Stains Flashcards Preview

Bio 346 > Stains > Flashcards

Flashcards in Stains Deck (16):

What is an auxochrome?


  • component of dye that does not produce color but gives the dye its acidic or basic (electron donor or acceptor) properties.
  • Examples are electron donors or acceptors that extend the conjugated system of the chromophore.
    • NH2
    • OH
    • OCH3
    • I
    • Br
    • Cl


What is a chromophore?


  • component of dye that imparts color to the dye molecule
  • these are usually resonant structures that can absorb light and UV over certain wavelengths.
    • Transmission of the remainder of the spectrum gives them their characteristic colors.


Circle the  auxochrome groups in the following stains:


What is the point of Simple staining?

  • Simple staining is merely the use of a dye to increase the contrast of cells for microscopy.
  • As an example, a simple stain would be used to detect the presence of bacteria in some natural material such as urine or water.
  • It must be remembered that a simple stain alone is not useful as an identification tool.


What is a mordant?


  • a chemical compound that reacts with the stain to form an insoluble, colored precipitate.


  • We most often use ________ (anionic/cationic) stains to examine bacteria. as ________ (anionic/cationic) stains are much less common and are used only for special purposes.

  • We most often use cationic stains to examine bacteria. as anionic stains are much less common and are used only for special purposes.


What is the purpose of this stain:


Coomassie blue

Coomassie blue

  • stains proteins a brilliant blue
  • Can be used to estimate the amount of protein in a solution (Bradford Assay)


What is the purpose of this stain:


Crystal violet

Crystal violet

  • stains cell walls purple when combined with a mordant.
  • This stain is used in Gram staining


What is the purpose of this stain:


Malachite green

Malachite green

  • a blue-green counterstain to safranin
  • used to stain spores.


What is the purpose of this stain:


Methylene blue

Methylene blue

  • stains animal cells to make nuclei more visible.


What is the purpose of this stain:




  • a simple stain to visualize bacterial cells.


What are the differences between these types of stains?

  • simple staining
  • negative staining
  • differential staining
  • background staining
  • capsule staining


What is the purpose of this stain:


Congo Red

  • Capsules can be observed by negative stains or by combining a negative stain and a simple stain.
  • “Negative stains” such as India ink, nigrosin and Congo Red stain the background but not the bacterial cells or capsules.


What is Maneval’s solution?

Maneval’s solution?

  • The staining method in which the outer layer of cell wall (ie capsule) is stained is called capsule staining by Maneval's method.
  • It is a counterstain, allowing for congo red's color to change from blue to red in basic to acidic conditions. 


What is the point of steaming during spore staining?

  • Endospores are impervious to most ordinary stains.
  • Malachite green is placed on a bacterial smear and heat (form the steam) is used to drive the dye into the spores.