How come some stains color specific cell structures and not others-in cells?

Question

Also, which structure would apper lighter and darker if a water-solube stain were used?

Also, which structure would apper lighter and darker if a water-solube stain were used?

Would diffusion or osmosis have anything to do with it?

Would diffusion or osmosis have anything to do with it?

Answer 1

Organelles absorb more stain due to their molecular structure. For instance, the cell walls of plants are made of cellulose. This fibrous material absorbs stain well. Organic substances, such as cells, contain proteins, fats, and carbohydrates. Depending on the specific composition, the organelle will absorb more of less of the dye.

Answer 2

Histochemistry is based on the interactions between the cellular structures and stains or mordants. Stains react with cellular components a number of different ways- some based on charge, some based on solubility, some based on certain metals being able to bind certain substrates. Sometimes this interaction is directly with the stain, though often, it is mediated by a mordant. A mordant is a metal ion that binds specific parts of the cell and the stain then binds the mordant- hematoxylin works this way. Commonly used mordants include aluminum, chromium, lead, iron and potassium.


I am not really sure what structure you are getting at with the lighter and darker- virtually all histological stains are water soluble, any non-water soluble stains I can think of are rarely if ever used for histo/cytochemistry...