Which describes exotoxins?
A The symptoms are specific for each one
B None of these describes exotoxins
C They can’t be inactivated
D They are found in the cell walls of gram-negative bacteria
E They are lipopolysaccharide
The correct answer and explanation is:
The correct answer is A. The symptoms are specific for each one.
Exotoxins are potent, soluble proteins produced by both Gram-positive and Gram-negative bacteria, which can cause specific symptoms depending on the type of toxin and the tissue or organ affected. These toxins are often secreted into the surrounding environment during bacterial growth. Unlike endotoxins, which are part of the outer membrane of Gram-negative bacteria and are released only when the bacteria die, exotoxins are released actively during bacterial metabolism.
The symptoms caused by exotoxins vary widely depending on the specific toxin. For example, botulinum toxin causes paralysis by inhibiting the release of acetylcholine at neuromuscular junctions, leading to respiratory failure. On the other hand, diphtheria toxin interferes with protein synthesis in cells, leading to tissue damage in the throat and potential systemic effects. Thus, the effects and symptoms can be unique to each toxin and its target tissue.
Why the other options are incorrect:
- B. None of these describes exotoxins: This is incorrect because option A correctly describes exotoxins.
- C. They can’t be inactivated: This is false. Exotoxins can often be inactivated by heat or chemicals, a process known as detoxification. This is how vaccines like the diphtheria and tetanus vaccines are made, using inactivated toxins.
- D. They are found in the cell walls of gram-negative bacteria: This refers to endotoxins, not exotoxins. Endotoxins are part of the cell wall of Gram-negative bacteria and are released when the bacteria die or are damaged.
- E. They are lipopolysaccharide: This describes endotoxins, not exotoxins. Exotoxins are proteins, while endotoxins are lipid and polysaccharide complexes found in the outer membrane of Gram-negative bacteria.
Exotoxins are potent and can cause a range of symptoms specific to their target tissues, which is why vaccines targeting them are so crucial in preventing bacterial diseases.