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Quantum Biology: What physics can tell us about life

A field of study called quantum biology says everything we know is wrong…

Well, more accurately, everything we know might be wrong, or might be right, or both, because, you know… quantum stuff. For the uninitiated, just in case you’re wondering what we’re on about, anything to do with the quantum world is just inherently confusing and cannot be easily understood or tested. And because everything in the quantum world is neither this nor that, or rather, both this and that, it’s pretty much impossible to know anything for sure until we can better understand quantum mechanics.

The field of Quantum Biology is basically the joining of hands of quantum physics and biochemistry to mess with our minds even more than theoretical physics can. Of course, some think that quantum biology is really just the typical quantum physicist’s ego acting up and wanting to show superiority in yet another field… but we’ll avoid this in order to prevent World War III.

What is it?

So what’s the idea behind quantum biology? Well, as quantum physicists would remind you, everything is just quantum particles in the end. Whether it’s a single hydrogen atom or the entire visible universe (which is about a billion light-years across), it’s all essentially made up of little quantum particles. Now, we’ve differentiated the science fields by using the logic that made sense back when we didn’t know that quantum mechanics existed, and so we went by what was visible. Stuff to do with bodies and motion, and mass, etc. were all lumped into physics, anything to do with how elements react with one another by using bonds, and swapping electrons, etc, was lumped into chemistry, and of course, the study of everything living was dumped under biology.

Just a tiny, tiny sliver of DNA

Even with classical science, we have an overlapping of sorts. For example, we learned that DNA was just a chemical (a really insane chemical compound, but a mere chemical nonetheless). Then there was always the physics of living things that invaded biology – when you want to know how fast the cheetah runs, it’s calculated using physics, even though the question might seem like a biology one.

Because of the overlapping, we had biochemistry and biophysics; what we didn’t have was phemistry or chemysics, or whatever… Then, once we discovered that we could observe far smaller things, and then even tinier organisms, etc., we had microbiology. Now, going down to the extreme levels of zoom, and witnessing the tiniest of particles in the quantum world, we finally have the field of quantum biology, which is nothing more than physics, chemistry and biology meeting biochemistry and biophysics, and throwing in quantum mechanics and quantum theory for good measure. Only the string theorists are left alone in the corner wondering about infinite universes…

Of course, quantum physicists are used to isolating quantum effects and studying them at near absolute zero temperatures (-273 degrees C), while biology is done at relatively hot temperatures with a billion different things happening at once… so it’s certainly not an easy field to study.

Is it new?

Heck no! As early as 1944, Erwin Schrödinger, the famous Austrian physicist, known more for his cat thought experiment than anything else, published a book called What is Life? In it, he looked at life (or biology in general) through the lens of a physicist. Much before DNA was discovered, in this book, he suggested that perhaps there was some storage mechanism of information inside all living things which told them what they were and how to grow, etc. He thought it might be a special crystal of some type which contained information inside its chemical covalent bonds. Needless to say, when James Watson and Francis Crick discovered DNA’s structure in 1953, using an amazing photograph taken by Rosalind Franklin, they listed Schrödinger’s book as an inspiration.

An altered version of Rosalind Franklins DNA photograph that indicates A-DNA and B-DNA

The lies you’re told

You might think it’s all been discovered, and there’s nothing really left to work on in biology. Nothing could be further from the truth. Take DNA, for example, we all know it’s a chemical compound, we even know the shape, the base pairs, the structure, and although expensive, the Human Genome Project (HGP) spent billions of dollars sequencing a whole human genome. Except, they didn’t.

Most of us think the DNA analysis that crime labs do are merely a case of popping some DNA into a machine, which reads the whole sequence from start to finish, and then compare that to a suspect’s DNA and then we go “Aha! Caught you!”, if it’s a match.

Nothing is further from the truth. We all know DNA is made up of the “letters” A C G T. Here, A = Adenine, which is actually C5H5N5, Cytosine is C4H5N3O, Guanine is C5H5N5O, and Thymine is C5H6N2O2. Now, when we heard that the HGP had sequenced the human genome, we tend to think of it as the entire genome of a human was read from start to finish, it wasn’t. Human DNA is 3 billion base pairs long – in sperm and eggs with 23 chromosomes; and 6 billion pairs long in non-sex cells or 46 chromosomes. This makes it impossible for any technology we have currently to just read the entire DNA strand. Instead, the DNA is broken into chunks, and then the bits and pieces read and then arranged together to form the readout. Think of it like a jigsaw puzzle, except this one has a hundred million pieces! When the HGP was completed in 2003, it still had gaps in the DNA that weren’t sequenced. This is because although all the chunks of DNA were read (think of it as having all the pieces of the jigsaw), there were a few patches where everything seemed to fit, and thus, we couldn’t tell what was the actual piece that went there. Think of this as a clear blue sky in a jigsaw where many pieces are almost identically shaped, and you really don’t know which one goes where in order to be able to complete that featureless patch of blue sky. (An oversimplification, obviously).

