Question:
Which of the following is true about endotoxin?
Which of the following is true about endotoxin?
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Endotoxin is a lipopolysaccharide, not a protein enzyme, and is poorly antigenic.
Updated On: Jun 24, 2026
- Protein
- Highly antigenic
- No enzymatic activity
- Produced by gram positive bacteria
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The Correct Option is C
Solution and Explanation
Step 1: Concept. Endotoxin is the lipopolysaccharide (LPS) of the outer membrane of gram-negative bacteria. Its toxic part is lipid A. Unlike exotoxins, which are secreted proteins with specific actions, endotoxin is a structural cell-wall component.
Step 2: Why no enzymatic activity. Because endotoxin is a lipopolysaccharide and not a protein enzyme, it has no enzymatic activity. It acts by triggering cytokine release, fever, and shock rather than by catalysing a reaction. So option (c) is correct.
Step 3: Why the others are wrong. Endotoxin is lipopolysaccharide, not protein, so (a) is false. It is weakly antigenic (poorly immunogenic) compared with the highly antigenic exotoxins, so (b) is false. It is produced by gram-negative, not gram-positive, bacteria, so (d) is false.
Step 4: Note. Endotoxin is heat stable and cannot be converted into a toxoid, again contrasting with heat-labile, toxoid-forming exotoxins.
Step 2: Why no enzymatic activity. Because endotoxin is a lipopolysaccharide and not a protein enzyme, it has no enzymatic activity. It acts by triggering cytokine release, fever, and shock rather than by catalysing a reaction. So option (c) is correct.
Step 3: Why the others are wrong. Endotoxin is lipopolysaccharide, not protein, so (a) is false. It is weakly antigenic (poorly immunogenic) compared with the highly antigenic exotoxins, so (b) is false. It is produced by gram-negative, not gram-positive, bacteria, so (d) is false.
Step 4: Note. Endotoxin is heat stable and cannot be converted into a toxoid, again contrasting with heat-labile, toxoid-forming exotoxins.
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