The Energy Barrier for a Chocolate-Craving Pregnant Woman

Written by Kelly A. Hogan, University of North Carolina at Chapel Hill

When discussing the energy of activation (EA) related to enzymes, I tell students about when I was pregnant and ate ice cream every night. I explain that after dinner I would sink into my deep, fluffy sofa. When I deemed it ice cream time, it was challenging to get up to get from the sofa with a big belly. I would complain and huff and puff,  etc. But sometimes, my lovely husband would hold his arm out and help to pull me off the sofa. In this analogy, my husband is the enzyme (catalyst) because he lowered the energy barrier for me. However, he didn’t make the impossible happen—I would have gotten that ice cream on my own—he just made it easier and faster for me to be a happy pregnant woman full of ice cream (the product of the reaction).