B.11B_Enzymes_onlevel – 03

The reactant, or substrate, binds temporarily to a special area on the enzyme molecule called the active site. When the substrate binds, the active site changes slightly to better fit the substrate. This action is similar to the slight adjustment of your grip when shaking another person’s hand. The slight adjustment places the substrates into the correct position needed for the reaction to take place.

The bonds of the substrates are stretched and strained. This weakens the bonds of the substrate and lowers the amount of energy needed to convert substrates to products. The products break away from the enzyme. The active site is now free for another substrate to temporarily bind to it and repeat the process.

Enzymes are usually large protein molecules folded into very specific 3D shapes. The function of the enzyme is dependent on its structure. The specific shape of an enzyme makes it suited for only certain reactants to bind to it. The enzyme is specific for a reactant just as a lock is specific to a key. For example, the enzyme that breaks down lactose will not break down the very similar sucrose and maltose molecules.

The lactase enzyme is specific for the reaction that breaks down the lactose molecule into simple sugars that can be used by cells.  Lactase is produced in the small intestines of humans and other mammals.  Lactase molecules are uniquely shaped to fit only lactose molecules.  When mammals drink milk, lactase enzyme that is produced in the small intestines helps to break down the lactose in the milk. 

People who are lactose intolerant do not produce enough lactase to break down the lactose in the dairy products that they eat and drink. The lactose molecules cause abdominal discomfort as they make their way through the digestive system. The lactase enzyme in Ben’s pill breaks down lactose in the same manner as naturally produced lactase. This prevents the abdominal pain and discomfort associated with lactose intolerance. It also allows Ben’s cells to take in the important simple sugars that are  produced when lactose is broken down.

There are many inherited disorders that are caused by lacking an enzyme or enzymes that do not function properly. Some of the disorders, like lactose intolerance, are caused by a lack of enzymes that break down foods or convert nutrients into useful energy. These disorders rob the organism of important energy molecules and raw materials to build more cells. There are other inherited disorders that involve lack of enzymes that break down metabolic wastes or other biomolecules. Over time, harmful quantities of the molecules build up in cells, tissues, and organs.

Enzymes can be found in all cells of organisms. They are important biomolecules with very specific structures that provide very specific functions. They allow chemical reactions to occur quickly under the normal, steady-state conditions in an organism. Enzymes are vital components of every cellular process.