Energy, Information, and Life
Or Biophysics: A Love Story
The title of this post is taken from the subtitle of Biological Physics, a textbook written by Professor Philip Nelson. I had the pleasure of taking Professor Nelson’s course in biophysics during my second year of college, and I can honestly say that it was a class that changed my life.
This story goes back to Fall 2011. I was applying for colleges, and had to choose a potential major to put down on applications. At that point, I was unsure of my post-high school life. My vision of the future was a completely blank slate. I had an interest in pretty much every subject in school. I briefly considered going to school for music, for economics, for writing. I had a notion of the “liberal arts” that appealed to me, making choosing a particular subject difficult. Ultimately, I fell back on my long-held dream of being a scientist, and wrote “physics” down for the applications.
I ended up choosing to go to Penn, partially due to being offered a spot in the Vagelos Molecular Life Sciences program. Granted, the program has a biochemistry focus, but it seemed like a good opportunity (and came with two summers of paid research). Besides, I had enjoyed AP Physics, and at that point had convinced myself that studying physics would provide me with a solid general science education. Thus, I entered college with the intention to major in physics as well as biochemistry.
That changed when I took Professor Nelson’s course. I had never heard the word “biophysics” before (much like many people I tell that it is my main academic interest). My eyes were opened to a field of study that left me wide-eyed at all of its possible applications.
So what is biophysics? My short answer would be that it is the study of biology using quantitative techniques from physics. Just as physics attempts to explain physical phenomena with mathematical models, biophysics explains biological phenomena in a similar way.
My longer answer would be pointing out some of the landmark biophysics publications of the 20th century. Foremost among these is “What is Life?” by Erwin Schrodinger (the physicist best known for that goddamn cat in the goddamn box), written in 1944. This paper, based on a lecture series Schrodinger gave, centers around the question, “How can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?” His analysis ranges from a prediction of how genes are encoded to discussing how life seemingly defies entropy (the universe’s tendency towards disorder). The epilogue, which is titled “On Determinism and Free Will,” is perhaps most interesting, though it sounds like Schrodinger was high out of his mind when he wrote it. Bizarre philosophical musings aside, “What is Life?” contains many insights about biology and is widely seen as the founding work of biophysics.
The year 1952 was another important year. This was the year that Alan Turing, the well-known mathematician, computer scientist, and codebreaker, published a paper on morphogenesis. This paper used mathematical modeling and theory to predict why certain patterns appear in nature. Such patterns, which include distinctive spots and stripes on many animals, are now known as “Turing patterns.” Essentially, Turing took the age-old question of “How did the leopard get its spots?” and derived an elegant answer from math and biology. Also in 1952, two British researchers named Alan Lloyd Hodgkin and Andrew Huxley developed an ingenious model of an individual neuron by imagining neurons as electric circuits. The two won a Nobel prize in 1963 for their groundbreaking work, which was a crucial discovery in the field of computational neuroscience.
The list goes on. Some of the most mystical biological questions have been at least partially explained by physicists. Personally, I am fascinated by the way that the field accomplishes this by using ideas that often seem simple or abstract. This is why the subtitle of Nelson’s book resonates so strongly with me. Energy, information, and life are all very abstract quantities, and yet all can be studied with scientific rigor.
If you look in an introductory physics book, energy is the ability of a system to do work. If you ask a New-Age hippie, energy is a mysterious entity with almost sacred properties. Biophysics defines it as somewhere in between. Yes, it really is the thing that allows for forces to do work on objects, but energy in biology takes on a crucial importance that may as well elevate it to divine status. It is the thermal energy of molecules that allows diffusion to drive so many biological processes. It is the bond energy of various molecules that allows metabolism to work. Life would not exist if organisms were at perfect equilibrium with their surroundings — we call that state death. The fact is that our bodies are miraculous machines that are able to extract energy from the environment in order to do things like run and throw and even think.
The sheer number of predictions that can be made by analyzing energy is staggering. Energy is truly the universal currency of biology, and there is something beautiful about how this one concept is so widely applicable. From just a few guiding principles of thermodynamics, it is possible to learn so much about how life manages to exist.
Information is a rather complicated topic, but is also very important to biology. Our chromosomes exist for the storage of genetic information, and one could say that the purpose of life is to successfully pass that information on from generation to generation. Information is closely tied to entropy, or disorder of a system. To put it simply, if a source of information is more unpredictable in what it says, the more information it contains. If you have a predictable pattern, it contains less information than a non-repeating, random series. What is amazing to me about information theory is that it allows you to quantify the abstract concept of information — for example, the amount of information conveyed between two neurons. And the fact that this quantifiable information is a key measurement of biological systems is absolutely mind-blowing to me.
What I love most about biophysics is the sense of wonder it instills in me. Just because it is possible to elucidate the most mysterious secrets of biology does not make our own bodies any less incredible. To the contrary, the fact that our cellular machinery is driven by laws of statistics and diffusion, and that out of all these processes we emerge as whole creatures, makes our existence practically inconceivable. Yet here I am, the product of billions of years of evolution, typing away at a machine that, though it can compute the square root of two in a split second, has but a fraction of the computational complexity of my brain. And, as Schrodinger wrote in his epilogue, it does not mean that we are strictly deterministic machines. No, the statistical uncertainty of our biological processes leaves plenty up to random chance, and, dare I say, free will. The very mechanism of free will, or consciousness for that matter, has yet to be discovered, but I know that when we find it, it will make us seem no less amazing. For to understand life is to understand ourselves, and to understand ourselves is to understand the way that the universe observes itself.