Enzymes - Enzymes: A Quantitative Approach ENZYMES ARE...

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Enzymes: A Quantitative Approach ENZYMES ARE ESSENTIAL FOR LIFE Not all chemical reactions occur at the rapid rates we observe in lab settings. Many of these slow reactions, such as some metabolic processes, are essential for an organism to survive but, paradoxically, are not quick enough to sustain life. Biological catalystsare chemical agents that influence the rate of a reaction without changing the reaction. An enzyme is a catalytic protein that allows reactions to occur at much higher rates. With the help of enzymes, those slow reactions can occur quickly enough to sustain life. The amount of energy needed to begin the bond-breaking process in a reaction is known as the activation energy. Enzymes speed up reactions by lowering this energy barrier therefore allowing reactions to proceed much earlier than they would have with a higher energy barrier. ENZYME-SUBSTRATE COMPLEX Enzymes are substrate-specific. This means they are very “picky” and only react with specific substrates to form products. For example, this week in lab you will work with the enzyme, tyrosinase. Tyrosinase is found in many organisms, including humans. This lab will focus on the role tyrosinase plays in potatoes. (Note the suffix –ase in tyrosinase; this suffix nearly always denotes an enzyme.) Tyrosinase reacts with its substrate pyrocatechol to create the plant antibiotic hydroxyquinone. Hydroxyquinone is a yellowish-brown liquid that is found at the site of plant injury. Think of a bruise on your apple. The brown color is hydroxyquinone. In a normal enzymatic reaction the enzyme and substrate collide randomly in a solution and join at the enzyme’s active site. This collision works much like a lock and key effect. The active site has a specific shape that only a particular substrate fits into (with the exception of inhibitors which we will discuss later on). When the two are
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This note was uploaded on 04/04/2012 for the course BIO 124 taught by Professor Caralee during the Spring '08 term at New Mexico.

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Enzymes - Enzymes: A Quantitative Approach ENZYMES ARE...

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