Enzyme Catalysis Pre-Lab Background
Enzyme Structure and Function
Certain chemical reactions, necessary to sustain the life of a cell, must be carried out quickly and efficiently. A cell cannot depend on the possibility that random events will cause the necessary reaction to occur that will keep it alive; therefore, cells employ a particular molecule, called an enzyme, to aid in the process. For example, a disaccharide, a simple molecule that is a carbohydrate common in cells, is composed of two units called monosaccharides. Monosaccharides are a major source of energy for all cells; but disaccharides and larger molecules called polysaccharides, which are made up of three or more monosaccharides, are commonly taken in as nutrients. Eventually the molecules would break down into monosaccharides on their own, but not in time to support a cell’s life. Therefore, cells utilize an enzyme that can cause a particular molecule to break apart or come back together. These enzymes are complex proteins that consist of one or many polypeptide chains, forming a shape crucial to the kinetics of enzyme-substrate interactions.
For an enzyme to be specific, it must fit over a molecule. The portion of the enzyme that fits over the molecule is called the active site. The molecule that the active site is reacting with is called the substrate. When the enzyme is reacting with the substrate, a complex is formed. This interaction can be expressed as:
Some enzymes change shape after binding to a substrate, improving the “fit” between the enzyme and the substrate. This new formation is called the “induced fit model”. (See above) Note: An enzyme is a protein molecule that catalyzes specific metabolic reactions without itself being permanently altered or destroyed. A substrate is a substance acted upon by an enzyme. Note that in the above reaction, the arrows go in both directions. This illustrates the principle of...