Which of the following is the substance referred to as endotoxin?

• A. Teichoic acid
• B. Capsular polysaccharide
• C. Lipopolysaccharide (LPS)
• D. Peptidoglycan

Answer: (C)

Verified step by step guidance

1. Understand that endotoxins are toxic substances associated with the outer membrane of certain bacteria, specifically Gram-negative bacteria.
2. Recall that endotoxins are not secreted but are part of the bacterial cell structure, released mainly when the bacteria die and the cell wall breaks down.
3. Identify the chemical nature of endotoxins: they are lipopolysaccharides (LPS), which consist of a lipid component (lipid A) and a polysaccharide component.
4. Compare the options given: Teichoic acid is found in Gram-positive bacteria cell walls, capsular polysaccharide is part of the bacterial capsule, and peptidoglycan is a structural polymer in bacterial cell walls but not an endotoxin.
5. Conclude that the substance referred to as endotoxin is Lipopolysaccharide (LPS), which is characteristic of Gram-negative bacterial outer membranes.