2.1 Microscopy Flashcards
dry mount
- solid specimens are sectioned
- cover slip is placed over sample
- for: muscle tissues/ plants
wet mount
- specimens suspended in water/oil immersion
- cover slip is placed from an angle
- for: aquatic samples
squash slides
- wet mount is prepared
- lens tissue used to press down cover slip
- for: soft samples
smear slides
- edge of slide used to smear a sample
- cover slip is placed on top
- for: blood
purpose of staining
increase the contrast as different components take up stains to different degrees
how to prepare sample for staining
- place on slide to air dry
2. pass through a flame to heat fix
positive stain technique
- crystal violet / methylene blue
- attracted to negatively charged materials in the cytoplasm
negative stain technique
- nigrosin / congo red
- repelled by negative charge of cytosol so stain outside of cells making them stand out against background
why is differential staining used
to distinguish between 2 types of organisms or different organelles
what does the gram stain technique do
separate bacteria into gram-positive and gram-negative
gram-stain technique method
- apply crystal violet
- apply iodine to fix the dye
- wash with alcohol
gram positive bacteria
retain crystal violet and stay blue
gram negative bacteria
- lose stain due to thin cell walls
- are counterstained with Safranin dye to become red
difference between gram positive and negative bacteria
gram positive = susceptible to the antibiotic penicillin as it inhibits formation of cell walls
what does the acid-fast technique do
differentiate species of mycobacterium from other bacteria
