3.2 Sample Detections: Staining Flashcards
What can stains be used to examine?
muscle tissues
connective tissues
specific types of cells
organelles
Who first developed Gram staining?
Hans Christian Gram
When was Gram staining developed?
1884
What cells use Gram staining?
bacteria
What are the two subcategories of Gram staining?
gram negative
gram positive
What is the structure of gram positive bacteria?
thick cell wall with many overlapping strands of peptidoglycan
What is the function of a thick peptidoglycan cell wall?
protective barrier to the surrounding environment
What is the Gram stain composed of?
dye combinations of crystal violet and iodine
What color do gram positive cells appear?
purple
Why do gram positive cells appear purple?
crystal violet gets stuck in the peptidoglycan and forms a stable complex when the iodine is added trapping the dyes in the cell
What is the structure of gram negative bacteria?
thin peptidoglycan layer followed by an outer membrane composed of lipopolysaccharides
What color do gram negative bacteria appear?
unstained
Why do gram negative bacteria appear unstained?
the crystal violet retained originally is washed away during the alcohol wash
How do we visualize gram negative bacteria is gram staining does work?
safranin dye
What color do gram negative bacteria appear after being dyed with safranin?
pink
What is a differential stain?
generalized term used for any staining technique that separates specimens into further subgroups
What is a disadvantage of gram staining?
requires the cells to be fixed to a glass side
What is the most common method of fixing a sample?
heat fixation
What is the process of heat fixing?
samples are added to a glass slide and then passed through a flame until all liquid in sample has been removed
What is the process of chemical fixation?
using paraformaldehyde, ethanol, or methanol
