If we evolved in the ocean, why do we have more K than Na in our biochemistry?

I really have no answer, nor even a clue really, about this question.

I was looking at something else entirely and it just jumped out at me.

The ocean is mostly NaCl so very sodium rich. Our bodies (and plants and…) are very potassium (K) rich.

One would expect that life, evolving in a primitive ocean, would have evolved in balance with the natural mineral levels in that ocean. So what is with the high K level in cytoplasm? Hmmm?

We do know that sodium chloride levels in the ocean are higher now than when fish evolved, as many fish species have active sodium chloride transport systems to keep their overall salinity in balance, so one can guess that over all of the duration of life sodium levels have risen. So was the ancient sea potassium rich? Or not? What do the oldest ocean sediments say, if anything?

Or was this the only way complex life could work, making voltage across nerve cell walls being important to us, bacteria not so much?

Somehow it just seems wrong. We ought to be more sodium tolerant.

OK, some kicking around gives a few interesting links, but nothing that seems to answer the question of “why so much potassium”. Then again, I didn’t “dig here!” much. Just enough to get frustrated at all the OTHER things it leads to…

These folks look at bacterial composition, but ignore K vs Na near as I can tell:

Click to access a010p015.pdf

This article inspects the sodium potassium pump, finding it necessary for nerves to function and with high K inside and high Na outside the cell, but doesn’t bother to ask about the overall high need for K in life:

Since the plasma membrane of the neuron is highly permeable to K+ and slightly permeable to Na+, and since neither of these ions is in a state of equilibrium (Na+ being at higher concentration outside the cell than inside and K+ at higher concentration inside the cell), then a natural occurrence should be the diffusion of both ions down their electrochemical gradients—K+ out of the cell and Na+ into the cell. However, the concentrations of these ions are maintained at constant disequilibrium, indicating that there is a compensatory mechanism moving Na+ outward against its concentration gradient and K+ inward. This mechanism is the sodium-potassium pump.

We spend a lot of energy on Na pumping:


The Na+-K+-ATPase is a highly-conserved integral membrane protein that is expressed in virtually all cells of higher organisms. As one measure of their importance, it has been estimated that roughly 25% of all cytoplasmic ATP is hydrolyzed by sodium pumps in resting humans. In nerve cells, approximately 70% of the ATP is consumed to fuel sodium pumps.

Physiologic and Pathologic Significance

The ionic transport conducted by sodium pumps creates both an electrical and chemical gradient across the plasma membrane. This is critical not only for that cell but, in many cases, for directional fluid and electrolyte movement across epithelial sheets. Some key examples include:

The cell’s resting membrane potential is a manifestation of the electrical gradient, and the gradient is the basis for excitability in nerve and muscle cells.
Export of sodium from the cell provides the driving force for several facilitated transporters, which import glucose, amino acids and other nutrients into the cell.
Translocation of sodium from one side of an epithelium to the other side creates an osmostic gradient that drives absorption of water. Important instances of this phenomenon can be found in the absorption of water from the lumen of the small intestine and in the kidney.
Depending on cell type, there are between 800,000 and 30 million pumps on the surface of cells. They may be distributed fairly evenly, or clustered in certain membrane domains, as in the basolateral membranes of polarized epithelial cells in the kidney and intestine.

Clearly it is very important to “virtually all cells of higher organisms”. Though that just makes me wish for a similar look at ‘lower organisms’… IFF we find that bacteria are closer to seawater Na/K ratio, the question changes to ‘why is higher life’ this way…

but my search-foo was not working well on bacterial Na/K cytoplasm ratios… so I’m taking a break from that search series while I reconsider search words.

The Wiki says we have 2.5 x 10^-3 potassium mass fraction and 1.5 x 10^-3 sodium. Yet sea water is 1.08% sodium and only 0.04% Potassium.

So why do we end up with about a 1.6 : 1 ratio of K : Na while sea water has a 0.037 : 1 ratio?

