Enzyme Catalysis Lab - Enzyme Catalysis Lab Jennie Chang...

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Enzyme Catalysis Lab Jennie Chang Period 6 AP Biology 14 October 2011
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Background Information: To sustain the life of a cell, certain chemical reactions are necessary to be carried out quickly and efficiently. Cells cannot rely on chance that random events might cause the necessary reaction to occur that will keep it alive and therefore, cells use enzymes to aid the process. An example of this is a disaccharide, a simple carbohydrate common in cells, composed of two units called monosaccharides. Monosaccharides are a major source of energy for cells; disaccharides and larger molecules called polysaccharides, are often taken in as nutrients for cells. Eventually, the polysaccharides will break down on their own, but not in time to support a cell’s life so that’s where enzymes come in. Enzymes are complex proteins that consist of one or more polypeptide chains, forming a specific shape crucial to substrate interactions—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 reactive with is called the substrate. The enzyme-driven reactions that occur spontaneously under the proper circumstances occur more quickly when enzymes act as catalysts. The enzymes allow these reactions to occur more efficiently by lowering the activation energy required to drive the reaction. Enzyme reactions can be affected by a variety of conditions such as environmental, including factors such as temperature, pH, and the concentration of the enzyme or substrate. When temperature rises, the average kinetic energy of any substance rises as well because the more heat added, the more molecular motion will occur. As a general rule, an increase of 10 ° C doubles the rate of most chemical reactions. This is true for enzymes as well but because enzymes are proteins, they are subject to heat-induced destruction of their tertiary structure, which is otherwise known as denaturation: the process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. Most enzymes require a neutral pH, while some work best in conditions that are extremely acidic or basic. An enzyme’s preference depends on the R groups of the active sites’ amino acids. Some enzymes will not be active until negative charges are neutralized. Also, enzymes follow the Law of Mass Action: the direction taken by an enzyme-catalyzed reaction is directly dependent on the relative concentration of enzyme, substrate, and product. When there is a great deal of substrate and little product, the reaction will form more product. Conversely, when there is a great deal of product and little enzyme, the reaction will form more substrate. Some reactions include exergonic reactions and endergonic reactions. Exergonic reactions, where
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Enzyme Catalysis Lab - Enzyme Catalysis Lab Jennie Chang...

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