Biology – 2.1 Cell structure | e-Consult
2.1 Cell structure (1 questions)
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Gram-positive and Gram-negative bacteria differ significantly in their cell wall structure, which is the basis for the Gram staining technique. Here's a comparison:
| Cell Feature | Gram-Positive Bacteria | Gram-Negative Bacteria |
| Cell Wall | Thick layer of peptidoglycan. | Thin layer of peptidoglycan. |
| Outer Membrane | Absent. | Present. Contains lipopolysaccharide (LPS). |
| Periplasmic Space | Narrow. | Wide. |
| Gram Stain | Stains purple. | Stains pink/red. |
Diagram:
[Image missing: Gram-positive and Gram-negative cell walls]
Contrast: Gram-positive bacteria have a thick peptidoglycan layer, which retains the crystal violet stain, resulting in a purple color. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing LPS. The outer membrane is not effectively stained by the crystal violet, so they appear pink/red after the counterstain.