Enzyme Catalysis - Enzyme Catalysis Introduction: Living...

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Enzyme Catalysis Introduction: Living cells produce globular proteins called enzymes to act as activators or accelerators for metabolic reactions. Enzymes make it possible for biochemical reactions to occur with a lower initial energy requirement. This way, cells can perform more activities at a relatively lower temperature and less energy expenditure. Enzymes are not changed after each reaction. They can perform their enzymatic functions repeatedly. The substrate is the substance on which enzymes act on to create products. Enzymes are substrate specific because of their functional shapes. Their folded conformation creates an area called active site. The different sequence of amino acids and their nature in the active site determines what substrates can bind with the enzyme. Even when other substrates are present, only those substrates with complementary shape can bind to the enzyme’s active site. Sometimes when substrates bind with an enzyme, the enzyme’s active site changes shape slightly. This change in active site is known as induced fit and it helps with catalysis of substrates to products. The rate of enzymatic activities can be affected by various factors like temperature, pH level, enzyme concentration, and substrate concentration. In general, an increase in temperature can increase enzymatic activities, but if the temperature is too high, enzymes will lose their weak bonds and start to change shape and lose their function. When an enzyme changes shape due to high temperature, it is known as enzyme denaturation. After an enzyme denatures, the substrates can no longer bind to the actives sites of the enzyme. As a result, reaction stops. The optimal pH level is enzyme specific because various enzymes work best at various pH ranges. Both the enzyme concentration and substrate concentration increase can cause an increase in the rate of enzymatic activities because the more concentrated enzymes or substrate are, the easier it is for substrates to bump into the active site of the enzymes. Therefore, the rate of reaction is increased. This lab is designed to examine the role of an enzyme in a biochemical reaction and determine the rate of the enzyme-catalyzed reaction under various conditions. In this case, a catalase is used to speed up the conversion of hydrogen peroxide (H 2 O 2 ) to water (H 2 O) and oxygen (O 2 ). Exercise 2A: Test of Catalase Activity
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This note was uploaded on 03/03/2010 for the course AP BIO AP BIO taught by Professor Apbioteacher during the Spring '09 term at École Normale Supérieure.

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Enzyme Catalysis - Enzyme Catalysis Introduction: Living...

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