Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
22 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
Why can't unstained microorganisms be seen under the ordinary microscope |
Because their refractive index is nearly similar to that of the suspending medium |
|
|
|
What is the use of stains |
To create contrast between cell and medium |
|
|
|
Stains can be?
|
Acidic, basic or neutral |
|
|
|
The commonly used stains are? |
They are chemical salts of organic (aromatic) compounds possessing colour |
|
|
|
Basic stain consists of? |
A colored base (a cation) and a colorless acid radical (an anion) |
|
|
|
Examples of basic stains include? |
Methylene blue chloride, crystal (gentian) violet and basic safranin. |
They are 3 |
|
|
What type of stain is commonly used to stain bacteria. |
They are basic stains because bacterial cells are rich in nucleic acids (bearing negative charges as phosphate groups) which combine with the positively charged basic dyes. |
|
|
|
List examples of acidic stains |
Eosin dye, nigrosin, Indian ink, picric acid, Congo red and acid fuchsin |
They are 6 |
|
|
Ziehl Neelsen differentiate acid fast from non acid fast bacteria while the schaeff Fulton does -? |
Reveal bacteria endospore |
|
|
|
The feulgen technique does -? |
Reveal nuclear material |
|
|
|
What is materials does negative staining technique incorporate? |
Indian pink or at most Nigrosin |
|
|
|
What is the working principle of negative staining? |
Staining the background with an acidic dye, leaving the cells contrastingly colourless. |
|
|
|
In plant and animal tissue, what is the width of the thin layer? |
5-10 micrometer thick Using a microtone |
|
|
|
Why should a small portion of growth (about the size of a pin head)be removed when making a smear from a solid media |
In order to avoid the problem of getting too many cells |
|
|
|
Why does fixation stop all enzymatic activity in the cell before observation. |
Enzymes destroy cell structure. |
|
|
|
What chemicals can be used in fixation |
Formaldehyde and potassium permanganate. |
|
|
|
What are the two disadvantages of heat fixation? |
1) it damages organisms and alter their staining reaction esp if excess heat is used. 2)it damages leucocytes and is unsuitable for fixing smears which contains intracellular organisms such as Neisseria gonorrhea and Neisseria meningitidis, Mycobacterium tuberculosis. |
|
|
|
When is alchohol fixation recommended for fixing smears? |
When looking for gram negative intracellular diplococci e.g N.gonorrhea or N.meningitidis |
It is more bactericidal than heat |
|
|
What is Carbol-fuchsin |
A basic fuchsin dissolved in phenol-acid-water mixture. |
|
|
|
In the spore staining technique: Vegetative cells take up _colour? Spores take up_colour? |
1) color of counter stain (red for safranin) 2)spores retain the color of the primary dye. |
|
|
|
Welch method is a capsule staining technique which involves? |
Treatment with hot Crystal violet solution followed by rinsing with copper sulphate solution. |
|
|
|
In the cell wall stain, we immerse thick smear in-? For how many minutes? At the end cell wall stains-? Cytoplasm stains- |
1% phosphomolybdic acid For 3-5 minutes And in 1% methyl green For 3-5 minutes Cell wall stains dark green or purple Cytoplasm is unstained |
|
