The Gram stain is used to classify cells based on differences in their ________.

The Gram stain is used to classify cells based on differences in their ________.

• A. Nucleic acids
• B. Cell membrane
• C. Capsule
• D. Peptidoglycan layer

Answer: (D)

Gram staining differentiates bacteria by the structure of their cell walls, especially the thickness and composition of the peptidoglycan layer. The dye complex is retained differently after the decolorization step: a thick peptidoglycan layer traps the dye and the cells stay purple (Gram-positive), while a thinner peptidoglycan layer with an outer membrane loses the dye and take up the counterstain, appearing pink (Gram-negative). Nucleic acids, the cell membrane itself, or capsules do not determine the differential outcome. This staining pattern reflects cell wall architecture and helps guide choices that target cell wall synthesis.

Gram staining differentiates bacteria by the structure of their cell walls, especially the thickness and composition of the peptidoglycan layer. The dye complex is retained differently after the decolorization step: a thick peptidoglycan layer traps the dye and the cells stay purple (Gram-positive), while a thinner peptidoglycan layer with an outer membrane loses the dye and take up the counterstain, appearing pink (Gram-negative). Nucleic acids, the cell membrane itself, or capsules do not determine the differential outcome. This staining pattern reflects cell wall architecture and helps guide choices that target cell wall synthesis.