Something just seems terribly strange about that…

Perhaps K is much more concentrated near Black Smokers, or in primordial mud, or wherever life started. It seems like a clue to something, but I can’t see “what?”… Maybe it’s time to swap over from tea to wine and move from analytical to insightful ;-)

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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21 Responses to If we evolved in the ocean, why do we have more K than Na in our biochemistry?

  1. Larry Ledwick says:

    Just wondering if the other thing you were investigating was hydration therapy fluid mixtures, where they get osmotic balance by adding sugar to the salts to improve absorption?


  2. sabretoothed says:

    Click to access 6045.full.pdf


    Life started underground, most of it is actually there, we are the freaks. As there is at least 4km deep life all around the planet, this is more area than the surface area of earth. Life most likely come from somewhere else, started underground and we are the odd ones, most of earth’s life is actually underground powered by geothermal energy and feeding on oil.

  3. omanuel says:

    Deep-seated life is important and merits more consideration.

    I knew Tommy Gold personally and admired his independent spirit during the days of the Apollo program.

    But, Tommy ignored overwhelming evidence Earth accreted in layers (heterogeneously) out of poorly mixed supernova debris orbiting the pulsar that remained at the center of the solar system and became today’s Sun.

    While I have your attention, E.M. Smith, I would like to recommend another blog site i recently found:

    Michael Krieger’s Liberty Blitzkrieg:


  4. tom0mason says:

    You may find this of interest http://www.usa-journals.com/wp-content/uploads/2014/03/Mohammed_Vol-23.pdf
    This paper discusses serum levels in lungfish of total protein, albumin, globulin, urea, uric acid, sodium and potasium. Much of the paper talks about the way ammonia is excreted by aquatic life (in the main), and as lungfish ( and also amphibians) move to the land there bodies respond by making urea and uric acid as the waste product.

    There is another paper ($40!) at http://link.springer.com/article/10.1007/s00360-014-0809-0
    that appears to go into the Na/K changes in the lungfish brain ‘during the induction, maintenance and arousal phases of aestivation in air.’

    From the little I’ve looked at there seems to be a fair amount of studies done on lungfish and amphibians with reference to metabolic changes, on moving from water to land, in nitrogen use and removal, and the changes in Na/K balances.

    Hope this is some help.

  5. E.M.Smith says:

    Looks like bacteria have sodium pumps too, so it is a very very old structure and has been important ‘from the early days’…


    Bacterial sodium ion-coupled energetics.
    Dimroth P1.
    Author information
    For many bacteria Na+ bioenergetics is important as a link between exergonic and endergonic reactions in the membrane. This article focusses on two primary Na+ pumps in bacteria, the Na(+)-translocating oxaloacetate decarboxylase of Klebsiella pneumoniae and the Na(+)-translocating F1Fo ATPase of Propionigenium modestum. Oxaloacetate decarboxylase is an essential enzyme of the citrate fermentation pathway and has the additional function to conserve the free energy of decarboxylation by conversion into a Na+ gradient.

    Many of them using light to drive the pump… Gee, solar powered bacterial pumps, who knew?


    Abstract• Accession codes• References• Author information• Supplementary information
    Light-driven proton-pumping rhodopsins are widely distributed in many microorganisms. They convert sunlight energy into proton gradients that serve as energy source of the cell. Here we report a new functional class of a microbial rhodopsin, a light-driven sodium ion pump. We discover that the marine flavobacterium Krokinobacter eikastus possesses two rhodopsins, the first, KR1, being a prototypical proton pump, while the second, KR2, pumps sodium ions outward. Rhodopsin KR2 can also pump lithium ions, but converts to a proton pump when presented with potassium chloride or salts of larger cations. These data indicate that KR2 is a compatible sodium ion–proton pump, and spectroscopic analysis showed it binds sodium ions in its extracellular domain. These findings suggest that light-driven sodium pumps may be as important in situ as their proton-pumping counterparts.

    So I was leaning toward that Gold ‘deep biosphere’ idea as rocks have lots of K in them, then it seems that light driven pumping is also important, so where’s the light? On the surface….

