To: All Msg #231, Jun1693 12:24PM Subject: Seawater =/= blood, but. Sea water is not blood

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From: James G. Acker To: All Msg #231, Jun-16-93 12:24PM Subject: Seawater =/= blood, but... Organization: NASA Goddard Space Flight Center -- InterNetNews site From: jgacker@news.gsfc.nasa.gov (James G. Acker) Message-ID: <1vnvir$jb7@skates.gsfc.nasa.gov> Newsgroups: talk.origins Sea water is not blood. Well, that much should be obvious! Sea water is pure and clear, while blood has got all sorts of things in it -- red and white blood cells, platelets, proteins, hormones, waste products (urea, uric acid), etc. There really shouldn't be much of a similarity between an essentially biological fluid and a fluid that resulted primarily from inorganic chemical reactions. But, nonetheless, I attempted to compare the elemental chemistry of blood to the elemental chemistry of seawater. The numbers below are approximate: I couldn't compare the density of blood serum to seawater. The blood numbers are from Gould Medical Dictionary, Appendix, 3rd Edition, 1972 (what do you expect in an aerospace library?); the seawater numbers are from _Aquatic Chemistry_, 2nd Edition, Stumm and Morgan, available at fine marine science and hydrology graduate departments nationwide. Note that grams/kg is the most common method of expressing elemental concentrations in seawater, so I converted the blood numbers to this unit. Element SW (g/kg) Blood (g/kg) Bicarbonate .1424 .015 Calcium .4121 .05 (ionized) / .1 (serum) Chloride 19.354 3.6 Copper 10E-8 .001 (10E-3) Magnesium 1.29 .025 Phosphorus 2E-6 .0375 Potassium .399 .16 Sodium 10.77 3.2 Sulfate 2.712 .01 Order of concentration in SW: Cl, Na, Sulfate, Mg, Ca, K, bicarb. In blood: Cl, Na, K, Ca, Mg, bicarb, Sulfate. Also, SW pH range is from 7.4 - 8.2 (higher in surface waters), and blood is 7.38-7.44. So, what have we gained from this comparison?: Bicarbonate: in SW, controlled by carbon dioxide solubility and calcium carbonate saturation; in blood, controlled by respiration and gas exchange. Factor of 10 lower in blood. Calcium: Factor of 4-8 lower in blood. (Factor of 8 is derived from the "ionized" number.) Chloride: Approximate factor of 5 lower in blood. Copper: HUGE difference. Cu in seawater is controlled by mineral solubility and carbonate complexation; there's a lot of it in blood. Cu-hydroxyl complexes control solubility in SW. Mg: Factor of 50 less in blood compared to SW. P: Much higher in blood (required for metabolism in humans: energy source;) nutrient in SW. K: Factor of 2.5 less in blood compared to SW: used in muscles (I know this because K depletion can cause muscle cramps). Na: Factor of 3.3 less in blood compared to SW. Sulfate: Approx. 30 times more concentrated in SW. Now, if we just look at Na, Cl, K, Ca, Mg, and Sulfate, it's immediately apparent that Mg and sulfate are virtually non-existent in blood, but important SW constituents. Na, Cl, K, and Ca are (roughly) more dilute by factors of 3-8 in blood than in SW. More sodium may be required to balance the charge-balance problems due to the lack of Mg (Mg is a doubly-charged cation) in blood. Ca is slightly more dilute, but some Ca may be extracted for bone building (and Ca participates in some other biochemical functions as well.) Higher potassium levels (though I imagine these are fairly variable) might also compensate. Cu blew me away (I didn't bother comparing iron), but I didn't realize there was so much Cu in blood. So, seawater is clearly =/= blood. However, the similarity of some of the dilution factors (for Na, Cl, Ca, and K) is interesting. The absence of Mg and sulfate really intrigues me; if I was to postulate that blood serum was derived from SW, I'd first have to explain why Mg and sulfate were eliminated. For sulfate, it's suggestive that anaerobic processes rely on oxidation of sulfate to sulfides (in anoxic muds), so sulfate is less likely to appear in an oxic environment where respiration takes place. Mg is more troublesome. I can't think of any biochemical processes in humans that require Mg, so apparently we don't need it, and therefore it isn't present in high concentrations. Of course, we don't need chlorides either, other than to balance the charge! Comments welcomed! =========================================================== | James G. Acker Perspiring Writer | | jgacker@neptune.gsfc.nasa.gov Admirer of Swimwear | | | | "One mouse: two mice. One house: two hice. | | One goose: two geese. One moose: two meese. | | One die: two dice. One lie: two lice." | | Isn't English wonderful? | ===========================================================

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