
48
Q

what is the basic assumption made concerning the number of bacteria in the inoculum and the number of colonies on a plate

A

the number of colonies is equal to the number of bacteria transferred

49
Q

what is the formula used to determine the concentration of bacteria in the original sample after making plate counts from a dilution series

A

original cell density=colony forming units/(dilution written on tube)x(volume transferred to the plate)

50
Q

reasons a microbiolgist might wish to ascertain the number of bacteria per milliliter in a sample of meat

A

to understand the likelihood that a specific pathogen capable of causing disease will be present in the food and that the food will spoil

51
Q

maximum number of bacteria per gram of meat for the meat to be sellable

A

10^6

52
Q

what are the limitations of the procedures used to estimate bacterial numbers

A

only bacteria capable of growing in the culture medium under the environmental conditions provided will be accounted for

Microbiology Lab (25 decks)

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