For the past few weeks, we have been talking about the development of our understanding of the atom and, from there, our understanding of molecules.
I haven't provided citations to the literature - as a reader recently said I should - because most of this information is in the form of "common knowledge". It is something that every chemist and almost every scientist understands from an early point in their career.
Indeed, it is this common knowledge that gives science its strength and power in dealing with the world as we know it. The picture that science has developed of the world is incredibly robust and has withstood the tests of the past century.
For example, it is common knowledge that DNA carries the genetic coding that is used by cells to make proteins and subsequently other molecules. No serious scientist would question this. Not because they are afraid of asking troublesome question but because there is a tremendous amount of scientific weight behind that simple assertion.
Over the past 60 years, thousands of articles have demonstrated the role of DNA in the genetic code. We now have a very good understanding of just what the genetic code has to say. Biochemists can read genetic code in much the same way that the rest of us read a sentence and with about as much fluency.
But science has advanced beyond just reading the code. We know that errors in the transcription of DNA can give rise to various diseases such as cancer. But we also know that when we digest the DNA of other organisms, it is broken down into its constituent pieces. DNA doesn't get absorbed by the organism consuming it.
And even if it did, it can't get through the cellular membranes that protect the cell and the nucleus. DNA, by itself, is a pretty innocuous molecule.
This is why scientists have a fair degree of certainty that genetically modifying an organism is not likely to lead to disease or to cancer. A genetically modified string of DNA in a tomato will not withstand the rigours of the digestive system. Neither, for that matter, will the proteins generated by the genes on a string of DNA as will all of molecules from a genetically modified organism.
There is a saying: "You are what you eat" that often gets bandied about as a truism. It isn't. The molecules that you consume are broken down into their constituent parts once they hit the digestive system. This is the basis of digestion.
Membranes are lysed and the lipids can be absorbed but DNA is broken into its nucleotides prior to absorption. Similarly, proteins are broken down into their constituent amino acids. It is these pieces that we absorb in our digestive tracts and it is from these pieces that we build our molecules of DNA and protein.
But saying that "we are made from the broken down pieces of the things that we eat" just doesn't have the same ring to it.
That is not to say that everything that gets eaten gets broken down. Ionic compounds such as salt or NaCl simply dissociate in the digestive system. The sodium is absorbed by one receptor while the chloride goes a completely different route. And this is the important thing to recognize in dealing with ions. They act independent of any thing that they were once associated with.
If you swallow potassium or sodium carbonate, the carbonate ion is the same and does not stay associated with the cation at all. From a body's perspective, carbonate is carbonate regardless of the cation. Similarly, fluoride is fluoride regardless of the source. The ions know no providence.
Further, the same is true of molecular compounds. A sugar synthesized in a laboratory, grown in a plant, or harvested from a microbial organism can have exactly the same chemical makeup and constituents.
Indeed, the realization that organic compounds could be made in the laboratory and were identical to the chemical compounds found in natural sources was a major breakthrough in the 1800s. It provided both a method for identifying chemical compounds and verifying their composition as well as replacing limited natural sources.
There are many compounds that we now use regularly that were once sourced from organisms in our environment. Fortunately, we have synthetic methods for synthesizing them since demand in many cases would wipe out the natural source.
An example of this taxol, an anti-cancer medication obtained from the bark of the northwest yew tree. Without a synthetic version available from the lab, there wouldn't be enough to even conduct clinical trials let alone save millions of lives.
Yes, there are millions of chemical compounds in our bodies and in our environment. All made from atoms bonded together because, after all, what in the world isn't made of chemicals?
