Tetrodotoxin: Structure & Mechanism

Instructor: Emily Cummins
This lesson goes over the structure of tetrodotoxin, which is a poisonous chemical found in the tissue and organs of a number of different fish and other sea creatures. We'll talk about it's chemical structure and how it works.

What Is Tetrodotoxin?

Small Puffer Fish
blow fish, puffer fish

Ever heard of a blowfish, also known as a puffer fish, the sea creature that puffs up to several times its size? If you ever find yourself face-to-face with a puffer fish, swim away as fast as you can! The potent neurotoxin tetrodotoxin, also known as TTX, is found in the liver and sex glands of these fish, and TTX is considered one of the most poisonous substances on earth!

Most tetrodotoxin poisonings occur when humans eat fish that has been improperly prepared. For example, eating piece of raw fish that contains tetrodotoxin can lead to poisoning. (As an aside, tetrodotoxin poisoning is very rare, so don't worry too much!) Because tetrodotoxin is a neurotoxin, or a chemical that affects the body's central nervous system, it is very dangerous. Ingesting this toxin can interfere with the brain's signals to other parts of your body, resulting in paralysis.

Structure of Tetrodotoxin

The chemical structure of tetrodotoxin looks like this if you were to write it out:


Now, this might look a little scary, but let's break it down. All this formula is saying is that tetrodotoxin is made of 11 Carbon atoms (C), 17 Hydrogen atoms (H), 3 Nitrogen atoms (N), and 8 Oxygen atoms (O). When these atoms come together in this combination, you have tetrodotoxin!

Now, when we write out formulas in chemistry it might look a little bit different than when a molecule comes together in real life. To see what we mean by this, take a look at the diagram that shows what tetrodotoxin looks like:

Structure of Tetrodotoxin
tetrodotoxin, pufferfish

See? The atoms group together in particular ways. We have 2 HO bonds, 2 OH bonds, 2 HN bonds, 1 CH2OH bond, 1 H2N bond, and the remaining oxygens and hydrogens are lone wolves, not bonded to anyone.

Mechanism of Tetrodotoxin

Talking about the mechanism of tetrodotoxin is another way of discussing how tetrodotoxin 'works.' As we mentioned before, tetrodotoxin is a neurotoxin, so we know that the primary chemical reaction is going to occur in the body's central nervous system. Tetrodotoxin works by blocking nerve impulses along your nerve fibers and your axons, which are nerve cells that send signals throughout the body. Primarily, tetrodotoxin blocks sodium channels in your body.

Sodium channels are important in your body because they help the flow of sodium ions, written out as Na+, which are important for conducting nerve impulses. You can think of sodium ions as electrical energy sources in your body. Nerve impulses are like your brain and body's way of communicating with one another. Tetrodotoxin is very effective at blocking sodium ion channels. When a sodium channel in your body is blocked, your nerve cells cannot be excited, which means signals cannot be conducted.

Tetrodotoxin is a much bigger compound than a sodium ion, so you can think of the reaction like this: when tetrodotoxin gets into your sodium channel, it's like a cork in a bottle. There's no room for the sodium ion to pass through.

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