Which of the following statements about exotoxins is generally false?

• A. Exotoxins can be produced by both Gram-positive and Gram-negative bacteria.
• B. Exotoxins are proteins secreted by bacteria.
• C. Exotoxins often have specific targets and effects within the host.
• D. Exotoxins are typically heat-stable and resistant to denaturation.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand what exotoxins are. Exotoxins are toxic proteins secreted by bacteria that can cause damage to the host by targeting specific cells or systems.
2. Step 2: Review the characteristics of exotoxins. They are generally proteins, secreted actively by both Gram-positive and Gram-negative bacteria, and often have specific targets and effects within the host.
3. Step 3: Consider the heat stability of exotoxins. Unlike endotoxins, exotoxins are usually heat-labile, meaning they are sensitive to heat and can be denatured or inactivated by it.
4. Step 4: Analyze the given statements. The statement claiming exotoxins are typically heat-stable and resistant to denaturation contradicts the known property that exotoxins are heat-labile.
5. Step 5: Conclude that the false statement is the one about exotoxins being heat-stable, as this is not generally true for exotoxins.