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[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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