Q. Basophilic stains like hematoxylin stain the nucleus blue – but why is the nucleus the only basophilic organelle in the cell? If it has to due with DNA charge, why are ribosomes not also stained?
A. I LOVE staining questions! Ribosomes do indeed stain blue due to their RNA content. However, the eosinophilic cytoplasmic constituents often outweigh/outnumber ribosomes, and the blue of the ribosomes is not usually visible. If the cell is making a lot of protein, though, and the ribosomes are really active, then the cytoplasm of the cell will start to take on a purple (blue plus pink) or blue color. Plasma cells, for example, make a ton of antibodies – so their cytoplasm has a nice blue-purple color.