In essence, there’s a lot about DNA that we still don’t know but can guess, and even more that we have no clue about.

The reason we took the DNA detour is to establish that we really don’t know a lot about things laymen like us think scientists know everything about… and it’s not just limited to DNA.

Birds

For decades we’ve known that birds migrate to and from very specific places on earth, down to a meter accuracy on journeys that can last thousands of kilometres, and in varying weather conditions, and even when flying at night. So how do they do it? We’ve set up radar stations, GPS satellites and use advanced techniques to navigate in our high tech aircraft, while birds have been doing it successfully for far longer than we’ve even been human.

In school, we’re all told that birds can sense the magnetic field of the earth, and that’s how they migrate. Something inside them allows them to feel the extremely weak lines of magnetism, and follow them due north or south, depending on the season. This part was never explained to us though – not if you had a good science teacher who didn’t speculate because we just don’t know how they do it. No theory was able to properly explain how birds are able to sense magnetic fields.

So how do they do it?

That’s where quantum biology comes in. A whole lot of researchers have done experiments and found that birds need light to hit their eyes to be able to sense the magnetic field. Not even sunlight, but even the dim lighting of night time works. There were a ton of experiments run to settle on this, including putting hoods on birds to cover their eyes, and playing with magnetic fields, and it became obvious that light had something to do with a bird being able to sense magnetic fields. Now, even more research has shown that there are cells in all birds’ eyes which contain a light-sensitive protein called cryptochrome, and these proteins are activated by blue or green light and create what is known as a radical pair. This is a pair of electrons in a molecule with opposite spin – quantum-entangled electrons.

Examples of the vast distances some birds migrate

So when a photon is absorbed by one of the electrons, it jumps to a higher state (or a higher orbit), and this makes the electron pair more susceptible to the magnetic field of the earth. The longer the electron stays in the higher orbit, the more accurate the reading. This reading is done when the electron finally jumps back to its original state and lets off a small quantum of energy, which is dependent on how perturbed the electron was by the magnetic field. Birds may be sensing the magnetic lines of the earth and actually seeing them the way we draw them on maps ourselves!

Just an example of the magnetic field lines in 2015

Honestly, this could still be proven wrong, but all experiments done so far have upheld the theory. So, birds? That’s what quantum biology is about? Actually no. There’s even more evidence emerging that is pointing to quantum effects being responsible for all life as we know it!

Photosynthesis

Although most life isn’t photosynthetic, and some doesn’t even depend on the process at all, not even for food, it’s pretty obvious that life on earth thrives because of its ability to use sunlight to make food. Plants and bacteria make food from sunlight, then they are food for herbivores and other bacteria, which in turn are food for carnivores, and everything eventually dies and becomes plant food or bacteria food, and the circle of life is complete. Take away photosynthesis, and earth would be a very barren place indeed, with (maybe) a few extremophiles living near undersea volcanoes, and that’s about it.

For decades we’ve felt that we understand all there is to know about photosynthesis. All of us have learnt that sunlight falls on leaves that contain chlorophyll and then something happens and the plant is able to make food by using sunlight and carbon dioxide to “eat” carbon and give out oxygen… and it’s why we’re all here… so plant more trees… Sound familiar?

Oversimplified reaction of photosynthesis

If you’re a little more into biology you will know the explanation that involves chloroplasts and photons and reaction centres. The shortest version we can muster for the purpose of this article is that photosynthesis happens in light-dependent and light-independent reactions, and it’s the light-independent one that actually breaks apart carbon dioxide. The light-dependent reaction breaks water into hydrogen and releases oxygen. Thus, the whole “plants use sunlight to extract oxygen from carbon dioxide” idea can be considered wrong depending on how much of a stickler you are for accuracy.

