toksin

Toksin is a poisonous substance produced by living organisms that can cause harm to other organisms. The term encompasses a broad range of molecules, from proteins produced by bacteria and plants to complex venoms. Toxins may serve ecological roles such as defense, predation, or competition, but they can also be byproducts of metabolism that become harmful in certain contexts. In scientific usage, toxins are often categorized by their source (biological, plant, fungal, or microbial) and by their mechanism of action (neurotoxins, hepatotoxins, cytotoxins, cardiotoxins, etc.).

Toksins are classified as endotoxins, which are cell-associated lipopolysaccharides released when bacteria die; and exotoxins, which are secreted proteins or peptides. Other important distinctions include venoms and toxins produced by exposure to fungi (mycotoxins), plants (phytotoxins), or animals (toxic compounds in venom).

Exposure routes include ingestion, inhalation, injection, or dermal contact. Mechanisms vary: some toxins inhibit enzymes, others disrupt membranes, interfere with nerve signaling, or damage DNA. The clinical effects range from local irritation to organ failure and death, depending on dose, route, and susceptibility.

Well-known examples include botulinum toxin and tetanus toxin from Clostridium species, ricin from the castor bean plant, aflatoxins from Aspergillus fungi, and animal venoms such as snake venom and cone snail toxins. In medicine, certain toxins are used in controlled doses for therapy, such as botulinum toxin in neuromuscular disorders and cosmetic uses.

Public health and medical management emphasize rapid identification, supportive care, and, where available, specific antitoxins or vaccines. Toxicology studies aim to determine lethal doses (LD50), mechanisms of action, and effective countermeasures. The term "toksin" is used in several languages as a direct translation of "toxin".