Toxin
A
toxin (
Gk. toxikon "(poison) for use on arrows,") is a
poisonous substance produced by living cells or organisms. Toxins are nearly always
proteins that are capable of causing disease on contact or absorption with
body tissues by interacting with biological
macromolecules such as
enzymes or
cellular receptors. Toxins vary greatly in their severity, ranging from usually minor and acute (as in a
bee sting) to almost immediately deadly (as in
botulinum toxin).
Biotoxins vary greatly in purpose and mechanism, and can be highly complex (the venom of the
cone snail contains dozens of small
proteins, each targeting a specific nerve channel or receptor), or relatively small protein.
Biotoxins in nature have two primary functions:
*Predation (
spider,
snake,
jellyfish,
wasp)
*Defense (
poison dart frog,
deadly nightshade,
honeybee, wasp)
Some of the more well known types of biotoxins include:
*
Hemotoxins target and destroy red blood cells, and are transmitted through the bloodstream. Organisms that possess hemotoxins include:
**Pit vipers, such as
rattlesnakes.
*
Necrotoxins cause necrosis (i.e., death) in the cells they encounter and destroy all types of
tissue. Necrotoxins spread through the bloodstream, but infect all tissues. In humans,
skin and
muscle tissues are most sensitive to necrotoxins. Organisms that possess necrotoxins include:
**The
brown recluse or "fiddle back" spider.
**
Necrotizing fasciitis (the "flesh eating"
bacteria)
*
Neurotoxins primarily affect the nervous systems of animals. Organisms that possess neurotoxins include:
**The
Black Widow and other
widow spiders.
**The
box jellyfish.
**
Elapid snakes.
**The
Cone Snail.
When toxins are generated by
bacteria, they are called
toxoids. These toxins are metabolism byproducts and may be produced either in the living body during
infection (for instance, by
tetanus) or by bacteria in dead biological material.
In the context of
complementary medicine the term is often used as a broader category of any harmful substance claimed to cause ill health, though mainstream scientists argue that the nature of such substances is usually unproven. Many non-technical and lifestyle journalists also follow this usage to refer to
toxic substances in general, though some specialist journalists at publishers such as
BBC and
The Guardian maintain the distinction that toxins are only those produced by living organisms.
When used non-technically, the term "toxin" is often applied to any
toxic substances. Toxic substances not of biological origin are more properly termed
poisons.
Practitioners of
alternative medicine often apply the term in a non-specific manner to refer to a broad category of harmful substances claimed to cause ill health.
*
Apitoxin*
Hemotoxin*
Neurotoxin*
Phototoxin*
List of fictional toxins*
Most Common Household Toxins*
Society of Toxicology*
Cycad toxicity*
Corrections and clarifications,
The Guardian, 30 May, 2005.
