Biochemical experiments on living organisms more than once end up with massbalances that don't match. One of the most captivating explanations for this phenomenon has been formulated by the biotransmutation theory, which is more than just a scientific theory.
Transmutation occurs where atomic nucleï transfer into other nucleï. The most wellknown form is that of nuclear decay. Biotransmutation has been defined as a nuclear conversion controlled by living cells. The most interesting articles describe the effects in agriculture (fertilization), nurishment along with health, and the environment. It is within these disciplines (and not so much in chemistry) that you may find articles on possible biotransmutation, a model that by all means should not be confused with such a thing as cold fusion.
The model has been postulated after an incident that took place in the nineteen fifties, when a French researcher, Louis Kervran, published his findings on cases of Carbon monoxide (CO) poisoning at a workshop where no atmospheric CO could be detected.
With no alternatives at hand the following idea emerged that the Nitrogen, that is abundantly present in the air, can be agitated on a hot Iron surface and, when inhaled interacts with longue tissue, can polarize into CO. And, not surprisingly, in a Argon/Oxygen environment the poisoning didn't occur.
This concept is a grave sin against the law of conservation of mass or energy, because the massdeficiencies don't seem to come out. But besides the fact that this does not seem to match the fysio-chemical theory, the biotransmutation theory provides a seemingly endless array of explanations for mysterious conversions.
One of the most peculiar paradoxes of this theory surely is, that in living nature it can sometimes be better to not replenish obvious deficiencies of certain substances. Who would think of treating Iron-anaemia with Manganese? And who would take into account, that replenishing a life threatening deficiency of Potassium in blood would cause an immediate death?
The reaction-equations are simple. The difference between Iron (Fe) and Manganese (Mn), Sodium (Na) and Magnesium (Mg) or between Potassium (K) and Calcium (Ca) is Hydrogen (H). The difference between Sodium and Potassium (or between Magnesium and Calcium) is Oxygen (O). In this way a aerobe organism can control the energyflow with Na/K, for example from blood (high K) towards cells (high Na). There are even names for the enzymes involved. The acidity can be controlled with Na/Mg or K/Ca. These four vital elements make up the engine of most living creatures. There are more exotic cases. For example Tillandsia (Spanish Moss) that grows on copper wires and when analyzed proofs to contain over 10% of Ironoxide. The Manganobacter controls it's acidity using Mn/Fe. Some elements are not usefull to be converted as reserve or something you need.
What if your massbalance for a given element is completely wrong? Well, you make up balances for a number of elementpairs, known from the biotransmutation theory. With a bit of luck the massbalance for the calculated elements will match.
Long time ago a substance was taken from the market. This substance supposedly made bones stronger but did not contain Calcium. (The Ca source proofed to be organically bound Silica; The Ca source voor sea animals depends on the watertemperature, but it usually is Magnesium.)
A nice method for checking the proposed conversions is measuring the isotope composition of 'living' elements and that of 'dead' elements. Some isotopes cannot be converted because there is no stabel counterpart in the elementpair. For that reason finding out the role of a giving element using a (radioactive) isotope is not allways equally succesfull. There even seems to exist an organism that can rapidly break down a radioactive Hydrargyrum isotope.
There is plenty of literature on this subject. One of the (Russian) articles contains a search for the abovementioned mister Kervran: He can not be found (anymore). One nice paperback is called `The Secret Life of Plants`.