Lipid A-11 is a lipid component of endotoxin that is primarily responsible for the toxic properties of gram-negative bacteria. Lipid A-11 constitutes the innermost region of the lipopolysaccharide (LPS) molecule, also known as endotoxin, and its hydrophobic nature facilitates anchoring of the LPS structure into the bacterial outer membrane. Lipid A-11 plays a critical role in host-pathogen interactions, contributing to septic shock and immunological activation during bacterial infections.