Lab quiz 1 flashcards

position of your hands when carrying a microscope

one hand holds arm of microscope- one holds under the base

limit of resolution

shortest distance that two objects can’t be deemed as separate

difference between limit of resolution of light microscope and of unaided eye

light microscope 0.2 μm

human eye .1 mm or 100μm

what is the condensor

located under the stage it directs light to slide but does not affect magnitude

what two adjustments can be made to the condensor

height and diaphragm

what does height control

concentration of light- moves stage up and down

what does diaphragm control

controls the amount of light that passes through

what four procedures can be implemented to achieve the maximum resolution with the oil immersion lens

1. add immersion oil right before

2. open diaphragm completely to allow the max amount of light

3. keep condensor refocused and in the highest position to minimize lost light

4. use a blue light filter to shorten wavelength

why is it advisable to start first with the low power lense when viewing a slide

it has a broader field of view and it is easier to locate the specimen. It provides a safe distance between the slides

Why is it necessary to use immersion oil with the oil immersion lens and no other lens/objectives

immersion oil has same refracting index as glass, only immersion lens is designed for oil

what is the relationship between the working distance of an objective lens and its magnificaiton power

working distance (distance between lens and slide) decreases as magnification increases

What are some errors that can result in a dirty or broken microscope

1. using oil on other lense

2. leaving cord hanging

3. not cleaning lens

4. not cleaning occulars

5. not dusting off condensor

how does a smear preparation of cells from a liquid differ from a solid

liquid- 2 loopfuls of liquid directly on the slide

solid- 1 loopfulof water first to dilute, then one small loopful of organism

why do we limit the quantity of cells used to prepare a smear

too many cells can be too dense and difficult to see individual cell morphology

consequences of making a smear too thick

thick smear means more clusters and it’s harder to see

less light gets through

incorrect staining is possible because of trapped stain

what is the purpose of heat fixation

adhere organisms to slide and heat kill them

what problems can arise when the slide is heated in a flame before it is completely dried?

• cell lysis → distorts morphology and messes up staining procedure

what problems can arise if you forget to heat fix the slide

live bacteria on your slide

cells may wash off

what problem will you face if you apply organism to the bottom of the slide?

• glass is too thick so you will be unable to focus on the organism

• may contaminate and dirty the lens or microscope

shape of corynebacterium

rod shape

palisade arrangement

staphylococci arrangement

grape like clusters

arrangements of bacillus

chain like or singular or palisade

basic vs acidic dyes

basic are positvely charged chromophores and attract negatively charged cell → they color the bacteria

acidic are negatively charged chromophores and repel the negatively charged cell → they stain the background

what kind of stain is crystal violet

simple basic stain, purple

what would you expect to see under the microscope if viewing streptococcus pyogenes stained by crystal violet

chains of spherical cells, purple

what characteristics can be visualized with a simple stain

cell shape, arrangement and approximate size

if working only with simple stain, would you be able to know which species it is?

No, many species have identical morphologies

which objective has the highest magnification

oil immersion

which has the lowest magnification?

low power objective

which has the shortest working distance

oil immersion objective

which lens uses coarse focus

low power

which lens collects and focuses light source

condenser

which lens has diopter adjustments

ocular

diaphragm regulates light through which lens

condenser