    Yeah, no allowance for a few billion years of mutation. Light driven might have evolved from chemical driven. Dual paths (surface, in the dirt and rocks) are possible. Etc. etc…

    But clearly K vs Na pumping is important to most life (along with proton pumps, it wold seem) and life likes more K and less Na than in sea water. It also likes light for some pumps.

    Curiouser and curiouser…

    @Larry Ledwick:

    Had not been looking at it, but interesting just the same. ( I’d been wondering why we use table salt, but not KCl on food, yet KCl is used by folks with blood pressure issues, and figured it would have to do with blood NaCl levels vs the ocean, and found a surprise…)


    I’d forgotten that Gold was not just about oil, but about the origin of life too… Thanks for the reminder. High K level in some rocks would be an explanation. Wonder what the K / Na ratio is in deep brines in oil wells…

    Click to access brines.pdf

    claims that they tend to come from sea water (with various evaporations) and has an interesting chart on page 29. Halite precipitates / crystallizes out leaving a very K rich brine, then the K salts precipitate. I wonder if life formed in brine pools… ( but we have too much water for that… so maybe brine isolates that then rehydrated?… even curiouser… )


    Interesting link. Eclectic interests…


    Oh boy, more reading ;-)

  6. p.g.sharrow says:

    I would rather doubt that Archean life could originate in the ocean or in surface brine pools. The most likely place would be where deep magmatic fluids were percolating up with hydrocarbons. That sodium / potassium balance would indicate saphonation and the creation of ionic imbalance being created by flow.
    The very early surface conditions would be too diluted, harsh and unstable for “life” beginnings to start. Once started, life could then colonize other conditions. Our oxygen based life is the result of life adapting to the creation of surface conditions of a heavily oxygen polluted atmosphere. We have fairly well demonstrated that hydrocarbons were part of the planet formation material as well are created in the mantel. The break down of metal sulfides are the energy source utilized by deep Archean organisms, no sunlight needed. In fact sunlight quickly destroys unprotected simple life. pg

  7. H.R. says:

    p.g. sez:
    ” In fact sunlight quickly destroys unprotected simple life. pg”
    Dang! That’s something “everybody knows” yet it has to hit you in the right context. Excellent support for your points. Thanks!

  8. Larry Ledwick says:

    That also raises some other interesting questions, during the time that early life began to flourish was the sky more like Venus with sufficient persistent cloud cover to prevent problems with UV killing organisms or had the atmosphere cleared enough to resemble current conditions?

    Also how strong was solar UV back then?
    Was the water constantly tubid so that little UV got below the surface?

    There might have been very different illumination conditions, or life originated just below the optical extinction depth for UV in near shore environments but not in shallow water.

    Just because early life would be killed in modern shallow pools does not necessarily mean the same problem existed when early life formed.

    There are areas in the modern tropics that almost never see a clear day with heavy fog or overcast much of the time.

  9. E.M.Smith says:

    My personal favorite guess for the origin point of life was near Black Smokers in the abyssal depths. With the ‘nozzle’ pointed up, you get cycling of water next to them. Cold / hot / cold cycles can happen many times / hour along with solution gradients and energy rich mineral. I could see that, with the turbulence, rapidly leading to chemical complexity along with formation of bubbles ( “membranes”) in the soup. Add that modern PCR replicates DNA with a heat / cool / heat / cool cycle and…

    Just always looked like the right mix of things.


    IFF the primordial ocean was like now, then we ought to have a tolerance for high sodium inside cells. We don’t, it’s high potassium. So something is out of kilter.

    Perhaps the early ocean was not yet sodium rich, or life formed in a semi-submerged area near a smoker where the halite had already precipitated out ( Iceland like, anyone?) or who knows what.

    It’s just a big dig here…

  10. omanuel says:

    Did plant life use photosynthesis to convert an early CO2-polluted atmosphere into an O2-polluted atmosphere? Did animal life then arise, using atmospheric O2 to oxidize and release “stored sun-light” in foods?

