Enzyme structure, activation energy and inhibition

Created March 2020, Offline version here
Video by Paul Anderson, also on his website Bozeman Science.

    Enzymes are made of and are crucial to cellular function. As every organism undergoes numerous chemical reactions, they need some chemical help so that the chemical reactions happen at an effective rate. Enzymes work by the activiation energy required for the chemical reaction to start. If you think of a chemical reaction as a giant hill and you are on a bicycle trying to ride your bike over that hill, wouldn’t it help if the hill decreased in size so you do not have to spend as much energy? That is what enzymes do. By the amount of energy required for the chemical reaction to start, the reaction is “speed up”.
    The general function of an enzyme is to breakdown larger molecules into smaller ones. The molecule in need of breakdown is known as the substrate, which is also the reactant in the chemical reaction. Enzymes have an area called the where the substrate binds to it for the chemical breakdown to begin. It is important to note that the enzyme is not listed in the chemical reaction, therefore the enzyme is not “used up” unlike the reactants.
    An example of a molecule breakdown reaction is the breakdown of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2) molecules. 2H2O2 → 2H2O + O2 Catalase, the enzyme that helps with this process, takes the reactant, hydrogen peroxide, as the and binds it to the active site.
    After the bond between the substrate and active site is secured, the enzyme works to break the bonds of the substrate and form the of the chemical reaction. The products are then released from the substrate-enzyme complex.
    The relationship between substrate and enzyme is very specific in that there is a specific pairing between enzyme and substrate. One enzyme cannot catalyze different reactions. For instance, catalase can only breakdown , not anything else.
    With this unique relationship, the idea of a key and lock fit is used to model this. Where the enzyme models the and the substrate models the .
    As you can imagine, there are numerous chemical reactions that occur in organisms to maintain life. With this, the number of enzymes is also numerous as enzymes can only carry one job. To keep efficiency in cell, the cell has regulatory processes to where the enzyme is manufactured as required. In addition to the cell’s regulatory processes, the enzyme also has its own way to regulate itself. The two ways enzyme can control its function is through activators and inhibitors. Activators turn the enzyme “ ” so that it functions, and inhibitors turn the enzyme “ ”.
    There are two types of activators that bind to the enzyme: cofactors and coenzymes. Both are needed for normal function of the enzyme. The chemical difference between the two is that cofactors are made up of molecules, or molecules that are not carbon-based.
    Coenzymes are made up of molecules, or molecules are carbon-based.
    Inhibitors are molecules that “inhibit” or “stop” the function of the enzyme. These molecules can either bind to the active site or the allosteric site on the enzyme and this depends on the type of inhibition. is where the inhibitor molecule and the substrate “compete” for the active site. When the inhibitor molecule binds to the active site, that space is taken up which causes the substrate to have nowhere to bind to hence stopping the enzyme function.
    The non-competitive inhibition is called where if the inhibitor binds to the enzyme, it changes the shape of the active site. This causes the substrate to be unable to bind to the active site due to the conformational change.
    As enzymes are made of proteins, any physical or chemical change that affect proteins will affect the enzyme function. Such physical change may be temperature related. Too high or too low of a temperature in the environment may affect enzyme function. Chemical change may be pH related where if the environment is too acidic or basic may cause the enzyme to malfunction.
    In summary, enzymes help catalyze or speed up chemical reactions by lowering the activation energy required. The substrate (reactant) binds to the active site on the enzyme so that the enzyme can break down the substrate into smaller molecules. Once the larger molecule is broken down, the product is released. To control and regulate the enzyme function, enzymes have activators and inhibitors to turn the enzyme on or off. There are two types of activators: cofactor and coenzyme. Cofactors are made up of inorganic molecules and coenzymes are made of organic molecules. There are two ways enzymes are inhibited: competitively and allosterically. Competitive inhibition is where the substrate and the inhibitor molecule compete to bond to the active site. Allosteric inhibition is where the inhibitor molecule binds to an allosteric site, not the active site, and causes the active site to change its shape so that the substrate can no longer bind to it.