week 4 quiz

what does size of microscope depend on

size of specimen, light source, and resolving power

light source

generate contrast

contrast

differentiate object fro background

true or false: most specimens are colorless

TRUEr

resolving power

distinguish two close points as two separate points

what formula is used for resolving power

reyleigh formula

reyleigh formula

d _min=0.6λ/NA=0.61λ/nsinθ

n

refractie index of medium through which light passes

high resolving power

d_min is smaller but high resolving power

resolving power of eyes

200um (0.2mm)

eukaryote size resolving power

10-100um

prokaryote resolving power

0.5-2

light microscope

study microbes including bacteria in labratory

max magnification for light microscope

1000

what type of specimens can light microscope see

live or dead

four different objective lenses for microscope

4,10,40,100

how many ocular lens

1

objective lens

defines magnification or apparent increase in size of image

what does not contribute to magnification

condenser lens

condenser lens

focuses light onto specimen

brightness of light if using lower magnification

lower intensity as opening of lens is larger and can grab more light

brightness of light if using higher magnification

increase the light

what is brightness of light controlled by

light bulb or iris diaphragm

true or false: all light that passes through objective is collected via the objective lens

FALSe, refracted

what does the amount of light reaching objective lens depend on

refractive index

low magnification refractive index

low as medium between objective and specimen is air → low resolutio and contrast

immersion oil

replace air between specimen to minimize loss of light

immersion oil fractive index

same as glass

wet mount

clean glass slide, add drop of suspension w specimen and overlay with coverslip

most common ways to use a light microscope

wet mount

what can you view for wet mount

live cells, shape, arrangement, mobility

limitation of wet mount

specimen is usually colorless → staining

staining specimen

sample is dried on glass slide, heated or fixed

two ways to heat or fix specimen

slide warmer or flame

two ways of staining

simple and differential

simple staining

single dye to stain fixed specimen

examples of simple staining

methylene blue, malachite green, crystal violet, safranin

acidic dyes

stain background for contrast

ex differential staining

gram and acid-fast

dr hans christian gram

staining lung tissues of patients with pneumonia to determine cause

what is bacteria cell wall made of

glycan chains → NAM and NAG

tetrapeptide

4 amino acids in NAM

transpeptidase enzyme

connect tetrapeptides in NAM → 3D PDG structure

what do gram - bacteria have

cell membrane, periplasmic space, outer membrane

outer membrane of gram -

asymmetrical with two different leaflets, proteins connect

leaflets of gram -

phospholipid inner

LPS outer

gram staining steps

• bacterial smear on glass slide → heat fixed

  • crystal violet, iodine, alcohol staining

why is iodine used for gram staining

mordant or fixative

what do crystal violet and iodine form

large complex (CVI) trapped in PDG

result of using alcohol for gram staining

gram - → lose CVI

gram + → retain

resulting colors of bacteria after staining

positive → purple/dark blue

negative → pink/red

what can also be determined for bacteria after staining

shape and arrangement

what is applied to gram - bacteria before viewing under microscope

counterstian (safranin)

why use cuonterstain for gram -

lose ability to be seen under microscope

types of arrangements for bacteria

diplococci, chians, packets, clusters

shapes of bacteria

cocci, bacillus, spirillum