This article was first published in The Montreal Gazette.
I have a soft spot for carbohydrates. That’s because they helped launch my scientific career. Many, many moons ago, my PhD research explored the subtleties in the molecular structure of simple carbohydrates using an instrumental technique known as nuclear magnetic resonance spectroscopy (NMR). My experiments had nothing to do with nutrition, but generally the first task of a fledgling scientist before engaging in a research project is to check the literature and see what is already known about the subject. As I dipped my toe into the carbohydrate pond, it quickly became obvious that this was no mere pond; it was an ocean.
The term “carbohydrate” was originally assigned to substances based on their elemental composition. They all seemed to conform to the formula Cm(H2O)n, suggesting that they were “hydrates of carbon,” with “hydrate” referring to any substance that contains water. While the formula does generally hold, carbohydrates actually make up a whole family of compounds with starches, cellulose and simple sugars being prime examples.
Besides being the body’s main source of energy, “carbs” affect our lives in numerous ways. Cotton fibres are made of cellulose, a carbohydrate composed of glucose molecules linked together in long chains. Nitrocellulose, made by reacting cellulose with nitric and sulphuric acids, is the basis of celluloid, the world’s first synthetic plastic. Cellulose acetate is used to make eyeglass frames as well as coatings for playing cards. Another modification of cellulose yields carboxymethyl cellulose, a thickening agent used in ice cream and in most cosmetic creams.
Starch, just like cellulose, is a polymer of glucose, but the glucose units are linked together in a slightly different fashion, giving it different properties. It can be used to thicken a stew or bind pulp fibres together in paper. Deoxyribose is the backbone of DNA, chitin forms the shells of crustaceans, and lactose is the sugar in milk that some 70 per cent of the world’s population cannot tolerate. The simple carbohydrate sucrose makes coffee taste sweet, but overconsumption can have a bitter effect on health. High-fructose corn syrup in processed foods is maligned as contributor to obesity, while beta-glucan, a carbohydrate found in oats, is revered for its ability to reduce blood cholesterol.
Given all this, it should come as no surprise that my digging into the carbohydrate literature resulted in an enduring fascination with these compounds. That came in handy when upon graduation I was lucky enough to enter academia and start teaching, which is what I had always wanted to do. I was assigned a course called “Chemistry in the Modern World” that was designed for non-science students. The syllabus was vague, and basically, I could do whatever I wanted.
I had done some teaching in graduate school and became convinced that the way to get students interested in chemistry was by pointing out the role it plays in daily life. While in my own undergraduate career I did appreciate learning about the intricacies of chemical reactions, my fancy was really tickled when the profs mentioned some tidbit about paints, batteries, sea snails that exude a purple dye, chemicals that insects use to attract each other, or nylon being used to make toothbrush bristles. To me these were little gems, but they were just tossed out as an aside, not meant for exam purposes.
When I got the chance to teach, I decided that my emphasis would be on such gems. I hoped that if the everyday applications of chemistry were appreciated, students would be motivated to learn about the chemical reactions that bring them about. Since at the time I probably knew more about carbohydrates than any other field of chemistry, I thought drawing examples from this domain would be my best chance to kindle interest.
I decided to start the class with what is often considered to be the oldest known chemical reaction, one that even predates the discovery of fire or the production of soap. That is fermentation, the conversion of sugar into alcohol with the aid of yeast. I remember eliciting some chuckles with the line “man’s desire to be drunk is older than his desire to be clean,” one that I would not use today.
Fermentation readily segued into an explanation of why sugar is a carbohydrate, and that in chemistry the term “sugar” is used to describe a number of simple carbohydrates that have a sweet taste. The sweetness in grape juice comes from a mixture of glucose, fructose and sucrose, the latter being composed of a molecule of glucose joined to one of fructose. Yeast, naturally present in grapes, looks on all these sugars as tasty morsels and ends up converting them to alcohol.
I remember then going on to describe how glucose molecules can join together to make either starch or cellulose, and that while we can eat the former, we don’t have the enzymes to digest the latter. But cows do, so they can dine on grass.
I finished the lecture with the story of nitrocellulose, explaining that it is a highly flammable substance and was given the name “gun cotton” because at one time it was rammed into a cannon and ignited to produce the expanding hot gases needed to propel a cannon ball out of the barrel. To cap things off, I lit a sample of gun cotton and was pleased to see the students gawk in amazement as it instantly disappeared in an orange flame without producing any smoke. This, I explained, was the birth of smokeless gunpowder.
I followed with a historical account of how French industrialist Hilaire de Chardonnet discovered that when a solution of gun cotton is extruded through a shower head-like device, the solvent evaporates, leaving behind a thread resembling silk. This was then woven into the world’s first synthetic fabric that looked like silk and felt like silk. But it had one big drawback: It was highly flammable. Workers in the factory that produced it took to calling the novel fabric “mother-in-law silk.” There’s another line I would hesitate to use today, especially given that my first class of 30 students has expanded to a class of 1,000.
The story of carbohydrates has expanded as well. Now we talk about using genetic engineering to help crops produce starch that resists digestion and feeds the microbes in our colon that then crank out chemicals with a host of health benefits.
Looking back, carbohydrates were not only instrumental in forging my career, they have also helped in igniting an interest in chemistry in generations of students. And, yes, I still do the gun cotton demo. Even though today’s students have grown up with all the technological wizardry, they are still amazed.
