Exam 1 Objectives Flashcards by Christina Stafstrom

what is a simple microscope

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

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what is a compound microscope

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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what is the power of the objective and ocular lenses

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

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

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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describe resolving power

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

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describe numerical aperture

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

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what does the blue light equal

shorter wavelength

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

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

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describe the change in working distance as magnification increases

as magnification increases, working distance decreases

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what does parfocal mean

having corresponding focal points in all the same plane

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what is the advantage to the microscopist parfocally

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

as magnification increases, size of field decreases

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what is the field of view

how much of your subject you see through the lens

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

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

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

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

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what is meant by depth of field

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

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what is a pure culture

lab culture with one species of organism

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what is a mixed culture

lab culture with two species of organism

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what is aseptic

without contamination of culture, the sterile medium or the surroundings

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what is sterile

killing all forms of microbe life

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what is contamination

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

what is broth

used to grow stock culture

what is a slant

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

what is meniscus

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

identify the times when a microbiologist must use a pure culture

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

describe characteristics of a properly a adjusted bunsen burner flame

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

describe the instruments microbiologists most often use to transfer microorganisms

inoculating loop inoculating needle nutrient agar slants

what is a mohr pipette

they have markings that always end before the tip

what is a serological pipette

have marks that continue all the way down the tip

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

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

identify aseptic technique procedures that are performed when working with microorganisms

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

explain how to protect yourself from laboratory acquired infection

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

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

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

what is a serial dilution

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

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

agar pour (deep)

what does TNTC mean

too numerous to count, >300

what does TFTC mean

too few to count, <30

this is bacterial colony shaped like a double convex lens

lenticulate

this means no growth

what does CFU mean

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

this is a count viable bacteria (meat)

heterotrophic plate count

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

standard method agar

what is a colony forming unit

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

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

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

how to calculate the dilution factor for each dilution made

D2=V1D1/V2

what is countable plate

between 30-300

why plates with fewer or greater number of colonies are unreliable

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

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

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

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

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

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

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

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

10^6

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

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