A difference between exotoxins and endotoxins is that endotoxins….. A. Are made of proteins Can be released when the cell dies B. Are susceptible to high temperatures C. Are present in both Gram (-) and Gram (+) D. Can be converted to toxoids
The correct answer and explanation is:
The correct answer is C. Can be released when the cell dies.
Endotoxins are components of the outer membrane of Gram-negative bacteria. They are part of the bacterial cell structure, specifically the lipopolysaccharide (LPS) molecules that make up the outer layer of the cell wall. Unlike exotoxins, which are actively secreted by bacteria, endotoxins are typically released only when the bacterial cell dies and breaks apart. This is because endotoxins are part of the cell’s outer membrane and are not secreted under normal living conditions.
Exotoxins, on the other hand, are proteins produced and secreted by both Gram-positive and Gram-negative bacteria. These toxins are actively released into the surrounding environment, where they can cause damage to host cells and tissues. Exotoxins can often be neutralized by antibodies or converted into toxoids (harmless forms of the toxin used in vaccines), which is not the case for endotoxins.
Another key distinction is their heat sensitivity. Exotoxins are typically more heat-sensitive and can be destroyed by high temperatures, while endotoxins are more stable at high temperatures.
Endotoxins are also present primarily in Gram-negative bacteria, as Gram-positive bacteria do not have the LPS structure in their cell walls. Therefore, option C correctly describes endotoxins because they are released upon the death of the bacterial cell, in contrast to exotoxins which are actively secreted during bacterial growth.
In summary, endotoxins are released when the bacterial cell dies and breaks apart, whereas exotoxins are secreted by living bacteria and are proteins that can be neutralized by vaccines.