Hi everyone, long time reader first time poster.
I do a bit of research on the origin of life, some papers on this discuss carbon concentrations in various scenarios and the need for a mechanism of concentration. But I have been unable to find a single one which relates it to the carbon concentration in living cells and thus the degree of concentration required. I thought it might be the kinda thing you guys would be interested in. Any thoughts?
What kind of carbon are you talking about? Since we’re organic beings, virtually every non-water molecule in our body has carbon.
I’m talking about elemental carbon, not carbon molecules but C itself, i hear stats like the body is ~70% water so what remaining % is hydrogen, oxygen, nitrogen, phosphorous and most importantly carbon?
That 70% water is about 89% O and 11% H. That means O makes up at least 62% of the body (there is a lot of O in the other 30% of the body as well).
Added on preview: (derived from Squink’s link) O is ~61%, C is ~23%. I think this is wrong, unless water makes up quite a bit less than 70% of the body.
Your point is essentially correct, QtM, and I expect it will lend insight to many who never thought in those terms
My pedantic side does impel me to remind you of the ca 5 lbs of stoichiometric variants of hydroxyapatite [roughly Ca[sub]10/sub[sub]6/sub2] in the bones of a typical 170lb male. (I’m just trying to avoid someone overgeneralizing your remark, and turning it to a new Internet factoid we’d have to slay later)
Yeah, I realize that it’s an ionic compound, so the nature of the “molecule” is a bit fuzzy, but if we limit ourselves to covalent compounds, where individual molecules are easily delimited, then “virtually all the non-water molecules contain carbon” would apply to a lot of things – like soda pop.
BTW, you are my hero.
To the OP, I’m not quite sure what kind of concentration figures you are looking for. However, the elemental composition of the “170 lb male” (beloved by med school professors) includes ~35lbs carbon (second only to oxygen at ~95lbs). A sizeable percentage of that is in the form of extracellular protein matrix, stored fat, and specialized structures (e.g. a sizeable fraction of our biomass is muscle, whose specialized proteins (mostly actin and myosin) give it a a much higher protein [and hence carbon] content than a bacterial cell)
Therefore, while the human body may have a 20% “carbon concentration” overall, I think a “generic human cell” could reasonably have 5-10% and as little as 1-2% seems very reasonable for a primitive protocell. I wouldn’t be surprised if it could work with much less (0.1%? 0.01%?), but since we are talking about a biochemistry that would be significantly different from the mainstream of modern cells (and we don’t even know the limits for cells with our current primary pathways) I can only speculate.
While I do believe that the earliest protocells would have been more “dilute” (if only because of the lack of sophisticate osmotic control mechanisms), it’s important to note that our current oxygen-rich atmosphere is a bio-artifact (Free oxygen was once a highly toxic waste product, and is still toxic to many bacteria – in fact, reactive free oxygen species are used by some of our defensive cells as a primary weapon against prokaryotic invaders.) The prebiotic atmosphere would have been rich in compounds like methane, carbon dioxide, carbon monoxide (and non carbon-compounds like nitrogen) It’s quite probable that the very “air” contained a on the order of 10% carbon, making such concentrations much easier to achieve in prebiotic solutions world wide than today.
Much of the ancient atmopheric carbon has been scavenged, esp. in the post-oxygen era, and now resides in geological carbonate deposits of biological origin.
We used to do exercises in “life building” in some of my mol bio courses.
[lame after-the-fact rationalization] Oh, I knew that, but just assumed that the ionic form of hydroxyapatite would be in equilibrium with some organic compound or other[/lame rationalization]
it’s the zymolosely polydactile tongue, right? Or the xmex-like snout?