Text: Select characteristics exhibited by exotoxins, but not exhibited by endotoxins Check All That Apply – Composed of lipopolysaccharide – Require very small doses to cause toxic effects – Secreted from living cells – Heat stable
The Correct Answer and Explanation is:
The correct characteristics that are exhibited by exotoxins, but not by endotoxins, are:
- Require very small doses to cause toxic effects
- Secreted from living cells
Explanation:
Exotoxins and endotoxins are both types of toxins produced by bacteria, but they have distinct properties.
Exotoxins:
- Require very small doses to cause toxic effects: Exotoxins are highly potent and can cause damage at very low concentrations. For example, botulinum toxin, produced by Clostridium botulinum, is one of the most potent exotoxins known.
- Secreted from living cells: Exotoxins are actively secreted by living bacterial cells. These toxins can be released into the surrounding environment, often affecting host tissues and causing diseases like diphtheria, cholera, and tetanus.
Endotoxins:
- Composed of lipopolysaccharide (LPS): This is a characteristic unique to endotoxins, not exotoxins. Endotoxins are part of the outer membrane of Gram-negative bacteria, and their toxic effects are usually released when the bacteria die and the cell wall breaks apart.
- Heat stable: Endotoxins are heat-stable, meaning they can withstand higher temperatures without losing their toxic properties. This stability can make endotoxins harder to neutralize during medical treatments like autoclaving.
Summary:
Exotoxins are potent proteins secreted by bacteria that cause harm at low doses, whereas endotoxins are lipopolysaccharide components of the outer membrane of Gram-negative bacteria that are only released when the bacteria die. Exotoxins are secreted actively by living cells, whereas endotoxins remain part of the bacterial cell wall until bacterial death.
