applications anJ analoqies Enzyme Activity :ASimple Analogy Kenton B. Abel and Donald R. Halenz Pacific Union College Angwin, CA 94508
Beginning biochemistry students oRen have a hard time understanding enzyme activity and how inhibitors and variations in temperature, enzyme concentration,and substrate wncentration affect reaction rates. This may stem largely from the student's inability to relate with something so small, (wmpared to the student) or molecules as complex as enzymes. Presented here is a simple analogy that has helped students in our classes grasp the wncept of enzyme activity. Imagine a child (representing an enzyme)with a pin popping balloons (representing the substrate) in a gym. If there were one child and a balloon every 10 feet, not many balloons would get popped per sewnd. As more balloons were added to the gym,the child wouldn't need to run as far between balloons and so the popping rate would increase. If the child were waist deep in balloons, he would be popping balloons as fast as he could so adding more balloons would no longer increase his popping rate. (The child would be a t his V,,,,.) If another child were put in the gym, twice as many balloons would be popped per second. Likewise, four children could pop four times as many balloons per sewnd as one child.
RONDELORENZO edited by Middle Georgia College Cachran, GA31014
Say that there was one child popping balloons at 30 "F. He would be shivering much of the time and not popping as many balloons as possible. As the temperature of the gym increased to around 70 "F, the child would be close to his optimum temperature and merrily popping away. But how many balloons would the child be popping at 212 O F ? Obviously none. He would have passed out from the heat. (Denaturation.) Inhibitors a r e commonly broken down into two categories: irreversible and reversible. Irreversible inhibition is analogous to what happens if the child dies. (After all, from the enzyme's point of view, this is what happens to it when heavy metals are added or when cyanide binds to cvtochmme oxidase.) F& reversible inhibition there are two major types, comnetitive and noncompetitive. Competitive inhibition occurs &hen some of the balloons are made of thick rubber and won't pop. The number of balloons popped per second would depend upon how many normal balloons there were and how many thick rubber balloons there were. Noncompetitive inhibition would be to handcuff the child's hands behind his back for a portion of the time. When he was handcuffed, he wouldn't pop balloons. But whenever the child was not handcuffed, he would continue to pop balloons. The students in our classes have been able to relate much better with a child popping balloons than to an enzyme acting on a substrate. The two situations are similar. This analogy has helped students gain a better understanding of the concepts involved in enzyme activity.
Volume 69 Number 1 January 1992
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