This topic was chosen by one of our patrons. Hello mortals. Ever heard of quantum physics? I’m sure you did. Biology? Of course. Now what about - quantum biology? This is not a simple combination of words
to make you sound intelligent, but an entire field of study which analyzes the applications
of quantum mechanics to biological objects in order to explain things like random mutations
in DNA, how do birds orient themselves while migrating, how does photosynthesis work and
even what’s going on i
n US politics. One of them is a lie. After watching some top anime crossovers,
the first person to think of combining quantum mechanics and biology was none other than
our cat-loving Erwin Schrödinger. He even wrote an entire book on this topic. There, he introduced the idea of an aperiodic
crystal which contains genetic information in its chemical bonds. Afterwards, he suggested that mutations in
this crystal somehow happen because of quantum leaps – electrons “jumping” from one
energy level to
another. After a few years, a molecular structure in
cells which preserves information was discovered, now known as DNA, which acts as the instruction
for making proteins. It consists of these 5 nucleotides. Inside the DNA, those nucleotides are tied
in pairs by several hydrogen atoms and form this well-known spiral. We will focus on only two of those pairs:
During the DNA replication, there is a small chance that the Hydrogen atoms will change
their places thereby transforming the G:C pair int
o the T:A pair or vice-versa. This will cause an alteration in the genetic
code and therefore – a mutation. However this transfer of a hydrogen atom from
one place to another requires a lot of energy and cannot be explained by well-known mutation
models such as ultraviolet radiation, oxidative damage or… this thing. Then the Swedish physicist - Per-Olov Lowdin
came and presented his quantum model of mutations in bio-chemistry. He suggested that this transition is made
possible due to quantum tun
neling. This weird thing is a phenomenon where a subatomic
particle passes through a potential barrier that it cannot surmount under the provision
of classical mechanics. In other words, it permits the teleportation
of a particle to a place where it shouldn’t be able to get because of the lack of energy. For example, by quantum tunneling, the hydrogen
particles are able to form helium nuclei – that’s how the fusion process works inside the Sun. If we look at the Schrodinger equation which
descri
bes this process, we’ll see that the probability of tunneling depends on the mass
of the particle. In other words, the heavier the particle is,
the less of a chance it has to tunnel. And this fact was used to demonstrate the
Lowdin theory. What if we replace the normal hydrogen atom
from the DNA with its heavier isotope Deuterium? In this case, quantum tunneling should occur
less often and thereby the rate of spontaneous mutations will decrease. And recent experiments prove that. Scientists grew
a culture of bacteria in a
Deuterium oxide (D2O) environment, and their cells showed fewer mutations than bacteria
grown in normal water, proving Lowdin’s theory. So you can thank quantum physics if you have
a lactose tolerance or no wisdom teeth. Now moving on to photosynthesis – the process
of converting solar to chemical energy in plants. They absorb the energy coming from the sun
in form of photons using the chloroplasts inside their cells, which contain some special
molecules called chloro
phylls, the ones that give leaves their green color. So, when a photon gets inside a chloroplast’s
antenna and hits a chlorophyll, one of its electrons gets excited and uses the extra
energy to bounce through the antenna from a molecule to another to a reaction center. There, the gathered electrons create a permanently
separated charge that is, in essence, stored energy ready for use by the plant. There is a problem however. Getting to the reaction center is a very hard
procedure to accomplish,
because in one chloroplast’s antenna there are hundreds of thousands of
chlorophylls. And this intermediary action of passing from
one molecule to another has to be done quickly. If the electron doesn’t get there in a nanosecond,
bouncing randomly through the molecules will absorb all of the photon’s energy, making
the whole process useless. So the electron has to find the shortest path
from the first molecule to the reaction center. But how? The plant doesn’t know of any path-finding
algorithm
to get the shortest trajectory for every electron. Here’s where quantum physics comes into
play, and more precisely - quantum superposition. This principle states that a particle can
be in various places at the same time, thus occupying multiple positions at once. And it turns out that plants and algae employ
quantum superposition so that the electron can simultaneously travel among all possible
paths. That way, it always get to the reaction center
every time through the shortest path. But do yo
u know what can be cooler than eating
light? Being able to smell magnets. That’s exactly what magnetoreception is. The ability of feeling the magnetic field’s
lines’ direction and intensity, knowing where the poles and the equator is, is used
by a range of animals for navigation and migration. As an example, we’ll take the migratory
birds named European Robins. Those feather balls migrate each year from
Northern to Southern Europe and vice-versa using the Earth’s magnetic field. But how exactly
do they detect it? Well, scientists don’t know the exact answer,
though there are some hypotheses. The most boring one is that they have a substance
named magnetite somewhere in their body which is sensitive to the magnetic field. However the most fascinating theory is as
always the one that has quantum physics in it. It says that migratory animals use a special
protein in their eyes named Cryptochrome. When a photon enters the eye and hits one
of those molecules, one of its electrons bounces aw
ay and gets to another Cryptochrome, forming
that way two radicals- one negatively charged and one positively. And here’s where we introduce quantum entanglement. I spoke about this principle in this video
and you can go and watch it to understand what it is, but briefly quantum entanglement
is the ability of two electrons from the same energy level to keep opposite spins. And even after one of the two entangled electrons
leaves the energy field, both electrons will keep opposite spins relative
to each other. Same with the electrons of the Cryptochromes. Depending on the electron’s spin, it reacts
differently to the magnetic lines, and in that way, it allows the pair of radicals to
align themselves to the magnetic lines and react differently at different angles. In that way, those animals can understand
where they are located in reference to a magnetic pole and the equator. And these hypotheses aren’t the only ones
that use quantum physics at explaining biological phenomena. Others, li
ke the sense of olfaction, vision,
the effectiveness of enzymes and even the presence of consciousness could also be explained
using principles from quantum mechanics. And maybe this way, you insignificant mortals,
will feel as being part of the quantum world – part of something bigger, something important,
at least for a little bit, not that it would change anything.
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