Catalase Lab Activity-SA.rev

Catalase Lab Activity-SA.rev - Anandan BIO122A Fall 2010...

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Anandan BIO122A Fall 2010 Introduction to Enzymology: Catalase * 1. The purpose of this project: For the first 4 weeks of BIO 122 you will learn about the enzyme catalase in the lab. This laboratory practical is aimed at getting you acquainted with enzymes and enzyme kinetics. In addition, the written project proposal and final lab report are designed to develop your scientific writing skills. This project is also designed to help develop your skills in building and maintaining a scientific research collaboration with the members of your lab group. 2. What are enzymes ? Why are they important ? What do they do ? How do they carry out their functions ? Enzymes are biological catalysts that carry out thousands of chemical reactions that occur in living cells. They are generally large proteins made up of several hundred amino acids, and often contain a non-proteinaceous group, called the prosthetic group, that is important in the actual catalysis. In an enzyme-catalyzed reaction, the substance to be acted upon, or substrate , binds to the active site of the enzyme. The enzyme and substrate are held together in an enzyme-substrate complex by hydrophobic bonds, hydrogen bonds and ionic bonds. The enzyme then converts the substrate to the reaction products in a process that often requires several chemical steps, and may involve covalent bonds. Finally, the products are released and the enzyme is ready to form another enzyme-substrate complex. As is true of any catalyst, the enzyme is not used up as it carries out the reaction, but is recycled again and again. One enzyme molecule can carry out thousands of reaction cycles every minute. Each enzyme is specific for a certain reaction because its amino acid sequence is unique and this engenders a unique three-dimensional structure. The business end of the enzyme molecule, the active site, also has a specific shape so that only one or a few of the thousands of compounds present in the cell can productively interact with it. Any substance that blocks or changes the shape of the active site will interfere with the activity and efficiency of the enzyme. If these changes are large enough, the enzyme can no longer act at all, and is said to be denatured and this is often irreversible. There are several factors that are especially important in determining the enzyme’s shape, and these are closely regulated both in the living organism and in laboratory experiments to give optimum or most efficient enzyme activity: 1. SALT CONCENTRATION: If the salt concentration or ionic strength is very low or zero, the charged amino acid side chains of the enzyme with stick together. The enzyme will denature and form an inactive precipitate. If, on the other hand, the salt concentration is very high, enzyme will precipitate. An intermediate salt concentration such as that of blood (~0.9% or 150mM NaCl) or cytoplasm is optimum for most enzymes. 2.
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This note was uploaded on 10/22/2010 for the course CHEM 101-E taught by Professor Ji during the Spring '09 term at Drexel.

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Catalase Lab Activity-SA.rev - Anandan BIO122A Fall 2010...

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