Summary
Exotoxins are secreted proteins and endotoxins are lipopolysaccharide parts of Gram-negative walls that cause disease.
In depth
Exotoxins include botulinum, tetanus, diphtheria and cholera toxins, which are highly potent. Endotoxin (lipid A) causes fever and septic shock. Vaccines may use toxoids.
Toxin potency is measured as LD50. Anti-toxin antibodies are used therapeutically. Some toxins act on nerves, others lyse cells.
Key idea: toxins can cause symptoms even after the bacteria are gone.
Exotoxins are proteins secreted by bacteria, such as the AB toxins: B binds the receptor and A is the active part. Botulinum toxin blocks acetylcholine release (the most toxic substance known, with a lethal dose in the nanogram range per kilogram), tetanus toxin blocks inhibitory neurotransmitters, diphtheria toxin stops protein synthesis and cholera toxin permanently activates adenylyl cyclase causing massive fluid loss.
Superantigens from Staphylococcus and Streptococcus overstimulate T cells and cause toxic shock. Toxoids are inactivated toxins used in vaccines (tetanus, diphtheria), and antitoxins are used in treatment. Some toxins have medical use: Botox.
Common mistake: endotoxin is part of the Gram-negative outer membrane and is released on death, whereas exotoxins are secreted by living cells.
Frequently asked questions
What is Toxins?
Exotoxins are secreted proteins and endotoxins are lipopolysaccharide parts of Gram-negative walls that cause disease.
Which area of biology covers Toxins, and how advanced is it?
Toxins is one of the 54 topics in Microbiology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Protozoan Parasites, Gram Staining, Bacterial Cell Wall.
Can you give an example of Toxins?
Botulinum toxin is also used cosmetically (Botox).
What should I learn before Toxins?
Work through the Beginner topics in Microbiology first, such as Microorganisms, Bacteria, Archaea, then return to Toxins. Advanced topics assume the Intermediate vocabulary.
What topics are related to Toxins?
The closest topics to Toxins are Protozoan Parasites, Gram Staining, Bacterial Cell Wall, Bacterial Secretion Systems. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Toxins?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Toxins. To practise the whole of Microbiology, use the Microbiology quiz.
How is Toxins different from Protozoan Parasites?
Toxins: Exotoxins are secreted proteins and endotoxins are lipopolysaccharide parts of Gram-negative walls that cause disease. Protozoan Parasites: Single-celled eukaryotes such as Plasmodium and Trypanosoma that cause malaria and sleeping sickness. Read both side by side and note what each one explains.
What is a common mistake about Toxins?
Endotoxin is part of the Gram-negative outer membrane and is released on death, whereas exotoxins are secreted by living cells.
How should I study Toxins step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Protozoan Parasites and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.