Enzymes are very specific and only work with certain substrates. For example: Maltose is made of two glucose molecules bonded together (1). The maltase enzyme is a protein that is perfectly shaped to accept a maltose molecule and break the bond (2). The two glucose molecules are released (3). A single maltase enzyme can break in excess of 1,000 maltose bonds per second, and will only accept maltose molecules. Enzymes have extremely interesting properties that make them little chemical–reaction machines.
The purpose of an enzyme in a cell is to allow the cell to carry out chemical reactions very quickly. These reactions allow the cell to build things or take things apart as needed. This is how a cell grows and reproduces. At the most basic level, a cell is really a little bag full of chemical reactions that are made possible by enzymes!
Enzyme Lactase is essential to complete digestion of whole milk. Lactase breaks down lactose, a complex sugar which gives milk its sweetness. Lacking lactase, a person consuming dairy products may experience the symptoms of lactose intolerance. Enzymes are large biological molecules responsible for the thousands of chemical interconversions that sustain life. They are highly selective catalysts, greatly accelerating both the rate and specificity of metabolic reactions, from the digestion of food to the synthesis of DNA. Enzymes are the sparks that start the essential chemical reactions our bodies need to live. They are necessary for digesting food, for stimulating the brain, for providing cellular energy, and for repairing all tissues, organs, and cells.
Enzyme–substrate specificity: A substrate is a reactant molecule which binds to an enzyme. A particular enzyme typically reacts with specific substrate which is called enzyme–substrate specificity. When a substrate binds to an enzyme, the enzyme catalyzes the chemical reaction by converting the substrate to end product. One of the important properties of enzymes is its specificity, they exhibit relative to the reactions they catalyze. Few enzymes are absolute specific; that they catalyze only one particular reaction. Other types of enzymes may be specific for a particular type of chemical bond or functional group.
For example: You may have heard of people who are lactose intolerant, or you may suffer from this problem yourself. The problem arises because the sugar in milk – lactose – does not get broken into its glucose components. Therefore, it cannot be digested. The intestinal cells of lactose–intolerant people do not produce lactase, the enzyme needed to break down lactose. This problem shows how the lack of just one enzyme in the human body can lead to problems. A person who is lactose intolerant can swallow a drop of lactase prior to drinking milk and the problem is solved. Many enzyme deficiencies are not nearly so easy to fix.
Thus, there are hundreds or millions of copies of each different type of enzyme, depending on how important a reaction is to a cell and how often the reaction is needed. These enzymes do everything from breaking glucose down for energy to building cell walls, constructing new enzymes and allowing the cell to reproduce. Enzymes do all of the work inside cells.