Lecture 2 - Observing the Microbial Cell Flashcards
We can see ___ with the naked eye but a less than ___ we need a microscope
- Eukaryotes
- .1 mm
Describe how resolution is different than detection
-Detection is just the ability to determine the presence of an object whereas resolution is the ability to distinguish 2 objects when closely together
What are 4 different ways that light can interact with a specimen?
- Absorption ->The light does NOT pass through but rather traps the heat
- Reflection ->The light bounces OFF the specimen
- Refraction ->The light bends after passing through another substance
- Scattering ->The light goes in all different directions
Magnification relies on ____ and ____.
- Refraction
- Creating a focal point
What is empty magnification?
-It is when you go pass 500x and do NOT get any better resolution
Why use oil immersion when using a bright field microscope?
-Reduces the amount of light that refracts because the oil has the same refractive index as glass. Which allows for you to see your specimen and NOT the glass
I want to look at a specimen while it is moving in my water sample. What type of microscope could I use?
- Bright Field
- Dark Field
- Phase Contrast
List to steps for preparing a wet mount
- Take a drop of sample
- Drop a cover slip on
How is Fluorescence Microscope different than Super-Resolution Imaging?
- Fluorescence; the specimen absorbs light at one wavelength and emits it at a lower wavelength
- Super-Resolution Imaging; breaks the diffraction of light
Why would I use a Dark field microscope instead of a light microscope?
-Because the specimen is too small, too clear or we want to see the flagella
How does Phase Contrast work?
- It works by increasing the refractive index between the specimen and background
- Specimen gets darker and the background gets lighter
What does a Differential Interference Contrast give you?
a) True 3-D picture
b) Normal Image
c) Nothing
d) False 3-D picture
D
What is the difference between TEM and SEM?
- TEM shows the internal structures of a cell and produces an image by slicing
- SEM shows the surface of a cell
True or False. Using Atomic Force Microscope the specimen is alive.
True
What is the special step in creating a slide for cryo-electron microscopy?
-You have to flash-freeze the sample
True or False. The sample is alive while looking at it
False, the sample is vaporized after the electrons hit it
How many different stains can you put on a sample at once?
As may as you would like
What is a sample stain?
- Colors ALL the cells one color to help give contrast from the background
- Methylene blue is a common example
Why use a differential stain instead of a simple stain?
-Because you have only want to look at one type of cell
Describe what an acid-fast stain works on
- Stains mycobacterium
- Carbolfuchsin is a common stain
Describe a spore stain
- Detects spores
- Malachite green is a common stain
What is the staining procedure for methylene blue?
-place a few drops and then wash with water
What is the staining procedure for Gram staining?
-Place stain, add iodine, wash w/ ethanol and finally add safranin
Why does Gram-positive stain purple?
-Because the thick cell wall and the negative charge present helps the stain stay in the cell wall
