As you may recognize from the commercials, Jell-O
is basically a brand name for gelatin (with some
type of sweetener, flavoring, and coloring).
Gelatin, which is processed form of collagen, is
the ingredient of Jell-O that gives it that
semisolid texture when it is cooled down. You
can imagine gelatin as three amino acid chains
(polypeptide chains) that wind around each other
in a helical structure. Specifically, the three
chains wrap around each other in a triple helix
structure. (To visualize this, imagine - or look
up - the "classic" double helix structure of DNA,
and then imagine a third chain also winding around
with it.) Much like in DNA, the three chains are
weakly bound together through interactions between
the different parts of the amino acids.
gelatin is heated in water, those weak bonds break
and the polypeptide chains become free and
disordered. When the gelatin solution cools, the
chains begin to re-associate with each other.
However, instead of reforming a perfect triple
helix when the chains associate with other chains,
drops of liquid get trapped between the
polypeptide chains. Thus Jell-O is simply this
network of trapped liquid in protein chains.
Jell-O is made out of something called gelatin (it
is pronounced like jell-atin). Gelatin is a
processed form of a kind of protein found in
animals. If you don't already know, every living
thing is made almost entirely out of proteins (and
lots of water!).
Gelatin has a very
particular structure: It is made out of three
smaller fibers that are wrapped around each other
like a long rope. The smaller fibers like to
be attached - that's what keeps them wrapped
around each other. When you heat up some gelatin
mixed into water, the water molecules bump into
the fibers a lot and cause them to come apart.
That is the liquid form of jell-o.
the jell-o cools down again, the fibers come back
together...sort of. It turns out that when the
fibers come back together, they end up being
tangled up. That's because, though the fibers
want to be attached to each other, they don't care
if they are attached to the same fiber all the way
down their length (the way they started) or lots
of different fibers. They just want to touch as
many other fibers as possible. In your body, I
think there are other proteins that make sure all
the fibers combine properly but in jell-o, all the
different fibers get tangled into a big net. The
water gets trapped between all the fibers and the
result is something that acts a little bit like a
solid. It is usually called a "gel", though.
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