Which of the following statements best explains the difference in LD50 values between exotoxins and endotoxins?

• A. Exotoxins have a much lower LD50 than endotoxins, meaning they are more potent.
• B. Exotoxins and endotoxins have similar LD50 values, indicating equal toxicity.
• C. Endotoxins have a much lower LD50 than exotoxins, meaning they are more potent.
• D. LD50 values are not used to compare the potency of exotoxins and endotoxins.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand what LD50 means. LD50, or lethal dose 50, is the amount of a toxin required to kill 50% of a test population. A lower LD50 indicates higher potency because less toxin is needed to cause death.
2. Step 2: Review the characteristics of exotoxins. Exotoxins are proteins secreted by bacteria, often highly specific and potent, and can cause damage at very low concentrations.
3. Step 3: Review the characteristics of endotoxins. Endotoxins are lipopolysaccharide components of the outer membrane of Gram-negative bacteria, generally less potent and released mainly when bacteria die and lyse.
4. Step 4: Compare the LD50 values of exotoxins and endotoxins. Since exotoxins are more potent, their LD50 values are much lower than those of endotoxins, meaning smaller amounts cause lethal effects.
5. Step 5: Conclude that the statement 'Exotoxins have a much lower LD50 than endotoxins, meaning they are more potent' best explains the difference in LD50 values between these two toxin types.