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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 in 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 into 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 tunneling.
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
describes 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 chlorophylls, 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 you 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
away 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, like 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.
