This week in AP Bio, we had a short week and began to cover enzymes. Enzymes are proteins, which are made up of amino acids. They are used to catalyze chemical reactions. We learned that they are good because they can lower the activation energy of a reaction which basically makes it easier and can speed up the process. Enzymes are NOT consumed in the reaction, they are just there to speed up the reaction.
Enzymes have what is called an active site (pretty much a hole in the enzyme), which is filled by what is called the substrate. The substrate fits perfectly, the video referred to it as lock and key (although Mr. Dunn didn’t like that metaphor). When the substrate is inside of the active sight there is a “chemical tug” which lowers the activation energy and can break it into products. Enzymes can be both turned on, and turned off. There are two ways to turn an enzyme on, you can just not produce them until they are needed, or you can activate them. To activate them, you add something to the enzyme to make it do what it needs to do. There are Cofactors and Coenzymes. Cofactors are small inorganic chemicals that contain no carbon. Cofactors are organic and they do contain carbon. To turn enzymes off, we can use inhibition. There are two types of inhibition, the first one is called competitive inhibition, which is when you use an inhibitor (a chemical of some sort) to block the active site and deny any substrate from getting in. The second type of inhibition is Allosteric inhibition (or non competitive inhibition). Allosteric inhibition is when the inhibitor bonds to what is called the allosteric site which then covers up the active site. This makes it impossible for the substrate to get in. Another type of Allosteric inhibition is when the inhibitor goes to the allosteric site but doesn’t block it, instead it changes the shape of the active site. If the active site doesn’t perfectly fit the substrate, it won’t go in.
To represent this in class and try to gain a better understanding, we did a lab involving toothpicks. The idea being that there are 100 tooth picks in a bowl, without looking, you are meant to reach in and break as many toothpicks as you can. The catch being that you can’t break a toothpick that is already broken, and you never replenish the number of toothpicks. Theoretically the rate of toothpicks being broken should get slower and slower because there are less whole toothpicks to break. We did the lab a second time, but this time we were supposed to change something about the experiment. Our group chose to have me break the toothpicks with only my left hand instead of both hands. The experiment should have worked on paper, the issue with our experiment was the human error. At first I was very slow at breaking the toothpicks, but later on I was breaking them much faster even though there were less and less toothpicks available to break. I guess I adapted, too bad this wasn’t for the evolution unit. While our graph should have increased less and less gradually, I instead got a graph that went up and up and up.
What we wanted. What we got.
Well…. At least we tried