Lab 1 Flashcards
what is in a stain
A solvent and a colored molecule called chromogen.
Chromogen? What does it contain?
Consists of a chromophore which gives the stain its color. It contains auxochrome which is the charged portion of the molecule that allows it to be dyed.
What happens when an auxochrome is positively charged? Negatively charged?
Positively charged (basic dye), bind to the cell walls which are net negative charge -> cell is colored.
Negatively charged (acidic dye) -> replusion-> resulting in the background being dyed, the cell is colorless
Purpose of heat fixation
- kill bacterial cells
- Coagulate the cytoplasmic proteins to make them more visible
- Help cells adhere to the slide
How does a microscope work?
Light source -> condenser -> specifmen -> objective lens -> ocular lens
Total magnification is?
Ocular magnification x Objective magnification
Purpose of oil immersion
Increase numerical aperature -> decrases the refraction and more light and get into the objective lens
What is the limit of resolution
Minimum distance between 2 points to distinguish them as separate entities
Calibration of microscope
Place the stage micrometer ontop of the ocular micrometer. Use the stage micrometer to measure the ocular micrometer
Smallest division of stage micrometer is
10 um
What is the numerical aperature dependent on?
Index of refraction. Higher NA -> smaller D
4x, 10x, 40x, 100x in other names:
scanning objective lens, low-power objective lens, high-dry objective lens, oil immersion objective lens
For bacteria staining, do you heat fix first or stain first
heat fix first
What is negative staining? Positive staining?
Negative staining is staining the background. Positive staining is staining the cell
Why dont you heat fix for negative staining?
because heat fixing can distort and shrink the cell
Difference in technique of negative staining and positive staining. relate to not being able to heat fix
Motile/Brownian motion
Motile: have flagellas and can move. Brownian motion: virbate in their spot
What is the mordant/Ryu stain
Stain used to stain flagella, stain adheres in layers to the flagella, allowing visualization
What is bacteria that has a single flagellum called?
a polar flagellum with monotrichous arrangememnt
Bacteria with flagella at both ends? tufts of bacteria at the end, emerging end of the cell
Amphitrichouse, lophotrichous, peritrichou
