This article is a continuation of the series dedicated to empower students in explaining their study of Organic Chemistry to their parents and family members. Originally, I planned to publish this one on Thanksgiving, however I doubt many would be reading anything about Organic Chemistry that day. Hence you get an early treat (or trick). This is the only Organic Chemistry article I’ve written that comes with a disclaimer warning – read at your own risk! If you don’t want to learn something that will be permanently etched into your memory, then stop now! Otherwise, please let me spin a tale that relates your turkey sandwich (T-Day) to the amino acid glycine to oxygen transport in the blood to the amino acid tryptophan to happiness, sleep, the brain, olfactory perception, courtship and… an unexpected surprise!
As indicated in the previous “Organic Chemistry for Everyone” article, there are thousands of organic compounds. One group of organic compounds, known as alkaloids, contain electron rich nitrogen atoms. The study of alkaloids is part of the field of heterocyclic chemistry, a subdivision of Organic Chemistry. Alkaloids exist in plants and animals, so it shouldn’t be surprising they’re present in abundance in food.
Your turkey sandwich is rich in proteins, and proteins are organic compounds. Each of the proteins in turkey is composed of organic building blocks called amino acids, of which 20 are naturally occurring in humans. The best way to think of the “turkey protein” is via analogy using colored popcorn on a string. Long before electric lights, people would decorate their Christmas trees with just about anything, including long strings of popcorn, the organic alternative. Imagine 20 different colors of popcorn randomly placed onto a thread via threading with a needle leading to a strand that is 30 feet long. Now imagine that strand of threaded popcorn being arranged in loops, twists and a variety of shapes. What you now have is essentially the three dimensional structure of a protein.
Glycine is a common amino acid in proteins. It’s the “blue” component of the “turkey protein” (Scheme 1). For simplicity, the carbon and nitrogen atoms originating from glycine are color coded in blue. After enjoying and chewing that bite of organic turkey sandwich, it’s pleasantly on its way to your stomach, where it is partially digested. To simplify matters, let’s imagine the protein being “carved” into amino acid components in the stomach. For our purposes, glycine is the key player. It takes a rather “long ride” in the body, and is eventually turned into a major component of hemoglobin, the oxygen transporting protein of the body. Oxygenated hemoglobin is responsible for the characteristic red color of red blood cells. Indicated in the scheme is the heme b group of hemoglobin.
Red blood cells live, and red blood cells die. When they die, they’re eventually carted off to the liver and other places where the heme group is converted (via catabolism, i.e. “downward metabolism”) to a substance known as stercobilin. It’s typical for organic compounds in the body to be turned into other organic compounds. The stercobilin is further catabolized to L-tryptophan, an essential amino acid that is also present in that organic turkey sandwich.
Tryptophan plays a few roles in human biology, one of which is related to the central nervous system. Tryptophan is converted to serotonin, a substance suspected in the maintenance of healthy mood (i.e. happiness). Serotonin is metabolized to melatonin, a substance associated with the regulation of sleep. Thus far, we’ve worked our way from the organic turkey sandwich to happiness and falling asleep.
There’s yet another path that tryptophan can follow (Scheme 2). The body disposes of tryptophan by converting it (intestinal bacterial degradation) into a substance known as skatole, the primary aromatic component of… poop! Well, on some level, you knew that turkey sandwich was going to turn into poop eventually. We all know the smell of poop very well. Students, while you’re reading this please take the time to thank your parents for changing all those “skatole flavored” diapers for you when you were a baby. Interestingly, skatole has found its way into the perfume industry as a fragrance enhancer. How it was discovered is beyond me, however it’s been determined that small quantities of skatole “improve” the fragrance of perfumes, and might even have an attractant property when it comes to courtship. Believe it or not.
What we’ve seen is that tryptophan takes two entirely different routes impacting the human brain. Via one route, it’s the regulation of mood and sleep. Via the second route is part of the perfume worn by all you ladies out there, ultimately triggering a pleasure center in the brain. As I warned you, life as you know it will no longer be the same. I hereby absolve myself of all responsibility for imparting unto you this interesting tidbit of Organic Chemistry knowledge.
With certainty, Organic Chemistry is not dull. I guess we should all just be happy I chose not to end this article with a new flavor of Bertie Bott’s Every Flavour Beans.
© 2012 Joseph Lennox, Ph.D.
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