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Comment by cubefox | Hacker News Reader

Yeah, from Wikipedia:

> An essential nutrient is a nutrient required for normal physiological function that cannot be synthesized in the body (...) The nutrients considered essential for humans comprise nine amino acids, two fatty acids, thirteen vitamins, fifteen minerals and choline.

While some of these can be synthesized by other animals, this is not the case of minerals like iodine. I believe only organic compounds can be synthesized by animals.

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Our bodies can synthesize several inorganic compounds, and other organisms can synthesize even more. There are biological sources of $H_{2}O$, $NH_{4}^{+}$, $NO$, $HCO_{3}^{−}$, $HPO_{4}^{2−}$, and (traditionally considered inorganic despite having carbon) $CO_{2}$. Iodine is an element, not a compound, and can only be synthesized through nuclear processes, not chemical ones.

What is this kind of notation from/based on? e.g $H_{2}O$

Looks like LaTeX syntax.

LaTeX would be $H_{2}O$ – or, more likely, \ce{H2O} or \ch{H2O}.

That's TeX. Every time Donald Knuth gets distracted from writing The Art of Computer Programming, he makes another piece of load-bearing infrastructure. (TeX came about because the second edition of Volume 1 didn't look as nice as the first edition.)

The definition I remember from my chemistry class is that organic compounds are those having at least one C-H bond.

It's a reasonable definition, especially when classifying biochemicals, but there are always edge cases.

For example : https://en.wikipedia.org/wiki/Carborane that definitely do have C-H bonds but are mostly B-B, B-C, B-H.

I feel your use of TeX (or whatever that notation is precisely ...) is far too clear.

Possibly use InChI instead, so instead of "$HPO_{4}^{2−}$", use "InChI=1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)/p-2". Or, more concisely, just use the key, which is "NBIIXXVUZAFLBC-UHFFFAOYSA-L". :)

(from : https://www.ebi.ac.uk/chebi/searchId.do?chebiId=43474)

Or just unicode. Standard digraphs ftw (xcompose, wincompose...). It's even typed in the same way (_4 ^+ etc) - and maybe there's tex tools that output unicode these days where possible?

H₂O, NH₄⁺, NO, HCO₃⁻, HPO₄²⁻

Yes, that's pretty good ... but - the charges on [NH4]+, [HCO3]-, and [HPO4]2- should be above the subscripts on their last atoms. Minor point really.

true, true... I wonder if that's even possible to do in unicode. maybe some combining char thing. I certainly wouldn't be able to type a digraph of it from memory if it is. But, I feel it's still more readable this way

Or Hacker News could finally add support for LaTeX and markdown...

Minerals (as the term is used in nutrition, not in mining) are chemical elements, not "compounds". They are part of the constituents that can be synthesised into compounds. Usually our bodies obtain them in some form of organic or inorganic salts, which are compounds, so we obtain them as parts of compounds. To synthesise compounds that contain iodine, you need iodine in some form. As we are not talking about nuclear reactions through which elements are synthesised through other elements, there is no way humans, animals or plants synthesise any minerals like iodine, we all obtain them from some source. The original sentence is weird, because it talks as if iodine can be synthesised somehow chemically but just our bodies are unable to.

Does respiration count as synthesis?

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