If you performed a Gram stain on human cells, what would happen?

If you performed a Gram stain on human cells, what would happen?

• A. They would appear purple
• B. They would appear pink
• C. They would appear as false positives
• D. They would fluoresce

Answer: (B)

Gram staining differentiates cells by their cell wall structure, specifically the presence of a thick peptidoglycan layer that traps the crystal violet-iodine complex. Human cells are eukaryotic and lack that bacterial-type wall, so they do not retain the purple dye after decolorization. They become decolorized and then pick up the pink counterstain, so they appear pink. They do not fluoresce under this protocol, and the idea of a false positive doesn’t apply to how human cells would behave in this stain. Pink is the expected appearance.

Gram staining differentiates cells by their cell wall structure, specifically the presence of a thick peptidoglycan layer that traps the crystal violet-iodine complex. Human cells are eukaryotic and lack that bacterial-type wall, so they do not retain the purple dye after decolorization. They become decolorized and then pick up the pink counterstain, so they appear pink. They do not fluoresce under this protocol, and the idea of a false positive doesn’t apply to how human cells would behave in this stain. Pink is the expected appearance.