There are few truths clearer and more apparent as: life is made possible by the energy of the sun. What we call the second law of thermodynamics teaches us that built into the fabric of the universe in an arrow of time and entropic progression. To find balance, the universe creates order, dissipative structures, that can absorb and more efficiently facilitate that flow of energy. In our case, order and life is formed on earth to properly facilitate the light energy flowing from the sun. From this point of view, one can view the entirety of biology as something invertedly tied to the light and electromagnetic waves. From this starting point, we will analyze human anatomy.
Introduction
To begin, a brief review of the electromagnetic spectrum is necessary. What people usually refer to as âlightâ consists of the wavelengths that our eyes can perceive. Photons exhibit both waveâlike and particleâlike properties. They travel from the Sun, reflect off objects in our environment, enter our retinas, and illuminate the world for us to see. In addition to the visible portion, there exists an entire spectrum of photon wavelengths that lie beyond the range of human vision; they are still photons (still light) even though we cannot detect them visually. Below is an illustration of the electromagnetic spectrum and its corresponding wavelength ranges.
The visual spectrum ranges from approximately 380nm to 750nm. Higher energy, shorter wavelengths, beyond our visible blue and purple become ultraviolent (UV) light. On the other end, beyond our visible read is infrared (IR) light. While invisible to the human eye, the other wavelengths of light have played an incredibly important role in the evolution of biological creatures and therefore greatly impact our health.
Light and Electrons
While contemplating how light influences human health, it is first critical to reflect upon how the biology of the earth, in general, handles the light from the sun. To begin, it is best to start off with an example that is apparent and obvious to everyone: plants. Plants, through photosynthesis absorbs the light energy of the sun and transform it. Animals benefit from this transformation by eating the plants and using that energy for their life. Plants use the chloroplasts in their cells to transform light energy into food energy, while animals use the mitochondria in cells to transform the food energy into our energy. A simplified equation for photosynthesis is as follows:
Light + Water + CO2 --> Electrons + Oxygen
A simplified equation for human metabolism within mitochondria is as follows:
Electrons + Oxygen -> Energy + Water + CO2
As is made apparent, plants and animals are mirrors of one another. What the plant absorbs and produces, is what the animal produces and absorbs. We feed each other symbiotically, as we each thrive and absorb what is provided by the sun. What is important to recognize as well is how the electrons transmit from the plant to the animal. What photosynthesis produces is sugar, this is why we retrieve sugars from the fruits of plants. Humans later process the sugars in a way where we can later strip electrons from it for later use in the electron transport chain (ETC) of our mitochondria. Carnivorous animals can also do the same from eating and processing the fat from other animals. Regardless of the source from sugar to fat, these electrons are a consequence of a stream of events whereby a plant utilized sunlight to store electrons in food. In this way, one can imagine electrons as a kind of packaging, that stores the energy from the sun and moves it around to cell to cell, creature to creature. The way at which electrons move in the body is crucial to understand if one wants to truly understand human health.
A plant is able to absorb and process light energy thanks to the pigment compound chlorophyll (Martins et al. 2023). Below is the molecular structure of chlorophyll (Rothemund 1956):
Chlorophyll contains porphyrin rings surrounding a magnesium ion, and has an attached hydrocarbon tail (Martins et al. 2023). Chlorophyll's rings absorb light, exciting electrons within its system to higher energy orbitalsâa leap that destabilizes the molecule. When this happens, the molecule wishes to stabilize and will release the energy. Sometimes an atom may emit this energy as a photon, and sometimes it is done through via resonance of a âvirtual photonâ when another molecule is nearby. The central magnesium atom (Mg²âş) plays a critical structural role: its positive charge organizes the chlorin ring's geometry, enhancing light absorption and facilitating rapid energy transfer. This excitation energy is funneled via resonance energy transfer through neighboring chlorophyll molecules to a specialized reaction center complex in the chloroplast (e.g., P680).
