VCDH Microbiology Practice Test

What is an endotoxin?

Actively secreted by bacteria Found in the nucleus of bacteria Endotoxin is produced by Gram-positive bacteria Released when Gram-negative bacteria die

Correct Answer:

Released when Gram-negative bacteria die

Explanation:

Endotoxins are part of the outer membrane of Gram-negative bacteria, specifically the Lipid A portion of lipopolysaccharide. They are not actively secreted by bacteria; they’re released when the bacteria die or their cell walls are disrupted, allowing the outer membrane to break apart and release endotoxin into the surrounding environment. This release can trigger strong immune responses, including fever and, in severe cases, septic shock. Gram-positive bacteria lack this outer membrane containing LPS, so they do not produce endotoxins in the same sense. Bacteria don’t have a nucleus, so endotoxin isn’t found in a nuclear location. Therefore, the statement that endotoxin is released when Gram-negative bacteria die captures the defining characteristic.

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