Staining Flashcards
Outline cell theory.
- Plant + ani tissue is composed of cells
- Cells = basic unit of life
- Cells develop from existing cells
What are the components of a light microscope?
- Eyepiece
- Body tube
- Arm
- Low, med, high power
- Stage
- Stage clips
- Diaphragm
- Coarse + fine adj
- Light source
- Base
Define staining. What is it’s purpose?
- Artificial colouring of a substance
- Increases contrast to observe and differentiate between diff tissues, cells, and subcellular structures under a microscope.
What is gram staining?
Method of staining that aims to classify bacteria by the composition of their cell wall.
What is the main difference between gram positive and gram negative bacteria?
- Pos = THICK peptidoglycan layer - allows it to take on + hold purple dye from crystal violet stain
- Neg = THIN peptidoglycan layer + outer lipopolysaccharide layer (inc poss of being antibio resistant)
How thick are the peptidoglycan layers in gram positive and gram negative bacteria?
- Pos = up to 80 nm
2. Neg = less than 10 nm
Give an example of gram positive and gram negative bacteria.
- Pos = staphylococcus - staph infection
2. Neg - e.coli
Outline the process of gram staining.
- Apply primary stain = crystal violet
- Apply mordant (iodine) - fixes the dye
- Decolourisation - alcohol washes out dye but is retained by gram pos bact b/c peptido layer
- Apply counterstain (safranin) - stains bact that didn’t retain primary stain PINK i.e gram neg bact
Which alcohol is used during decolourisation?
Ethanol or acetone
What is the acid-fast technique used for?
Mycobacterium - cause TB
- AKA acid-fast organisms - have high conc of mycolic acid in cell wall
Outline the process of the acid-fast technique.
- Apply primary stain (carbol fuschin) - stains red
- Apply mordant (heat) - fixes dye
- Decolourisation - acid alcohol washes out dye but is retained by acid-fast orgs b/c mycolic acid
- Apply counterstain (methylene blue) - stains non acid-fast orgs BLUE
What is a basic stain? Give 4 examples of these.
- Basic = Stains neg charged molecs + struct e.g. nucleic acids + prot - creates POSITIVE STAIN
- Crystal violet
- Safranin
- Methylene blue
- Carbol fuschin
What is an acidic stain? Give two examples of these.
- Acid = stains pos charged molecs + struct e.g prot - creates POS or NEG stain dpending on cell’s chemistry
- Acid fuschin
- Congo red
What is a negative stain? Give 2 examples of these?
- Stains bg not specimen - creates dark bg, light specimen
- India ink
- Negrosin
Acid fast and gram staining are examples of what?
Differential staining
