UCSB Science Line (2024)

As you may recognize from the commercials, Jell-Ois basically a brand name for gelatin (with sometype of sweetener, flavoring, and coloring).

Gelatin, which is processed form of collagen, isthe ingredient of Jell-O that gives it thatsemisolid texture when it is cooled down. Youcan imagine gelatin as three amino acid chains(polypeptide chains) that wind around each otherin a helical structure. Specifically, the threechains wrap around each other in a triple helixstructure. (To visualize this, imagine - or lookup - the "classic" double helix structure of DNA,and then imagine a third chain also winding aroundwith it.) Much like in DNA, the three chains areweakly bound together through interactions betweenthe different parts of the amino acids.

When thegelatin is heated in water, those weak bonds breakand the polypeptide chains become free anddisordered. When the gelatin solution cools, thechains begin to re-associate with each other. However, instead of reforming a perfect triplehelix when the chains associate with other chains,drops of liquid get trapped between thepolypeptide chains. Thus Jell-O is simply thisnetwork of trapped liquid in protein chains.

Jell-O is made out of something called gelatin (itis pronounced like jell-atin). Gelatin is aprocessed form of a kind of protein found inanimals. If you don't already know, every livingthing is made almost entirely out of proteins (andlots of water!).

Gelatin has a veryparticular structure: It is made out of threesmaller fibers that are wrapped around each otherlike a long rope. The smaller fibers like tobe attached - that's what keeps them wrappedaround each other. When you heat up some gelatinmixed into water, the water molecules bump intothe fibers a lot and cause them to come apart. That is the liquid form of jell-o.

Whenthe jell-o cools down again, the fibers come backtogether...sort of. It turns out that when thefibers come back together, they end up beingtangled up. That's because, though the fiberswant to be attached to each other, they don't careif they are attached to the same fiber all the waydown their length (the way they started) or lotsof different fibers. They just want to touch asmany other fibers as possible. In your body, Ithink there are other proteins that make sure allthe fibers combine properly but in jell-o, all thedifferent fibers get tangled into a big net. Thewater gets trapped between all the fibers and theresult is something that acts a little bit like asolid. It is usually called a "gel", though.