Structural Model Of Jello On Molecular Level

Structural Model of JELL-O on Molecular Level Objective You will build a molecular-level model of how gelatin forms a soft elastic gel upon cooling. This model replicates on the macroscopic scale many of the properties of JELL-O (and thus of any gelatin) on the molecular scale.

Materials 1-5 packages of long pipe cleaners; the actual number needed depends upon number of students (these can be purchased in large packages from a craft store)

Procedure Each student should have ~20 pipe cleaners. Make a bundle with three pipe cleaners (call them strands) and twist them around each other 2-3 times to form right-handed braid; there should be pieces of arbitrary length hanging off each end of the braid. The three strands should be twisted tightly enough to hold together. Then take two more strands and twist them together with one of the strands hanging off the first braid, giving five pipe cleaners linked together by two righthanded braids. Or, take one more strand and twist it together with two of the hangin strands, giving you four pipe cleaners linked together. Continue this process with all of the pipe cleaners, randomly adding one or two pipe cleaners to your structure. Do not make a regular structure: be random and arbitrary (this is essential for the accuracy of the model.) Each student should then have a random “structure” composed of about 20 pipe cleaners linked together by twisted braids of three strands each. You should then begin to link together these individual structures by taking 3 strands (one from one structure and two from the other) and twisting them together as before. Continue this process until the class has made a single large structure. This structure should be irregular in shape and have approximately equal height, width, and depth. (Bend it back upon itself and make more braids to make this happen.) This irregular bundle of pipe cleaners is a good molecular model for JELL-O. Each individual strand (pipe cleaner) represents an individual polymer of the gelatin polypeptide. The twisted braids represent the triple helical crosslinks that hold gelatin together. These crosslinks form at low temperature; that is why gelatin gels in the refrigerator.

Discussion What are the properties of JELL-O (of gelatin): It jiggles: it is a soft solid that shakes when it is moved. It is soft: it does not take much effort to deform it. It is elastic: when you push on it, it springs back like a rubber ball. It supports its own weight even though it is mostly (99%) water. It is transparent. The model also has these properties Shake the model: it jiggles. Push on the model: it does not take much effort to deform it. Push on the model and let go: it springs back It supports its own weight even though it is mostly air. You can see through the model.

Amino acid structure in gelatin (collagen) polymer.

Space filling model of molecular structure of gelatin triple helix.

Model for dissolution and gelation of gelatin in water.