enzyme catalysis, Science, College Term Papers.com


		Data Bases
		• Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism?

		Links
		• Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com

		Free Essays
		• Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers

Search Lots of Essays

Back to Subjects - Science

enzyme catalysis

enzyme catalysis In essence, the main objective was to use chemical titration to measure and then calculate the rate of conversion of hydrogen peroxide (H2O2) to water and oxygen by using the enzyme catalase. Other purposes of the lab were; to measure the effects of changes of temperature, pH, enzymes concentration, and substrate concentration on rates of an enzyme. The lab was also an opportunity to see a catalyzed reaction in a controlled experiment. And the last objective was to learn how environmental factors affect the rate of enzyme catalyzed reactions. Enzymes are proteins produced by living cells. They act as catalysts in biochemical reactions. A catalyst speeds up the rate of a chemical reaction and makes it possible for the reaction to occur with a lower initial input of energy. One benefit of enzyme catalysis is that the cell can carry out complex chemical activities at a relatively low temperature (AP Lab Manual). In biochemical reactions, the enzyme, E, combines reversibly with its specific substrate, S, to form a complex ES. One result of this temporary formation is a reduction in the energy required to activate the reaction of the substrate molecule so that P, the products of the reaction are formed. In summary: E+SESE+P. The enzyme is not changed in the reaction and can break down additional substrate molecules (Lab Bench). The enzyme used in this lab is catalase. Catalase has a molecular weight of approximately 240,000 daltons and contains four polypeptide chains, each composed of more than 500 amino acids. This enzyme occurs universally in aerobic organisms. One function of catalase within cells is to prevent the accumulation of toxic levels of H2O2 which is formed as a by-product of metabolic processes. Catalase might also take part in some of the many oxidation reactions going on and in all cells (AP Lab manual). The primary reaction catalyzed by catalase is the decomposition of H2O2 to form water and oxygen: 2H2O22H2O+O2 (gas). This reaction occurs spontaneously, but not at a very rapid rate. Catalase speeds up the reactions moderately. In this experiment, we determined a rate for this reaction (AP Lab Manual). We hypothesized that the rate of a reaction is determined by measuring the accumulation of one of the products or by measuring the disappearance of the substrate. We also hypothesized that the rate of the reaction is the slope of the linear part of the graph that describes the accumulation of product (or decrease in substrate) as time progresses. We based this reasoning on our knowledge of the standards of graphing. And lastly, we hypothesized that the reaction rate may be affected by temperature, pH, and activations and inhibitors. A description of several ways enzyme action may be affected follows: 1. pH. Amino acid side chains contain groups such as - COOH and NH2 that readily gain or lose H+ ions. As the pH is lowered an enzyme will tend to gain H+ ions, and eventually enough side chains will be affected so the enzyme's shape is disrupted. Likewise, as the pH is raised, the enzymes will lose H+ ions and eventually lose its active shape. Many of the enzymes function properly in the neutral pH range and are denatured at either an extremely high or low pH. Some enzymes, such as pepsin, which acts in the human stomach where the pH is very low, have a low pH optimum (Enzyme Catalysis). 2. Temperature. Generally, chemical reactions speed up as the temperature is raised. As the temperature increases, more of the reacting molecules have enough kinetic energy to undergo the reaction. Since enzymes are catalysts for chemical reactions, enzyme reactions also tend to go faster with increase temperature. However, if the temperature of an enzyme-catalyzed reaction is raised still further, a temperature optimum is reached; above this value the kinetic energy of the enzyme and water molecules is so great that the conformation of the enzyme molecules is disrupted. The positive effect of speeding up the reaction is now more than offset by the negative effect of changing the conformation of more and more enzyme molecules. Many proteins are denatured by temperatures around 40-50 degrees C, but some are still active at 70-80 degrees C, and a few even withstand boiling (Enzyme Catalysis). 3. Activation's and Inhibitors. Many molecules other than the substrate may interact with an enzyme. If such a molecule increases the rate of the reaction it is an activator, or if it decreases the reaction rate it is an inhibitor. These molecules can regulate how fast the enzymes act. Any substance that tends to unfold the enzyme, such as an organic solvent or detergent, will act as an inhibitor. Some inhibitors act by reducing the -S-S- bridges that stabilize the enzyme's structure. Many inhibitors act by reacting with the side chains in or near the active site to change its shape or block it. Many well known poisons such as potassium-cyanide and curare are enzyme inhibitors that interfere with the active site of critical enzymes (Enzyme Catalysis). Bibliography: References: "Enzyme Catalysis" sc2000.net. 1page. 21, Feb. 2002 "Lab Bench: Enzyme Catalysis" Biology.com. Pg. 1-3. 21, Feb. 2002 http://www.biology.com/learning/enzyme/concepts.html AP biology lab manual (appropriate reference and date N/A)

Word Count: 833