Photosynthesis.
The process by which plants, algae, and some bacteria
turn sunlight into energy, powering pretty much everything
on Earth.
But if we contained the same pigments that they do,
could we photosynthesize, too?
If you ate a lot of kale, could you go out in the sun
and sunbathe and make your own energy?
Well, for awhile now, scientists have
thought that one species of sea slug, elysia timida,
could do just that.
Naturally pale, the slug extracts
photosynthesizing organelles, known as chloroplasts,
from the algae that it eats.
And stores them in its body, turning
the slug a rather fetching shade of green.
Researchers found that these slugs could last for months
without food, leading them to believe that they were using
the extracted chloroplasts to make
their own food from sunlight, and photosynthesize themselves.
However, a little more recently, some more skeptical scientists
took these slugs and put them in the dark with no food.
And found that after months, the slugs were still alive.
Which is weird, because if they were actually
surviving by using the chloroplasts to make food
from light, then in the dark they
should have died with no food.
So without light, there was no way
that these guys could be photosynthesizing.
But there were some problems with this idea, anyways.
Chloroplasts don't just exist in a vacuum.
They require lots of other accessory molecules
from the rest of the algal cell that surrounds them.
And it was highly unlikely that the slug
could be producing these same needed
molecules for the chloroplasts.
It was hypothesized that along with the chloroplasts,
these slugs might be taking up some DNA
from the original algal cells, too.
And then using that to produce the needed proteins.
But as more research was done, this
looks to be pretty unlikely.
So those photosynthesizing sea slugs
are probably not photosynthesizing at all.
OK.
So then why did I bring this up anyways?
Well, because there's a paper that came out recently
in the Journal of Cell Science that
indicates and suggests that perhaps mammalian tissues,
you know, like us, we're mammals,
might be able to take up not the chloroplasts themselves,
but broken down pieces, or metabolites, of chloroplasts
that we eat.
And then put them into our tissues.
And then use them to photosynthesize.
It's crazy.
I know.
But I think it's an interesting paper.
So let's step through it.
So the researchers hypothesized that maybe
the broken down metabolites of these chloroplasts
could travel to cells in the mammalian body.
And there, work with the mitochondria in those cells.
Now mitochondria, if you remember,
are sort of the powerhouses of the cells.
They produce cellular energy in the form of ATP.
So the first thing the researchers did was they
took these broken down chlorophyll metabolites,
and they mixed them with mouse liver mitochondria.
They then exposed this mixture to light
and judged how much ATP was produced.
And they found, surprisingly, that mitochondria
mixed with this metabolite and exposed to light,
produced more ATP than mitochondria alone that
were exposed to light.
Very interesting.
Next, to replicate what might happen
with sort of normal mitochondria levels in a tissue,
they took mouse brains, homogenized them,
mixed them with this metabolite, and then put a light on them.
And once again, they found that there
was more ATP produced when the mouse brains were mixed
with this metabolite and had a light shone on them, then when
the mouse brains were just exposed to light on their own.
Very strange.
But in a real animal, these metabolites wouldn't just
be mixed up with the tissue, they
would have to travel there through the digestive system.
So next, researchers fed mice a chlorophyll rich diet.
And then looked for chlorophyll metabolite-like fluorescence
in tissue samples from the body to see whether or not
these metabolites could be broken down in the stomach
and then distributed into tissues.
And what they found was actually that they
could see this chlorophyll-like fluorescence in the brain,
and in fat, and in some gut tissues.
Which is really pretty crazy.
The researchers also found that this chlorophyll-like
fluorescence localized to the mitochondria.
As their hypothesis suggested that they would.
And they also went on to do a whole lot of biochemical assays
to see whether or not this extra ATP produced in these samples
would actually be coming through biochemical pathways related
to photosynthesis.
And their findings did support their hypothesis
that these chlorophyll-derived pigments might be
traveling to the mitochondria.
And somehow working with the mitochondria
to turn the light into energy.
It's really crazy.
So do I buy it?
May be.
I think the idea is really cool.
And I think they've got some really
cool preliminary findings.
But I noticed in the paper that they
said that they found these chlorophyll-like pigments
traveling to brain tissue, and fat tissue, and gut tissue.
But they didn't mention anything about the skin.
Which is actually the tissue that
is most exposed to light in the mammalian body.
Now they did make the argument that light does travel
through your skin and through your skull.
And they actually made the very interesting point
that on a clear day, the amount of light illuminating
your brain would allow you to comfortably read
a printed book.
Which, OK.
All right.
That's a lot of light traveling through.
But I wonder if it would be enough really
to make any sort of noticeable difference,
if in fact these chlorophyll-like pigments were
working with the mitochondria to produce any energy.
Would the ATP that they produced even be
relevant on a biological scale?
I mean, how much chlorophyll would you
have to eat to actually get enough of these pigments
to your mitochondria to make a difference in the amount of ATP
that they produced?
They also found a really weird result in that first test
where they mixed straight mitochondria
with this metabolite, that if they
added too much of the metabolite,
the ATP production actually dropped
back down to baseline levels.
Which is weird.
You would think if you added more of this pigment,
you would either reach some sort of plateau of ATP production,
or ATP production would keep increasing.
But they found that if you added too much chlorophyll
it went back down.
And that seems kind of sketchy to me.
So am I going to go out, and eat a big salad,
and lie out in the sunlight, and get all my energy that way?
No.
And I don't think you should, either.
But do I think that this is a really cool hypothesis
and some interesting preliminary findings that
should be looked into more?
Yeah.
I think I do.
Go forth.
Do science.
And eat your vegetables.