About Alexander Expertise I can answer questions regarding all materials taught up to AP Chemistry and a majority of organic chemistry. This includes elementary, high school, and some college level chemistry. I can answer questions regarding stoichiometry, reactions, gases, thermodynamics, atomic structure and periodicity, bonding, chemical kinetics, acids and bases, spontaneity, entropy, and free energy, electrochemistry, and organic and biological molecules.
I cannot answer advanced organic chemistry questions, or questions involving a high level of physics involved. Other than that, I can answer ultimately any question you have.
Experience PHD in Chemistry from William and Mary college in VA. High school teacher of all level for 30 years.
Organizations Flynn Sciences
Publications Numerous science catalogs, an instructional Lab Kit book for lab procedures.
Question My children did an experiment to observe enzyme action using raw pineapple pulp and jello. They mixed one sample with the raw pulp and one sample with pulp that had been heated for 5 minutes. I know why heating the pulp changed the reaction, but I don't know how the enzyme works. If an enzyme is a catalyst and a catalyst increases the rate of a reaction, why does the enzyme prevent the jello from hardening?
Answer Hello Max!
The pineapple-jello lab is a classic. Here's what's going on:
Gelatin is made from a protein called collagen, found in the joints of animals. Gelatin can be dissolved in hot water. As the dissolved gelatin cools, the collagen forms into a matrix that traps the water. The result of this process is the jiggling, semi-solid mass that we all know as Jello.
Pineapple (as well as kiwi, papaya, and figs) belongs to a group of plants called Bromeliads. The enzyme in pineapple juice that is responsible for
the breakdown of collagen is bromelin. The process of canning pineapple denatures
the bromelin, rendering it incapable of catalyzing the break down of gelatin. When you heat the pineapple juice, you are denaturing the bromelin enzyme, thus preventing not only a catalysis but moreover the matrix forming, cooling period that would normally produce Jello.
