Lab 4 Flashcards
what are the variations of light microscopes
phase contrast
dark field
polarizing
UV
what microscopes are used in lab
compound binocular light microscopes
compound
scopes have minimum of two magnifying lenses (ocular and objective)
binocular
two eyepieces
light
visible light from a lamp
head
supports the two sets of magnifying lenses
what are the two types of lenses the head supports
ocular and objective
what is the lens you look into
ocular
- also known as eyepiece
- 10x
monocular microscope
microscope with one ocular lens
interpupillary distance
distance between eyepieces
field of view
circle of light that you see in the microscope
what are the objective lenses
four lenses located on the revolving nosepiece
- 4x (scanning lens)
- 10x (low power)
- 40x (high power)
- 100x (oil immersion)
what does the arm support
the stage and condenser
why is the condenser used
focus the light from the lamp thru the specimen
how can the height of the condenser be adjusted
by an adjustment knob
job of iris diaphragm
controls amount of light that shines through specimen
- located on the condenser
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
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
- archaea
- 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
