I just found it so wild that our bodies are full of carbon and nitrogen (even if as part of other chemicals. We breath, what I assume, to be molecular nitrogen. But then slap a carbon atom to a nitrogen atom and you’re screwed. Why?
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* It comes down to two main things:
* The electrical charge on the molecule
* The shape of the molecule.
* When you combine two atoms into a molecule, the overall electrical charge changes and that has a big impact on what other molecules it reacts with.
* The same can be said for the new shape.
* The shape effects how those charges interact with other molecules making it either more or less reactive.
It’s precisely because it’s close but not quite the materials of our body that it’s a problem.
Like your body’s natural processes are bonding and reacting to things made up of C, H, N, O, etc.
Cyanide is disrupting a cellular process that turns carbon based molecules into cellular energy. When the carbon that has nitrogen on it enters that process, it blocks the process entirely, not just being incompatible, but shutting down that receptor to being able to engage in processing cellular energy. If that’s happening to cells in critical systems, then you are being poisoned.
Slapping that carbon on there creates an entirely different substance that behaves in an entirely different way compared to either of its constituent elements. A common similar example is table salt. Chlorine, highly toxic gas, and sodium, a hugely reactive metal… combine to make a white salt that we put on our food. Similarly, atomic nitrogen and atomic carbon are just meh. But, when they combine to make hydrogen cyanide, the resulting molecule like to bind with an iron atom on a particular enzyme in our bodies. When it does, it disrupts the metabolic pathway that depends on that enzyme, so that metabolic pathway breaks down, we lose the ability to extract energy from sugars, and we die.
TL;DR – chemistry
[DNA](https://en.wikipedia.org/wiki/DNA) also has carbon and nitrogen.
Cyanide is poisonous because it [blocks](https://en.wikipedia.org/wiki/Cytochrome_c_oxidase#Inhibition) your body’s ability to use oxygen to produce energy.
Sodium cyanide is very toxic, LD50 = ~8mg/kg
Methyl cyanide is about as toxic as table salt, LD50 = ~2000mg/kg
The lower toxicity is because methyl cyanide is metabolized slow enough that your kidneys can often remove most of it before it causes problems.
The danger of the CN- ion is that it is water soluble. Many potentially poisonous chemicals are oily and do not easily spread through the body. But even a few specks of potassium cyanide contain enough CN ions to get into every cell of the body. And the CN ion unfortunately looks very much like an oxygen molecules, electrically speaking.
Which brings up an interesting point- the reason we breathe oxygen in the first place. This is hard to make ELI5 but in a simple terms, Oxygen is greedy for electrons. It’s like a drain – the electrons trickle through the mitochondria in every cell , slowly doing work like a stream moving past a water wheel, and they end their journey by joining with the oxygen molecule. But every water wheel must have a place for the water to go. If the water could not flow away , it would pile up and the wheel would stop turning.
This is precisely what CN does. It sits where oxygen belongs and plugs up the channel. The electrons can no longer flow. This is equivalent to suffocation. Without oxygen there to accept the electrons, the mitochondria can no longer produce energy for the cell and the cell dies.
Cyanide inhibits the electron transport chain, preventing oxygen from being turned into water. We can just breathe out carbon dioxide, as long as we get enough oxygen. But our cells can only turn oxygen into water when they have enough glucose (or other sugars), which contains enough energy.
This is also why oxygen deprivation is so bad for your brain: your neurons burn a lot of glucose, and won’t stop until they get that sweet, sweet ATP.
For the same reason that chlorine and sodium combined are required for our body to function. Shape and charge are what it’s all about.
Well it’s the oxygen in Air we breath, not the nitrogen. Breathing pure nitrogen would kill you, due to lack of oxygen, though you wouldn’t realize it was killing you until it was too late.
Now wait until you think about how hydrogen combustes with oxygen to create water, which puts out fires.
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