Test 1 Ch 3: Microscopes Flashcards
Metric System
- We use this
1 meter/1,000,000 micrometer
Compound light microscope naming
- Compound = more than 1 lens
- Light = the source of ilumination
What is the pathway of light from the bottom of the microscope to the eye?
Illuminator –> condenser –> focuses light on specimen –> objective lens –> magnified by ocular lens –> eyeball
Acidic dye
Negative ion has color
Basic dye
Positive ion has color
Immersion oil
Used for 1000x; traps and forces more light into the objective so you can see it
Fixing
Prevents microbes from being washed off during staining; kills microbes :(
Resolution
ability of a lens to distinguish 2 points that are a specific distance apart
How do you calculate total magnification?
multiply: objective lens magnification and ocular lens magnification
Basic dyes
The positive ion has color (chromophore)
Acidic dyes
The negative ion has color
What type of dye do you use to stain bacteria? (acidic or basic)
Basic
Bacteria has a slightly negative charge (pH is 7); positives and negatives attract
Simple stain
Uses one basic dye so that the specimen has color and the background is white
Negative stain
Uses one acidic dye so that the specimen is white, and the background has color
What 3 things do simple and negative stains tell you?
- Size
- Morphology (shape)
- Arrangement (position of cells in relation to each other)
What are differential stains used for?
Used to differentiate bacteria based on other characteristics other than what a simple or negative stain tells you
What are the 2 types of differential stains?
- Gram stain
- Acid-fast stain
What is a gram stain?
- Created by Hans Christian Gram
- Divides bacteria into 2 groups: gram positive and gram negative, which are based on what color the cells end up
What is the first step in a gram stain and what color is the specimen?
- Dye: Crystal violet
- Purple
What is the second step in a gram stain and what color is the specimen?
- Chemical: iodine
- Color: purple
- Acts as a mordant –> enhances the stain
- All cells take up iodine and the purple cells stay purple
What is the third step in a gram stain and what color is the specimen?
- Chemical: Decolorizer (alcohol)
- Gram positive cells stay purple, gram negative cells are colorless
What is the fourth step in a gram stain and what color is the specimen?
- Chemical: dye called safranin
- Color: reddish/pink
- Gram positive cells are purple, gram negative cells are reddish/pink
What is an acid fast stain?
- Type of differential stain
- Binds with bacteria that have a waxy cell wall
- Myobacterium (Leprosy, TB)
- Fushia dye, decolorizer, counterstained blue
- Decolorizer: acid alcohol
What is a structural stain?
A stain that shows the presence or absence of specific structures that the bacterium may have
What are the 3 examples of structural stains?
- Capsule staining
- Endospore staining
- Flagella staining
What does brightfield microscopy use?
Light
What is dark field microscopy?
- Direct light is blocked
- Specimen is lit up
- Used to examine specimens that are unstainable or distorted by staining
What is phase-contrast microscopy?
- Detailed examination of living organisms
- Combines dark and bright field microscopy
- Gets a 3D image
What is differential interference microscopy (DIC)
Similar to phase-contrast but has 2 light sources and prisms (color contrast)
What is fluorescence microscopy?
- Uses UV light
- Can use to differentiate between T and B cells
- uses fluorochromes
What is fluorescence microscopy?
- Uses UV light
- Has properties of fluorescence
- One plane of a specimen is illuminated at a time
- Computer reconstructs into 3D image
What is scanning acoustic microscopy (SAM)?
- Scanning = reflecting off specimen
- Acoustic = sound waves instead of light
- Works similar to ultrasounds
What are 2 types of electron microscopy?
Transmission electron microscopy (TEM) and scanning electron microscopy (SEM)
What is electron microscopy? ($$$)
- Uses beam of electrons instead of light
- Electrons allow to see more detail because it has a smaller wavelength than that of light
- Greater resolution, greater magnification, greater cost
What is transmission electron microscopy (TEM)
- Transmission = what you use for illumination passes through the specimen
- Electrons pass through specimen
- Specimens must be super thin
- 0.2 nm resolution; 10,000-100,000x magnification
What is scanning electron microscopy? (SEM)
- Electrons are directed over the surface of the electron
- Good for cell surface structures
- 3D appearance
- Lower quality than TEM
- 0.5 nm resolution; 1,000-500,000x magnification
