- Sugar molecules are the currency we use
when we do business with plants.
Certain plants, at great expense,
produce packages of energy for us to eat.
The energy is stored in molecules of sugar.
In return, we swallow their seeds
and poop them out somewhere else, it's a win-win situation.
But how do we know that the plant
is keeping up their end of the bargain?
Well, on our tongues, we have sugar sensing cells.
It's our sweetness receptors
that I talked about in my previous video.
But what if a plant could produce
a counterfeit sugar molecule, a forgery so good
that our tongues couldn't detect them as forgeries?
Well, that's exactly what Pentadiplandra brazzeana has done.
This west African berry produces a protein called brazzein
that stimulates our sweetness receptors,
but it's a much cheaper molecule
to make than sugar molecules.
And primates in the area love it.
They seek out these berries, they swallow the seeds
and poop them out, but they get no calories in return.
The reason this trick is possible
is because our sugar molecule detecting mechanism
in our mouths isn't perfect, it's the old
lock-and-key analogy that I talked about in the previous video.
It's not a perfect system and, actually,
other molecules can be engineered
that also stimulate those receptor proteins.
That's why artificial sweeteners are possible.
Humans have come up with molecules,
like aspartame, that can stimulate our sweetness receptors.
And yet, they contain no calories.
All this talk of artificial sweetener got me thinking,
are there artificial versions of the stimulants of these
other four taste senses that we have on our tongues?
Well, when you taste something sour, as you know
from my previous video, you actually just tasting protons.
Protons are entering your gustatory cells
when there is something acidic in your mouth.
And how do you fake a proton?
So, I don't think there's such a thing as artificial sour.
Salt is different, when you're tasting salt,
it's sodium ions that are entering your cells.
But actually they'll let in potassium ions too.
So, if you put potassium chloride in your mouth,
instead of sodium chloride, table salt,
it should still taste salty.
And, actually, many of us don't have enough potassium
in our diets so that would be a sensible health swap.
In fact, if you buy low sodium salt from a shop,
you'll see from the ingredients that the sodium chloride
has been replaced with potassium chloride.
So, potassium chloride is a kind of artificial salt.
Actually, it doesn't taste exactly like salt.
And I don't know why, I'm not sure anyone knows why actually
What about artificial savoriness or artificial umami?
Well, your umami taste is your protein detecting mechanism,
but it turns out you can actually use
the mechanism against itself.
With umami, you're not detecting protein molecules directly.
You're detecting glutamate molecules that tend
to be present in foods that have proteins in them.
So, that means you can use the glutamate molecule
to trick yourself into thinking you're getting protein.
Like if I order a vegetable chow mein
from my local Chinese takeout,
the likely put a lot of monosodium glutamate in it
and it will taste very savory to me
as if I'm getting lots of protein
in my meal when I'm definitely not.
What about artificial bitter?
Well, I'll get to that in a minute
'cause it's a whole thing.
First, I just want to address a question
that I got a lot in the comments of the last video,
which is what about hot chilies?
Well, the capsaicin molecules in chili
that make them hot are a kind of trick,
like artificial sweeteners, but they're not messing
with one of our taste receptors.
They're messing with our thermal receptors.
We have different proteins on the surfaces
of our cells that change shape at different temperatures.
There's one that's activated
at around 42 degrees centigrade.
And we register that as painfully hot.
And capsaicin binds to that protein,
which is why when you eat chili, it's a weird kind of heat.
None of the thermal receptors below painfully hot
are being stimulated in the near vicinity.
It's a confusing kind of hot.
Why did chili plants make capsaicin in the first place?
Chili seeds are dispersed in the guts of birds.
The birds eat the chilies, they swallow the seeds
and they poop them out somewhere else.
Those same chili seeds in a mammalian gut
are destroyed by enzymes and acid.
In other words, chilies don't "want"
to be eaten by mammals because mammals destroy the seeds.
So, chili plants evolved capsaicin molecules
to dissuade mammals from eating their fruit.
The proteins that birds use to detect temperature
are different to the ones mammals use
and capsaicin doesn't bind to them.
So birds don't feel the heat from chilies.
Looks like a fun book that.
"Wild Scientists," called Clever Creatures in America.
Oh, by Steve Mould, that's me, it's a good book.
If capsaicin is meant to be a deterrent,
then why does so many humans enjoy it?
Well, no one knows for sure.
One simple answer is that, well, humans are weird.
Like why do we enjoy scary movies and rollercoaster rides?
They give us a sense of danger,
but we know they're not actually dangerous.
It's a form of benign masochism.
Bitter taste is your poison detecting mechanisms.
So, any molecule that tastes bitter,
but isn't poisonous is, by this definition,
an artificial bitterer and scientists have
certainly found a number of those.
Denatonium, for example, found in products like Bitrex.
