Which statement correctly differentiates endotoxins from exotoxins?

Which statement correctly differentiates endotoxins from exotoxins?

• A. Exotoxin is secreted by both Gram-positive and Gram-negative bacteria; heat-labile.
• B. Endotoxin is released during cell lysis; LPS; Gram-negative bacteria; heat-stable.
• C. Endotoxins are proteins produced by bacteria.
• D. Endotoxins never present in Gram-negative bacteria.

Answer: (B)

Endotoxins and exotoxins differ in what they are, where they come from, and how they’re released. Endotoxins are parts of the bacterial outer membrane, specifically lipopolysaccharide (LPS), found in Gram-negative bacteria. They are not secreted proteins; they’re released mainly when the bacteria lyse or shed membrane components. Because they’re a structural lipid–polysaccharide complex, endotoxins are heat-stable. Exotoxins, on the other hand, are proteins produced inside bacteria and actively secreted into the surrounding environment; this occurs in many Gram-positive and Gram-negative species. They are typically heat-labile, meaning heat can inactivate many of them. So the statement that correctly differentiates endotoxins from exotoxins is the one that describes endotoxin as released during cell lysis, being LPS, associated with Gram-negative bacteria, and heat-stable.

Endotoxins and exotoxins differ in what they are, where they come from, and how they’re released. Endotoxins are parts of the bacterial outer membrane, specifically lipopolysaccharide (LPS), found in Gram-negative bacteria. They are not secreted proteins; they’re released mainly when the bacteria lyse or shed membrane components. Because they’re a structural lipid–polysaccharide complex, endotoxins are heat-stable.

Exotoxins, on the other hand, are proteins produced inside bacteria and actively secreted into the surrounding environment; this occurs in many Gram-positive and Gram-negative species. They are typically heat-labile, meaning heat can inactivate many of them.

So the statement that correctly differentiates endotoxins from exotoxins is the one that describes endotoxin as released during cell lysis, being LPS, associated with Gram-negative bacteria, and heat-stable.