Defined Words: enzymes, active site
Enzymes are large proteins that are formed usually by cells. I say “usually” because enzymes present us with an updated chicken and egg dilemma. Enzymes are proteins that aid in cell functioning, including the manufacturing of proteins, like enzymes. So the question is: if cells require enzymes in order to make enzymes, where did the first enzymes come from? We currently don’t have an answer to this riddle, but we know that enzymes exist so we’ll look at them from a top-down perspective.
The main purpose of enzymes is to lower the overall energy needed to perform specific reactions. Each enzyme is very particular about which molecules are able to bind to the active site of the enzyme. The active site is the term we use for the section where the reaction occurs. Enzymes have a small cavity that is lined with specific amino acids that can bind onto reactant molecules and let go of the products. A reaction with an enzyme has a much better chance of taking place since the reactant molecules are held in a position that allows for the exchange of electrons.
You can think about enzymes as that “matchmaker” friend that you either know or have seen on TV. The matchmaker goes around a party and encourages relationships to form among people who are talking or even just nearby. Similarly, the enzyme approaches reactant molecules and “encourages” them to react by holding them in place.
Enzymes can aid in the building of larger molecules or in the breakdown of particles into smaller pieces. You secrete a bunch of enzymes in your saliva that help to start the digestion process before the food even reaches the stomach. In the stomach, enzymes break apart the remainder of the food. Stomach acid also helps in this breakdown but its main purpose is to establish the optimum pH for the enzyme activity.
Reactions sometimes require an addition of energy: more movement of molecules allows for a greater chance of the reactants to run into each other. However, with the use of enzymes, the same reactions can take place much more efficiently with significantly less energy required. This means that enzymes can allow for processes that aren’t energetically favorable at every step.
Let’s look at an example. Glycolysis, the process of breaking down sugar for energy, is a multi-step reaction. Overall the reaction is energy releasing but several of the steps require energy to be absorbed and are therefore energetically unfavorable. Enzymes meant that those energy needing steps were much more likely to occur.
You are in contact with enzymes throughout your daily life and you might not even know it. Scientists have discovered a way to use the reactive power of enzymes to clean, ferment plants for fuel or beer, even synthesize food. Soap is the most commonly used enzyme-based product, and it is so concentrated that you only need a fraction of what you’ve probably been using. After all, the enzymes can team up with water, the Universal Solvent, to clean anything.
The development of enzymes was certainly a progress boost in our history. Cells did not have to follow the laws of energy to the letter. Those cells could allocate more energy toward other aspects of the struggle to stay alive. Leave it to life to defy the laws of physics and energy. Humans continue to defy the rules that said we couldn’t control the electron or fly to the moon. I like to think that we mimicked the defiance of our enzymes. In that defiance, we’ve done incredible things.