Cell structure Flashcards
How to stain slides?
- Allow to dry
- Heat it by a Bunsen burner
Why are samples cut into sections?
To allow light to pass through easily
Where is crystal violet used?
Stains cell walls purple, used in gram staining
Where is methylene blue used?
Stains nucleus of animal cells to give contrast
Where is Congo red used?
Negative stain that is not taking by the cell but provides a contrast between the cell and the background
Dry mount
Solid specimens, thin slices called sectioning, coverslip on top
Wet mount
Wet specimens, suspended in water or oil, coverslip placed on an angle
Squash mount
soft specimens, wet mount squashed between the slide and coverslip
Smear mount
the edge of the slide is used to smear the sample creating an even coat
Which object is divided into 100 sections?
eyepiece graticule
Equation for magnification factor
1 graticule division = number of micrometers ÷ number of graticule division
Equation for measurement
graticule divisions x magnification factor = measurement (µm)
Define resolution
Resolution is the ability to distinguish between two separate points
The concept of resolution
Limit of resolution is about one half of the wavelength of the radiation used to view the specimen
Define magnification
Magnification is how many times bigger the image of a specimen observed is in compared to the actual (real-life) size of the specimen
What are the two types of lenses?
- A series of (usually 3) objective lenses, each with a different magnification
- An eyepiece lens, which often has a magnification of x10
TEM (transmission electron microscope)
uses beams of electrons that pass through the specimen before being viewed. Only those transmitted are seen. It allows us to see thin sections of specimens (inside the cell).
SEM (scanning electron microscope)
an electron beam is used to scan the surfaces of structures and only the reflected beam is observed.
Light microscope procedure
Shine light through specimens, this light is passed through the objective lens (changeable) and then through the eyepiece lens (x10)
Resolution of electron microscope
0.5 nm
Resolution of light microscope
200 nm
Which microscope uses vacuum? Why?
Electron microscope, because if there was air the electrons would scatter all around
