If you crack open an egg by dropping it on the floor, the result is a liquidy, and now useless, mess of yolk and white and shell shards that takes forever to clean up. If you had boiled that egg for a while before dropping it, however, the shell would be cracked but the egg itself would be firm and still usable. Just pick it up, peel it and you’re ready to go.
How can this happen, you may ask, and on one level, the answer is simple: the denaturing of proteins. Why should you care? Because the human body consists of a lot of proteins, and the same thing that happens to the egg can happen in your body, for better or for worse.
What are proteins?
There are three so-called macronutrients in your body: fats, carbohydrates and proteins. Proteins are physically long molecules made from a chain of 100 to a couple of thousand simpler building blocks called amino acids. Proteins are the building blocks of your bones, muscles, skin, hair, blood and more. They are used to make enzymes and hormones, as well as other body chemicals, and to repair tissues.
Proteins are the primary workhorses in each of the trillions of cells in your body. They allow your body to break down the food you ingest and to power your muscles. They use your brain to send the signals that control your body, and they use your blood to transport nutrients to wherever they are needed.
Yet, this vast array of proteins has a lot in common, including that they all consist of just a few chemical elements: carbon, hydrogen, nitrogen and oxygen, as well as some others such as potassium and sulfur in “side chains.” And how they can account for so many different functions in your body has again a somewhat simplified answer, folding.
Proteins don’t like to remain as straight chains. In fact, those that are straight are usually either useless or toxic. The genetically guided, precisely folded, 3D shape of each protein completely determines the function of that protein, its nature. Once created, they begin to fold, and the precise shape into which they fold is held together by different bonds in different proteins. These are fairly weak bonds among the folds in eggs.
What happens to the egg?
The quantity of protein in egg white is about 12 percent, and about 16 percent in the yolk. This is a pretty high concentration, and so any change in the protein structure is bound to have profound effects on the structure of the egg.
Although there are variations in technique, the common way of getting hard-boiled eggs is to put them in cold water and then heat them. The procedure is simple, but what’s happening inside the egg is not simple.
Cast your mind back to high school physics, and remember that as heat is added to any substance, its molecules begin to vibrate physically. The higher the heat, the more vibration occurs up to the boiling point. Within the egg white, as the heat climbs to just under 160 degrees, the vibration is so great that the weak bonds holding the folds together are broken physically, and the protein unfolds. That is, the nature of the protein defined by the folding is undone, and we say the protein is denatured. For the protein in the yolk, the denaturing temperature is just under 160 degrees. Once straightened with the heat continuing, the protein strands clump together, force out any water and form much stronger bonds. They solidify.
A culinary note: It’s better not to actually boil the eggs because the more heat is applied, the stronger the bonds in the denatured protein strands become, and the more tough and rubbery the egg whites become.
Interesting also is that denaturing their proteins does not affect the excellent nutritional value of eggs. This is because even though the protein function is disrupted by denaturing, the basic amino acids that make up the protein are not affected, and so their nutritional value is preserved.
Denaturing the proteins in your body has a variety of results, some that are critical to life and some that are life-threatening.
The downside of denaturing your proteins
As one example, you may remember that ages-old wisdom that when you have a fever, it’s critically important to keep it below 106 degrees. This had been observed long before denaturation of proteins was a known concept. As it happens, however, most of the proteins in your body begin to denature at 105.8 degrees. This means that if your body temperature goes over that value more than briefly, you are likely to notice degradation in an assortment of functions, and your condition may even become life-threatening.
The good news, assuming you live through a high fever, is that for your proteins, denaturing is a reversible process. That is, when your fever is lowered below the critical temperature, your proteins regain their native shape and function.
Clearly and thankfully, denatured egg protein is not reversible. Once the egg is hard, it will not become liquid again. If it were reversible in eggs, you would have to eat your hard-boiled egg very quickly!
Daily denaturation
As it happens, the process of denaturing is also critical to sustaining your life. This is particularly evident in digestion of the food you eat.
Your small intestine goes from your stomach to the large intestine and is the area where much of the nutrient value of your food is derived. Alas, however, your small intestine can absorb only single amino acids, and so the gigantic proteins you ingest are useless in their native shape.
The digestive enzymes in your system are designed to break down the bonds between amino acids, but not the larger protein structure that prevents the enzymes from doing their job. And so, a major task of digestion is first to denature the incoming proteins, and this process begins in your stomach. As soon as you smell or taste or ingest food, there are cells in your stomach lining that secrete hydrochloric acid, which does the job of denaturing food proteins as soon as they reach your stomach and does so just as effectively as heat.
Denaturing for fun
The oldest depictions suggest that the hairstyle industry has been around for at least 30,000 years. The vast number of always busy hair salons in this country alone is testament to the joyous practicality of denaturing in making us feel good about ourselves. Human hair is a protein called alpha-keratin, or usually just keratin. The entire industry of hair treatment is based on the properties of keratin when denatured. For 2019, the value of the hair care market is estimated to be about $89 billion.
The natural state of your hair — curly, straight, frizzy — is determined by a particular kind of bond in the keratin protein, a bond that is much stronger than the weak bonds in other proteins. It’s called a disulfide bond. Because of the strength of disulfide bonds, you cannot straighten your hair simply by heating it. Rather, keratin needs to be denatured chemically, which accounts for some of the dreadful smells one encounters at hair salons.
Having denatured the keratin, one can then put in curlers and other tortuous devices to manipulate your hair to the shape you desire. Another smelly oxidizing concoction is then applied to form new disulfide bonds that will preserve the new shape.
Alas, however much you like your new “permanent wave,” it’s not really permanent for two reasons: First, the disulfide bonds in the new structure are not as strong as the natural ones, and so they will break of their own accord over time. And second, the denaturing and restricting applies only to the hair that can be seen, and so as your hair grows out, it does so following the demands of its genetically guided native program. What was straight will be straight again, etc.
This is good in that having to get new “permanents” regularly ensures the permanence of the hairstyle industry for at least another 30,000 years.
Bob Keller maintains a holistic practice in Newburyport. He offers medical massage therapy for pain relief, as well as psychological counseling, dream work and spiritual direction. Many patients call him Dr. Bob and accuse him of doing miracles, but he is not a medical doctor nor a divinity. His expertise is medical massage therapy, understanding this miracle we call the human being. He can be reached at 978-465-5111 or rk2name@gmail.com.