Gram Staining

Question 1

Process of gram staining (4)

Answer 1

1. Apply crystal violet (purple dye)
2. Apply iodine (mordant)
3. Alcohol wash (decolorisation)
4. Apply safranin (colourisation)

Question 2

Why does the purple dye not stick the negative gram?

Answer 2

It dyes the outer membrane but the alcohol breaks this down leaving the peptidoglycan exposed exposed. This is what the pink dye sticks to

Question 3

Difference between gram positive and gram negative (structural)

Answer 3

Gram positive have a thick outer layer of peptidoglycan whereas gram negative have a thin layer of peptidoglycan surrounded by an outer membrane