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Endotoxin

(Science: protein) heat stable polysaccharide like toxin bound to a bacterial cell. The term is used more specifically to refer to lipopolysaccharide (LPS) of the outer membrane of gram-negative bacteria. There are three parts to the molecule, the lipid a (six fatty acid chains linked to two glucosamine residues), the core oligosaccharide (branched chain of ten sugars) and a variable length polysaccharide side chain (up to 40 sugar units in smooth forms) that can be removed without affecting the toxicity (rough LPS). Some endotoxin is probably released into the medium and endotoxin is responsible for many of the virulent effects of gram-negative bacteria.