  11. E.M.Smith says:


    Close. It was a blue-green algae that made the world oxygen rich. So more like “A plant”… (which also raises the question that if the early world was so CO2 dominated, why didn’t it overheat and burn up ;-)


    They are often called blue-green algae, but some consider that name a misnomer, as cyanobacteria are prokaryotic and algae should be eukaryotic, although other definitions of algae encompass prokaryotic organisms.

    So it’s a little unclear if they were “plants” in the modern sense, or just some kind of bacteria…

  12. omanuel says:

    @E.M. Smith

    Why didn’t the Earth’s early CO2-rich atmosphere overheat and burn up?

    It is difficult to believe claims that CO2 – the gas that allows animals and plants to live together on Earth – CO2,
    _ 1. A waste product of animal life
    _ 2. An essential food of plant life . . .
    is a dangerous air pollutant that will overheat Earth’s atmosphere . . .

    after scientists manipulated, hid or ignored experimental data for seven decades (1945-2015) that showed Earth orbits 1 AU (astronomical unit) from the pulsar that made our elements, birthed the solar system, sustained the origin and evolution of life, remains in contact with every atom, life and world in the solar system . . .

    and controls the climate of the entire solar system, a volume of space that is now greater than the volume of 10,000,000,000,000,000,000 Earth’s!

  13. Jason Calley says:

    Well, sure there is more sodium than potassium in earth’s ocean water — but the balance was different in the oceans of Zebulon Gamma 247 where life originated.

    (I might be kidding. I am not sure.)

  14. p.g.sharrow says:

    An interesting article on gold deposits
    It is known certain bacteria gather gold from solution and “plate” themselves. This creates nodules of gold where there is no float from upper igneous deposits. A friend of mine discovered a dry valley in eastern Nevada with such a deposit.
    For those that don’t know, Archean bacterias often metabolize hydrogen sulfide or metal sulfides for
    energy. They likely existed long before sunlight and sugar organisms evolved. This sulfide fueled life is the most wide spread and abundant life on the planet pg

  15. omanuel says:

    @ p.g. sharrow

    Intriguing! The heaviest calcogen element, Tellirium, is a good tracer for gold deposits.

  16. sabretoothed says:

    Paul Davies has similar ideas too, he thinks life came from outside the solar system and is probably also on Mars, just have to dig deeper down :)


    It makes sense though, ever time life gets completely wiped out it comes out again from the underground again

    There are really strange life forms deep down, worms, bacteria lots of weird stuff and some is 4km deep


    No need to evolve, as in perfect location ;) http://www.newscientist.com/article/dn26742-deep-bacteria-may-evolve-even-without-passing-genes-on.html


    Some live on radioactivity, others live on oil http://www.nsf.gov/news/special_reports/microbes/Xtreme_microbes_radiation_summ.pdf

    So maybe all the fossils of oil are really just from the bacteria, not really squashed trees and fish ;)

    Or already there, since titan has a sea, but the hydrocarbons are eaten by the bacteria that seeded the planet.

  17. Jason Calley says:

    @ sabretoothed “Some live on radioactivity, others live on oil”

    We even have surface dwelling macroscopic forms that metabolize gamma rays — black fungus growing inside the reactor at Chernobyl.

    According to the wiki, the ability to metabolize gamma rays seems to use melanin. I suspect that radiosynthesis may be more common that we think. IIRC the University of Wisconsin and the US Navy did a study of wound healing rates when the wounds were illuminated with red and infrared light twice a day. Result? Quicker healing, about 2/3 normal time. Life is adaptable — perhaps we have abilities we do not suspect.

  18. Roderic L. Olsen says:

    A very interesting question that you have raised. Might it have something to do with maintaining a largely structured form of water near cell protein surfaces inside the cell? See Dr. Gerald Pollack’s book “Cells, Gels, and the Engines of Life”, and my review of it at http://www.amazon.com/review/R3DQE7167KRDY5

    Also have a look at http://www.drlwilson.com/articles/SODIUM-POT%20RATIO.HTM

  19. Roy says:

    This is my PhD question, have a theory, hope to publish soon.

  20. E.M.Smith says:


    Feel free to post your theory here when it is ready. I’d love to have more clue on this.

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