Lab 4 Flashcards by Emma Fischer

what are the variations of light microscopes

phase contrast
dark field
polarizing
UV

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what microscopes are used in lab

compound binocular light microscopes

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compound

scopes have minimum of two magnifying lenses (ocular and objective)

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binocular

two eyepieces

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light

visible light from a lamp

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head

supports the two sets of magnifying lenses

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what are the two types of lenses the head supports

ocular and objective

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what is the lens you look into

ocular
- also known as eyepiece
- 10x

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monocular microscope

microscope with one ocular lens

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interpupillary distance

distance between eyepieces

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field of view

circle of light that you see in the microscope

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what are the objective lenses

four lenses located on the revolving nosepiece
- 4x (scanning lens)
- 10x (low power)
- 40x (high power)
- 100x (oil immersion)

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what does the arm support

the stage and condenser

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why is the condenser used

focus the light from the lamp thru the specimen

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how can the height of the condenser be adjusted

by an adjustment knob

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job of iris diaphragm

controls amount of light that shines through specimen
- located on the condenser

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how should you fix the problem of too much light reducing the contrast of the image seen

adjust the iris diaphragm to restrict the amount of light directed thru the condenser lens

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light intensity knob

controls amount of light allowed to pass thru lens

stage

supports specimen collection

slide movement knobs

move slide across the stage

how can the distance between the stage and objective be adjusted

coarse and fine focus knobs

base

acts as a stand to house the lamp

what are the general rules of microscope use

carry microscope with 2 hands and hold it at the arm
adjust the microscope for your personal use
check the lenses and possibly need to clean with dry lens paper
be careful with water
don’t be forceful

what is the process to mount a slide

make sure stage is as far down as it can go
lower stage thru coarse focus knob
secure slide with slide clip on stage
move slide around until object observed is illuminated

how to use a compound microscope

- rotate the scanning (4x) objective lens into place as you always begin with lowest power - bring stage toward objective lens - focus downward using coarse focus knob - use fine focus knob to bring specimen into focus - switch to higher magnification if needed

total magnification

product of objective lens magnification and ocular lens magnification

what is the relationship between field of view and working distance with magnification

as magnification increases, these decrease

why is oil used on 100x

- oil has the same refractive index as glass, so when the light moves from light to oil, it doesn't bend - increases resolution of image

how should you properly put away a microscope

- clean lenses with dry lens paper - reduce light intensity to lowest - lower stage all the way down - turn revolving nosepiece so that 4x is in place

what should you never do when handling microscope

- do not turn on the light switch until light intensity is at lowest level - never use coarse focus with any objective above 10x - never use kimwipes - never leave oil on lens

bacteria

- prokaryotic cell - small - have ribosomes - missing membrane bound organelles - simple - true bacteria

what are the two types of prokaryotes

1. archaea 2. bacteria

archaea

ancient bacteria - live in extreme conditions

what are the three groups of bacteria

group 1: possess thick cell wall and are gram positive group 2: possess thin cell wall and are gram negative group 3: lack cell walls are referred as mycoplasmas

bacteria colony

- grows from single bacterium - composed of millions of cells - each colony exhibits morphology

what are the ways to identify bacteria colonies

form elevation margin

what are the common bacterial shapes

- bacillus (rod) - coccus (sphere) - spirillum (spiral)

gram negative bacteria

- contain less peptidoglycan - more complex cell wall - have lipopolysaccharide cell layer - lose purple/blue stain - retain safranin - appear pink/red

gram positive bacteria

- thicker peptidoglycan layer - retain crystal violet/iodine stain - simple cell wall - no outer lipopolysaccharide wall layer - appear purple/blue

what must be done before gram staining

bacteria must be spread across a slide and heat fixed

what is the process for gram staining

- place slide in staining tray - cover smear with crystal violet for 1 minute - rinse with water - cover smear with gram's iodine for 1 minute. pour off stain but do not rinse - cover smear with 95% ethyl alcohol for 15 sec - gently rinse with DI water - cover smear with safranin for 1 min - rinse with DI and dry

safranin

- red color - non selective stain - binds to everything (+) or (-)

crystal violet

binds to peptidoglycan