types of cells, microscopes, gram staining lab Flashcards
cell theory
All organisms are made of one or more cells.
Cells are the basic unit of structure and function in living things
Cells arise by division of pre- existing cells
how do we study cells?
cytology
2 main types of microscopes
light and electron
2 types of electron microscopes
transmission (TEM)
scanning electron (SEM)
light microscope features: how does it work? magnification? can specimen be alive? can you see organelles?
Visible light passes through specimen
Refracts light so specimen is magnified
Magnify up to 1000X
Specimen can be alive/moving
Can’t see organelles
other than nucleus
electron microscope features: how does it work? magnification? can specimen be alive? can you see organelles?
Focuses a beam of electrons through/onto specimen
Magnify up to 1,000,000 times
Specimen non-living and in vacuum
Can see organelles
can light or electron microscopes magnify better?
electron
transmission microscope features
2-D, study internal structures of cells
Creates a flat image with extreme detail
Can enhance contrast by staining atoms with heavy metal dyes
Images called a micrograph
scanning microscope features
3-D
Used for detailed study of surface of specimen
Gives great field of depth
Sample covered with thin film of gold, beam excited electrons on surface
2 main types of cells
eukaryote
prokaryote
prokaryotes domain
bacteria and archaea
eukaryotes domain
eukarya (protists, fungi, plants, animals)
prokaryote features
No nucleus (Nucleoid-DNA concentration)
DNA in a nucleoid
Cytoplasm/Cytosol
No organelles other than ribosomes
Small size
Primitive
i.e. bacteria
eukaryote features
Has nucleus and nuclear envelope
Cytoplasm/Cytosol
Membrane-bound organelles with specialized structure/function
Much larger in size
More complex
i.e. plant/animal cell
staining
process when color is added to bacteria so you can see it under a microscope
gram-staining
almost always the first test performed for the identification of bacteria. the bacteria are identified as gram positive or negative based on the amount of peptidoglycan it has. it is a specific technique invented by Hans Christian Gram
what is the cellular difference between gram positive and negative bacteria?
positive: several layers of peptidoglycan
negative: one layer
process of gram staining:
- specimen is heat fixed to the slide
- use a primary stain on the slide
- use a counter stain (secondary stain) on the slide
- mordant is used to seal the stain into the bacteria
- a decolorizer is used to remove excess stain
heat fixing
process of passing the side containing the specimen through heat 2-3 times to make it stick to the glass slide
what happens if you heat fix for too long?
the cytoplasm will boil, resulting in the destruction of bacteria cells, making staining and identification impossible
what is the primary stain of the gram staining method?
crystal violet (sometimes methylene blue)
what is the most common counter stain of the gram staining method?
safranin red/basic fuchsin
what colors will the bacteria appear in the gram staining method?
positive: purple
negative: red
reason: all bacteria stained by crystal violet appear purple, all unstained bacteria are affected by safranin red and appear red.
mordant
chemical used to seal the stain into the bacteria. this helps so the stain cannot be easily removed
what mordant is used in the gram staining method?
gram’s iodine
decolorizer
chemical used to remove excess stain
what is the decolorizer used in gram staining?
ethyl alcohol
what happens if you leave the stain or decolorizer on the bacteria for too long?
too light/dark stain
too little/too much removal of stain
true/false: chemicals lose their effectiveness over time
true