For the light-dependent reaction, photons hit chlorophyll molecules, which excites an electron in the molecule. These excited electrons are transported away, and the chlorophyll molecule replaces its missing electron with one from a water molecule, which ends up breaking up the molecule into hydrogen ions (protons) and oxygen. The hydrogen ions then attach to some complex compounds with the help of enzymes, and all of these undergo a light-independent chemical reaction that we know as the Calvin cycle – named after American chemist Melvin C Calvin who mapped the cycle using radioactive carbon. Although far more complex a reaction than we can explain here, what this cycle essentially does is absorb and use carbon dioxide from the atmosphere.

The Calvin cycle is pretty complicated…

The reason for that crash course in photosynthesis is to explain that the excited electron (called an exciton) jumps from one chlorophyll molecule to another, making a pathway to what’s called the reaction centre, where all the chemical reactions occur. Think of it as how you eat with your mouth, but digest with your stomach, because it would be inefficient to have stomachs where our mouths are.

However, transport of electrons uses up energy, and there’s no one path that this electron can take because of how many paths there are. Plants are always growing new leaves and new cells and the system is very dynamic, so it seems obvious that there should be energy loss when transporting excitons, and yet there isn’t. Turns out, the electron transport process in the reaction is almost perfect, which is more indicative of something quantum happening there, rather than a classical physics explanation.

This is where the probability wave that electrons use comes into play, and another effect we call quantum coherence. Basically, while classical physics thinks of it as the exciton traversing a path down from the chlorophyll molecules to the reaction centre, quantum coherence suggests that the electron is a wave, and so is essentially finding the most efficient path, without losing energy. The excited electron is actually taking all the paths, and none of them, at the same time! (Don’t blame us, everything quantum is weird.)

Do you smell that?

We’ve already overshot the word count for this article, but we cannot leave before mentioning something that isn’t about birds and plants. There’s quantum biology at work inside us as well, and one place it’s being studied is inside your nose.

We’re not going to go into depth here, so you might need to do some of your own research as well. The sense of smell that we have (or rather that all animals capable of it have) works by having various receptors in the smelling apparatus (the nose in our case) which is like an incomplete jigsaw puzzle. Actually, it’s like many different two-piece jigsaw puzzles.

Imagine a few hundred molecules of something near you (dog poo, for instance) wafts into your nose. Your nose actually has receptors that have holes in the shapes of various commonly found chemical compounds and when a molecule fits into place, a signal is sent to your brain saying “found molecule xyz”. Your brain has trained itself to recognise xyz as something (dog poo in our example), and then you go “eww”! Depending on the saturation of molecules entering your nose (which is a function of how close you are to something), the smell can be anything from faint to intense to even overpowering. This is the classical biology understanding of the sense of smell.

So why do some things with the exact same shape, still smell different then? This was what was found by researchers who replaced hydrogen in compounds with deuterium (a heavier hydrogen atom with a proton and a neutron). Chemically it’s the same compound, has the same shape, and should fit perfectly into the same smell receptor in our noses, and yet it smells different. This has been confirmed by double-blind tests, so it’s apparent the shape theory of smell is sorely lacking. Quantum biology comes up with a hypothesis, and it has to do with the vibrations of the molecule. Because the mass of the deuterium molecule is higher, it vibrates differently. Could noses be sensing not just molecules but also how they vibrate? A theory suggests that receptors in noses might be utilising quantum tunnelling of electrons to detect vibrations of molecules that attach to them.

Biophysicist Luca Turin came up with the “vibrations” theory of smell

Imagine quantum tunnelling to be akin to wanting to throw a ball (an electron) into a house (another molecule) that has locked glass windows (barrier). Instead of breaking through the barrier and smashing the window, imagine if the ball just disappeared from this side of the window and appeared inside the house. Because quantum mechanics suggests that electrons can be in two places at once, this is totally commonplace in the quantum world, and experiments have very much proven this. Tunnelling happens all the time when it comes to electrons or photons, and other quantum particles, so there’s no reason to assume it is not happening inside our noses. What hasn’t been proven is that it is the cause for us smelling heavy hydrogen elements differently.

Problems

As you can see, the biggest problem with us being able to put these quantum biology theories to test is the problem of noise and complexity. We are just not skilled enough, and might never be capable of testing some of these theories, but we certainly should keep trying. We all know that the same quantum effects are responsible for a universe existing, when none should have, and there are quantum biologists who insist that the very reason for evolution and natural selection of life… mutations… might very well happen because of quantum effects.

For now, we put quantum biology under our ignorance section, but if all it proclaims to happen actually does happen, we might have to put everything we think we know about biology in this section! Either way, there is so much to learn still. In science, ignorance is bliss, because it means big grant money!

Robert Sovereign-Smith