In this form, you put it on your nails
like nail varnish and it stops you
from biting your fingernails 'cause it's so gross.
It's also added to things like windshield wiper fluid,
which bizarrely tastes sweet.
So it's a good idea to add something that tastes gross
to stop kids drinking it, or adults drinking it.
There are even better molecules in plants
that aren't poisonous to humans.
For example, in broccoli and Brussels sprouts and green tea.
In fact, a lot of these bitter compounds
are actually good for us.
The reason we find the bitter is, again,
because the lock and key mechanism isn't good enough.
It's interesting that some people like a bitter taste
in some foods and that's testament to our big brains.
We're able to rationalize that some foods are good for us
and actually haven't poisoned us historically.
And we can override that repulsion instinct
from the bitter taste in those particular foods.
Actually, I have a hypothesis about certain bitter foods,
like coffee, chocolate, beer,
those all have psychoactive drugs
in them that are addictive, so it's no surprise
that we associate the bitter taste
in those things with a positive reward.
That's just my hypothesis though.
Plants are coming up with new ways
to protect themselves all the time
using chemicals, so there's quite
a bit of evolutionary pressure on the genes
that code for poison detecting receptors.
Because of this constant change,
you actually find that different people
have different bitterness receptors.
For example, you can buy tester strips
that have a chemical on them called PTC.
That's bitter for some people and not others.
For me, not bitter at all.
If you do taste bitterness on these tester strips,
then you're, what's called a super taster.
You have an additional bitterness receptor
that other people don't have.
Some scientists think there's a link
between whether you're a super taster
and whether you're going to enjoy
the taste of Brussels sprouts and broccoli.
If you're not a super taster, you're more likely
to be able to tolerate those foods.
Remarkably, these taste receptor cells
aren't just on our tongues, they're in our guts,
in our airways and in our urinary tracts as well.
It makes sense to have these receptors in our guts
because our guts need to know how to deal
with what we've put in there, like if there's a lot
of protein, release protease to break the protein down
into smaller chunks that we can absorb.
It also makes sense to have bitter receptors
in our stomachs, if any poisonous chemicals
do get past your tongue and end up in your stomach,
they will bind to those receptors and your stomach will know
that you've eaten something poisonous.
The way it responds is to delay the opening
of the stomach into the intestines.
And that gives your body time to respond to that poison,
perhaps to release a neutralizing agent,
or to make you throw up.
It also makes sense to have sugar receptors
in your intestines, like if you eat some sugar,
then some of those sugar molecules will bind
to the sweetness receptors in your intestines.
So, your body will know to release
some of those proteins that marshal
the sugar molecules into your bloodstream.
So, most of the sugar will be absorbed,
a little bit will be left behind.
But if you then consume some artificial sweetener,
those artificial sweetener molecules will also bind
to the sweetness receptors releasing even more
of those enzymes that will latch
onto any of the remaining real sugar
in your intestines and carry it into your bloodstream.
The upshot is that artificial sweetener may actually
cause your body to absorb more
of the real sugar that you eat.
That's not to say that artificial sweetener is bad for you
so long as you're using it in place of real sugar.
It's just that it's not as effective
as it would be if it weren't
for those pesky sweetness receptors in your intestines.
Some people pointed out that acid doesn't work quite
the way that I described, like in an acidic solution
I implied that protons were swimming
around on their own, these hydrogen ions.
But what really happens is they latch onto a water
and you get something called H3O+, or a hydronium ion.
So, is it right to say that protons tastes sour?
Well, actually I think it is
because when you're tasting sour things,
it's not hydronium ions that are entering gustatory cells
it's the protons, they get passed
from those hydronium ions down
through the channel on their own.
Also, that's just what happens when you dissolve things
in water, they interact with the water molecules
like sodium ions, for example,
are surrounded by a solvation shell.
Sugar molecules dissolved in water
have water molecules attached to them.
We don't refer to these things as new entities.
We just say sugar dissolved in water,
or hydrogen ions dissolved in water.
This isn't the first time I've talked
about sugar in a video, amazingly, sugar molecules
can rotate polarized light and they rotate light always
to the right and never to the left.
For an explanation, check out the link
in the card and the description.
By the way that berry that I talked
about at the start of the video
that tricks primates into eating them,
that doesn't work on gorillas anymore.
Gorillas have evolved and the receptor
that they have for sweetness
is a little different to everyone else's
and the trickster molecule doesn't bind to it,
which really shows that it's an evolutionary arms race.
There are so many more interesting things
to say about taste like, for example,
why can't cats taste sweet things?
Or how is it that miracle berries are able
to turn sour taste into sweet taste in your mouth?
All that stuff I'm gonna put in a separate video
that's an exclusive for my supporters on Patreon.
If you're interested in supporting me there,
the link is in the description.
I'm working on a video about neural networks.
So, I need to do a lot of learning around that.
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