[MUSIC PLAYING]
Hi.
I'm Lauren Vogelbaum.
This is Brain Stuff.
And today's question
is, why do apples
turn brown when you slice them?
And what can we do
to prevent that?
All cells, whether they are
bacteria cells, human cells,
or apple cells, contain
thousands enzymes.
These enzymes catalyze all
of the chemical reactions
necessary to keep a
cell, or therefore,
a whole human person alive.
When you slice
into an apple, you
open up some of those cells.
Well, one of enzymes
there, tyrosinase,
does its thing when it
encounters oxygen, which there
happens to be a little
bit of in the air.
So the thing that does?
It turns fruit brown.
The easiest way, therefore,
to prevent browning
is to put your apple
slices in water
so that the tyrosinase
doesn't have access to oxygen.
You can also add a little bit
of something with ascorbic acid,
like lemon juice, and that
will inactivate the enzyme.
Now in human cells, we
also have tyrosinase.
It's what helps
create melanin, which
is what in turn gives color
to our skin, hair, and eyes.
Now in our skin, it
also helps protect us
from the harmful
UV rays of the sun.
So in humans, the browning
that tyrosinase causes
is actually a good thing.
That's assuming
that you can tan.
I kind of burn, and then
peel back to translucent.
In conclusion, wear sunscreen.
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