Flashcards in Lecture 4 Deck (54):
2 main types of microscopes
any microscope that uses visible light to observe specimens
Compound light microscope uses 2 lens to observe specimens
located closest to specimen, magnifies specimen, 10x-100x
lens located w/in the eye piece, magnifies the specimen 10x
objective lens X ocular lens
Example of calculating magnification for compound microscope
ocular lens= 10x
objective lens= 100x
total magnification = 10 x 100 = 1000
ability to distinguish fine detail and structure
If a microscope has a 6nm resolving power then it can distinguish two points if they are at least ...
In order for 2 objects to be seen as distinct from on another...
light must pass in between them, and be short enough wavelength otherwise only seen a 1 objects
General principle of resolution
shorter the wavelength go light the better resolution will be (inverse relationship)
uses beam of electrons, waves of electrons are much shorter than light waves, achieves greater resolution, also higher magnification
Smallest object visible w/ human eye
Compound microscope can be used to view an object as small as..
Electron microscope can be used to view objects as small as
Trasmission electron microscope (TEM)
used to examine internal cell structure
Electron beams of TEM do not penetrate thick cell wall which requires..
cell to be cut using process called thin sectioning, the thin sections must be stained before viewed to improve contrast
Scanning electron microscopy (SEM)
only be used to view surface of object, specimen must be coated w/ thin film of heavy metal, wide range of magnification to be achieved
Scanning tunneling microscopy (STM)
most powerful, visualize atoms, uses thin metal probe to scan specimens revealing surface irregularities
stain composed of -'ve or +'ve charged ions and one type of either +'ve or -'ve is coloured
1st step in staining procedure
thin film of material called smear which contains the microorganism of interest is 'smeared' on slide
2nd step of staining porcedure
sample is then find by passing though flame
3rd step of staining procedure
stain is then applied to the sample
4th step of staining porcedure
stain is remover from sample by rising
Final step in staining procedure
stained sample is now viewed under microscope
How to stains work
outer surface of bacteria carries net -'ve charge, -'ve charge attracts +'ve charge and repels -'ve charge which strains use to manipulate
+'ve charged stains will agree to -'ve changed bacterium (basic), bacteria will appear color of stain while background is clear
-'ve stain will be repelled by -'ve charged bacterium (acid) bacteria will appear clear, background will appear colored
single colored basic dye used
when the coloured ion is the ='ve ion which then binds to the organism making it appear in the color of dye (mordant used sometimes ti increase intensity)
used to differentiate in between different yes of bacteria because the stains react differently with different types of bacteria
Differential stains are very important for..
diagnostics because it exploits different in cell wall structure and composition
Examples of differential stains
gram stain and acid fast
Gram stain dtermines
whether a bacterium of interest is gram +'ve or -'ve
2 primary types of bacteria based on among of peptidoglycan in the cell wall
Gram positive have a ____ layer of peptidoglycan then gram negative
Anything gram positive = ____ and gram negative = _____
Any eukaryotic cells in gram stain will be ...
pink because negative membrane
During gram stain __ stains are used with wash(s) between them
If a bacteria is gram positive then..
the thicker layer of peptidoglycan will hold the first purple stain
If the bacteria are gram negative them..
the thin peptidoglycan will not hold the first stain w/ violet and it will be washed away, resulting in second stain (safranin) ticking and making bacteria pink
Acid fast stain
stain binds strongly bacteria that contain waxy cell wall component.
Acid fast stain is used to identify all bacteria that fall under the genus..
Waxy cell wall of mycobacterium retains the..
carbol fushin die that is added
Counterstain for acid fast
methylene blue leaves tissues and non-acidfast bacteria blue
3 types of special stains
reveals presence of thick polysaccharide layer outside of bacterial cell
Capsule presence indicates ..
bacterium w increase virulence or increase ability to cause disease in comparison to same bacteria that lacks capsule
During capsule stain background is coloured with..
a negative stain such as nigrosin which makes it black
During capsule stain bacterial cell is stained with..
a positive cell stain such as safranin making it colored
During capsule stain capsule ..
doesn't take up dye so remains colorless with halo around cell
primary stain colors endospore green, counterstain safranin colors rest pink
Example of endospore forming bacteria is