In other words, the energy state of the chlorophyl is heightened, and this energy moves from chlorophyll to chlorophyll to a central place in the chloroplast. Here, the concentrated energy ejects a high-energy electron from chlorophyll, oxidizing it to Chlâş. This electron is then captured by primary acceptors (pheophytin/quinones), entering the electron transport chain. Eventually, the sugar molecule is made. To know what wavelengths of light cause these cascading events, all we need to do is look at the absorption spectrum of chlorophyll. The absorption spectrum of chlorophyll a is below:
Source: https://omlc.org/spectra/PhotochemCAD/html/122.html
As is evident, chlorophyll a absorbs predominantly blue light, while also absorbing UV and red light.
In simplicity, the structure of chlorophyll allows it to absorb light (UV, blue, and red) and dissipate that energy. This, in concordance of many other chlorophyll molecules within the chloroplast leads to the release of electrons for later use by life. One would be simplistic in assuming that this is the total use of light by biological life. In other words, it would be false to assume that only plants absorb light and produce energy, and animals simply benefit from the energy they produce. While this is indeed part of the process, human beings benefit from the light as well. Not only do we benefit from what plants do, but we have also developed even more complex means of processing and benefiting from the light of the sun.
Proteins are Light Harnessing
To begin exploring how animal biology utilizes light, it is perhaps best to review hemoglobin. Hemoglobin is a molecule in our blood that transfers the oxygen that we breathe from our lungs to the rest of the body. The chemical structure of hemoglobin is below (Weissbluth 1974):
The chemical structure is very similar to that of chloroplast. It similarly has rings that surround a metal atom and has a hydrocarbon tail. Meaning, it also absorbs light. A key differentiator is that the metal in the middle is iron and not magnesium (Medlock et al. 2022).
It is then curious to consider to what extent proteins found within the human body absorb light. Furthermore, what do they do with that light energy? Below is the absorption spectrum of hemoglobin (Hb) and hemoglobin with some oxygen (HbO2):
Source: https://omlc.org/spectra/hemoglobin/
Proteins are composed of amino acids, and it is well known that some amino acids that have aromatic rings, such as tryptophan, tyrosine, and phenylalanine, absorb UV light. (Mach, Middaugh, and Denslow 2001; Salmahaminati and Roca-SanjuĂĄn 2024). Furthermore, there is evidence to suggest that the aromatic rings of proteins allows for the efficient movement of electrons, providing a conductive like quality to proteins so that electrons can efficiently move around (Krishnan et al. 2023; Vargas et al. 2013).
To better understand this, let us review how metals conduct electricity. Metals conduct electricity because the atomic structure of metals is such where many electrons exist on the outer most surface, atomically. This collection of electrons provides ideal conditions for the movement of electric energy. One way to imagine it is a sea of electrons, this sea of electrons allows other electrons to easily swim through it. Recall that a similar process occurs in chlorophyll, where light hitting the rings causes electrons to rise, creating the conditions for the movement of energy across chlorophyll. If the aromatic rings of proteins similarly lead to the efficient movement of electrons, then one can imagine the body as full semiconductors. We are made of molecules that, when hit by light, allows for the healthy movement of electrons for healthy bodily function.
To further complexify this inquiry, let us consider how there are only certain types of light that make it through our atmosphere from the sun. Below is a chart of the electromagnetic frequencies of light both admitted by the sun and the rays that pass through our atmosphere we experience on the ground (Horvath 1993):
Note that while the sun emits light of many frequencies, including those close to 0 nm, only wavelengths of around 300nm reach the environment where we live. Now, consider the light absorption spectrum of a protein such as leptin, which responds to wavelengths of 190-210nm (Raver et al. 2000). These wavelengths are in the UV range but are smaller wavelengths than what the atmosphere allows the sun to provide for us. Why did nature form proteins that respond to light not granted by the sun? Where do these wavelengths of light come from? Evidence suggests that these frequencies of light come from within our own bodies. We produce our own light.
