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Enzymes:
The Biological Catalysts
Energy of Activation• Most reactions do not start spontaneously• They require energy, such as a spark, to get started. • This is called activation energy
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Energy of Activation
• The energy used to break the bonds in the reactants so they can be reformed in the products is called the energy of activation.
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Enzymes
• Enzymes are biological catalysts that increase the reaction rate of biochemical reactions.
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Characteristics of enzymes
A. Made of proteins (or RNA).
B.They are very specific and only work with a certain set of reactants or substrates that fit on their active site.
The enzyme shown is lysozyme
Induced Fit
C. Enzymes can be used over and over again.
D. When an enzyme binds with the substrate, the bonded substrate interacts with the enzyme causing it to change shape. This change in shape facilitates the chemical reaction to occur. This is called the induced fit.
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Enzyme Example Ribonuclease
• Ribonuclease decomposes RNA, and the nucleotides can be recycled.
• The purple part is the enzyme; the green part is the substrate (RNA).
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Enzymes Work by Lowering the Energy of Activation
E. Enzymes increase the reaction rate by lowering the energy of activation.
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The Enzyme Sucrase Decomposing Sucrose
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Initial Velocity• The reaction rate of an enzymatic reaction is always
fastest at the beginning because plenty of substrate is available.
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Effects on Reaction Rates
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Temperature increases enzyme action until the enzyme protein is denatured
Effect on Reaction Rates
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Most enzymes work best with a pH of 7, but some can work in other ranges before denaturing
Effect onReaction Rates
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Competitive Inhibitors block enzyme activity by mimicking the substrate
Effect of Noncompetitive Inhibitors and Enzymatic Reaction Rates
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Noncompetitve inhibitors block enzyme function too, but attach a different point than the active site
Draw and Label Activation Energy Diagram
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Reactions to Know
• Hydrolysis Rxn – breaks apart a compound by adding a water molecule
• Dehydration Synthesis Rxn – links two compouunds by creating and releasing a water molecule
• Endergonic Rxn – a reaction that requires energy
• Exergonic Rxn – a reaction that releases energy
• Redox Rxn – a reaction that involves transferring electrons
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