Human chemistry

I was wondering, what elements is the human body composed of? If possible, how do scientist figure out what the proportions that comprise of the the human body?

Scientists figure it out by searching Wikipedia. Answer: mostly hydrogen, carbon, and oxygen.

SPONCH - sulfur, potassium, oxygen, nitrogen, carbon, hydrogen.

Isn’t the “P” in that phosphorus, not potassium? Still, there are a number of trace elements in the body, too, including potassium, iron, sodium, chlorine, and zinc, off the top of my head.

Phosphorus, certainly, but actually there will be quite a lot of potassium and sodium, also chlorine, not just traces. There are plenty of inorganic ions in the body, largely, but not exclusively, Na+, K+, Cl- and SO4–, apart from all the organic stuff (which is mostly C,H,O,N, S & P). Nobody seems to have mentioned calcium yet either. Bones are largely calcium phosphate, and there are plenty of calcium ions, Ca++, elsewhere too. There will also be a fair amount of iron, particularly, but not only, in the hemoglobin of red blood cells, and magnesium (mostly as inorganic Mg++ ions again).

After that you can perhaps begin talking about trace elements (unless I have forgotten something). Off the top of my head, we need (in fairly small amounts), zinc, selenium, copper, cobalt and iodine.

There may well be more necessary trace elements that I either do not know about or have forgotten. However, I suspect that quite a few of those on the Wikipedia list linked above are not actually necessary for life or health. For instance, bromine and fluorine are chemically quite similar to chlorine, and no doubt comprise some of the negative ions in the body, but if all of the bromide and fluoride ions were replaced chloride, I doubt it would do you any harm (though the reverse is certainly not true). Similarly, strontium is chemically quite similar to calcium, and and a certain amount of strontium gets into bone instead of calcium, but I doubt if any harm (and perhaps some good) would result if there were no strontium at all.

Some of the other elements listed are probably just, essentially, dirt: stuff that tends to get into bodies in small amounts, but has no real function.

You take a body and cook it down to ashes. Capture all the water boiled off, and do simple sepreations to find out what the ashes are made of.

Yep. Brian fart.

Then he should say “Excuse me.”

Good hell. I don’t know what’s wrong with me lately. I’m going to go ahead and blame it on my 6 week old daughter.

Sounds like a good excuse to me (six-week-olds, from what I understand, are composed primarily of poop, pee, and barf).

And while there is a decent amount of potassium, it’s not nearly as fundamental as phosphorus. Phosphorus is an ingredient in both DNA, the code of life, and ATP, its direct energy source, and thus plays multiple vital roles in all living things. Potassium, from what I understand, is primarily important in transmission of nerve impulses, and is therefore relevant only for animals (and not even all animals).

If you’re asking this to perform human transmutation, you’re better off forgetting about it. I know this guy who tried it once- totally became a double amputee.

Potassium (and sodium, calcium, and other inorganic ions) are not parts of biological macromolecules as phosphorus often is (not only do DNA, RNA and ATP contain phosphorus - cell membranes are largely made of phospholipids, and many proteins are phosphorylated too). However, the inorganic ions are just as essential to life, and not just to nerve transmission. Every living cell (human or otherwise) contains water with inorganic salts dissolved in it, and these have to be the right salts in the right ratios in the right places or else none of the macromolecular biochemistry will work properly. Furthermore, a multicellular body like a human one also contains a lot of extracellular fluids (blood, lymph, etc. etc.), which are also water which needs the right salts dissolved in it. Intracellular fluid (in all known organisms, I believe) has a relatively high concentration of potassium ions, and lower sodium and extracellular fluids are generally the reverse. (For a single celled organism in the sea, you can think of the sodium rich seawater as the extracellular fluid. Land dwelling multicellular organisms such as ourselves in effect carry their own bit of the ocean within them, as extracellular fluid to bathe the cells.) Cells devote a lot of energy to maintaining things this way, pumping out excess sodium (though you do want some inside the cell) and taking in potassium. These inorganic ions (and the water in which they are dissolved) are every bit as essential and fundamental to life, all life, as are the components of macromolecules.