Fritz-Albert Popp, a German physicist, is famous for his research involving biophotons. His research has found that living systems emit light from between 200-800nm (Popp, Gu, and Li 1994; Popp 2003). This range of frequencies produced by organic life range from visible light, which seems obvious when one considers phytoplankton and fireflies, but also non-visible UV light. We also emit IR light of course, otherwise we wouldnât be visible via IR goggles.
It is then curious to consider the extent that physiologic functions are dictated by the subsequent biophotons that are produced by other physiologic processes. Later research has found that the bulk of the ultra-weak photon emission produced by living cells is done by the mitochondria (Van Wijk et al. 2020). A meta-analysis paper of the research shows how there are many frequencies of light emitted by the reactive oxygen species (ROS) that are the product of the electron transport chain (Van Wijk et al. 2020). For example, excited oxygen in the triplet state (3O2*) is able to emit a red photon, excited singlet oxygen is able to emit in the 780nm (IR light), and the dimerization of excited singlet oxygen can also emit ranges within our visible spectrum of 634-703nm (Van Wijk et al. 2020).
Light plays an important role in mitochondria function, enhancing its ability to produce ATP more effectively through various mechanisms (Poyton and Ball 2011; De Freitas and Hamblin 2016; Sommer, Haddad, and Fecht 2015). Not only do mitochondria benefit from light, but they also emit light. This light is made possible by the very processes imbedded within cellular respiration. Glucose and lipids are converted into acetyl-CoA, then acetyl-CoA enters the TCA Cycle (Krebs Cycle) which results in the production of some ATP, CO2, and NAD+/ FAD+ being reduced (adding an electron) to NADH and FADH2. NADH and FADH2 act as the next stage of electron carriers, which bring the electron to the site of the electron transport chain (ETC) where the final collection of ATP and water is created. A biproduct of the ETC is ROS, which can emit light. Therefore, there is a feedback process where light makes more efficient the production of ATP, while light is being simultaneously produced by the byproducts of the entire process. In this way, one can view mitochondria as more complex evolutionarily than chlorophyll and hemoglobin, which both utilized light in a more rudimentary way.
One can hardly explore the importance UV light has on the body without mentioning the pigment of our skin: melanin. While plants have chlorophyll, we have melanin. There are different kinds of melanin found within the human body. Below is an illustration of the relevant building blocks for the biosynthesis of eumelanin, pheomelanin, and neuromelanin (Menter 2016):
Notice how the building blocks of melanin all contain rings which make the pigment conducive to absorbing light. Below is an absorption spectrum of melanin:
Image source: https://www.cl.cam.ac.uk/~jgd1000/melanin.html
Notice how most of the light melanin absorbs in in the range of UV provided by the sun. At its surface, this may seem obvious, as we all know that melanin helps protect our skin from UV sunlight. However, just like chlorophyll, melanin also seems to play a role in transforming this light into more productive uses. Research has found that highly melanized fungi show a 4-fold increase in its ability to reduce NADH (Dadachova et al. 2007). This suggests that, when melanin is exposed to light energy, the atoms are moved to a higher energy state, and this can lead to electrons being provided to neighboring molecules. This is incredibly similar to plant photosynthesis. Plants have chlorophyll, and we use melanin for a slightly similar purpose: to absorb light for the purpose of energy production.
Closing Remarks
While this article only scratches the surface of quantum biological topics, it aims to illustrate a lens at which one can view biological life. Biological life formed, and was shaped, around the light energy from the sun. Complex life emerged as organic molecules structured themselves to more efficiently absorb that light and utilize it. Plants and animals alike absorb light, and this leads to the movement of electrons and emission of photons in various ways. Fundamentally, electrons are what drive our bodyâs ability to utilize energy. Mitochondria use electrons to produce ATP, proteins help electrons move around, etc. In many ways, the body is electric, and the sun is our source of power.
We are beings of light. We absorb light and move electrons and photons around our body. We produce light, leading to further life and functioning. We are, and forever will be, in constant relation and harmony with the light of our universe.
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