Gram-negative cell walls have an outer membrane that contains lipids and peptidoglycans.

Gram-negative

Refers to bacteria that have a specific cell wall structure which does not retain the crystal violet stain used in Gram's method of staining; often associated with higher resistance to antibiotics.

Lipids

A broad class of biomolecules that are insoluble in water and include fats, oils, and cholesterol, playing key roles in energy storage and cell structure.

Peptidoglycans

A complex polymer of amino sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, providing structural support and shape.