I had a high school chemistry text that said in a little “info box” that if the human body were reduced to its constituent elements, it would have a market value of something like $8.50 (give or take). This would have been with mid-1990s values for those elements.

Why does stuff like that rattle around in my brain (or my Brian), but I can’t remember where I put my keys 10 minutes ago?

I think that that’s one of those factoids that textbooks just copy straight from other textbooks without worrying about whether it’s true.

That would have to be true, because obviously, people from different countries would have to have different values, based on the current exchange rate. For example, with the incredible inflation they have these days in Zimbabwe, you would have to have a few million Zimbabweans in order to trade for, say a single Belgian. Commodity traders would make big money, that way, by buying Belgians for $8.50, or whatever the equivalent in Euros is, trading them for Zimbabweans, rendering them into their constituent elements, and selling those elements on the market. They would then use the profits to buy more Belgians, and start the process all over.

Thirty plus years ago Carl Sagan, in an episode of his series Cosmos, took all the elements in their proper proportions and mixed them up in a big cauldron!

Needless to say he didn’t create a human…

The chemicals are cheap, but do you know what the cost is, if you were looking at buying a body for something other than the constitutional elements? Like enzymes? or the brain for neuroanatomy? etc.

Just in case anyone was interested, I did some rough searching on prices for the common elements (up to 1 gram in a 70 kg body as per wikipedia). Where I could easily find them I used prices per metric tonnes of unrefined/cheap variants/compounds.

[name, percent, $/kg, kg, total]

Oxygen 						65 	0.21	4.30E+001	9.03
Carbon (coal)					18 	0.15	1.60E+001	2.4
Hydrogen (liquid)				10 	2.7	7.00E+000	18.9
Nitrogen (2 x urea)				3 	0.5	1.80E+000	0.9
Calcium (dicalcium phosphate x 2)		1.5 	12	1.00E+000	12
Phosphorus (included in above)			1 	0	7.80E-001	0
Potassium (2x potas.humate)			0.25 	1	1.40E-001	0.14
Sulfur 						0.25 	0.07	1.40E-001	0.01
Sodium (2x NaCL)				0.15 	0.05	1.00E-001	0.01
Chlorine (included in above)			0.15 	0	9.50E-002	0
Magnesium 					0.05 	20	1.90E-002	0.38
Iron (scrap price)				0.006 	0.08	4.20E-003	0
Fluorine 					0.0037 	0.5	2.60E-003	0
Zinc (scrap)					0.0032 	2	2.30E-003	0
Silicon 					0.002 	0.75	1.00E-003	0

Total price for a 70Kg body: $43.77, but I’m sure if you’re really buying in bulk some of the compounds would be a lot cheaper.

Well, as far as I know there’s no market for human brains. A neuroanatomist will get brain samples either directly from the hospital (after wrangling out research protocols, informed consent, and usually the patient’s death). Or they’ll get their samples from a brain bank run by various academic or government institutions. If the researcher pays anything, it’ll just enough to cover the costs of whoever provides it.

Enzymes run from very cheap to very expensive. Rennet, an enzyme used in cheese production, is extracted from cow stomachs. Since it’s essentially a by-product of producing meat, it costs just dollars per pound. At the other extreme, there are companies that produce small batches of high purity enzymes for use in research labs. Since there are a small number of well-funded labs that purchase these, they’re very expensive – I’ve seen prices as high as a few hundred dollars for what must be just a few micrograms. You could get a lot of these from humans, but it’d be very expensive to extract and purify anything useful.

Interesting research…thanks for that. Curious that two of the highest priced items on the list would be mostly bound up as water in the human body, and therefore much closer to worthless. Wonder what the cost of electricity to electrolyze a body’s worth of water would run. That might eliminate much of the cost of the raw elements…or maybe it wouldn’t if I’m underestimating the energy required.

Personally, if I had that shopping list, I’d just cheat. Get 50 liters of water and call it a day.