Enzyme Kinetics and Inhibition Quiz
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Questions and Answers

What are enzymes?

  • Substances that increase the rate of reaction
  • Catalysts involved in biochemical reactions (correct)
  • Molecules that act as the reactant in a biochemical reaction
  • Proteins that bind to the active site
  • Where is the active site located?

  • Inside the enzyme's core
  • Within the substrate molecule
  • In the cytoplasm of the cell
  • On the surface of the enzyme (correct)
  • What is the function of the active site?

  • Area for enzyme regulation
  • Location where the enzyme binds to the substrate and catalysis occurs (correct)
  • Storage site for excess substrates
  • Site for product formation
  • What is a substrate?

    <p>A molecule that acts as the reactant in an enzymatically catalyzed reaction</p> Signup and view all the answers

    How are enzymes usually structured?

    <p>Globular proteins</p> Signup and view all the answers

    What can be deduced about the mechanism of an enzyme?

    <p>From structural, kinetic, and spectral data</p> Signup and view all the answers

    What is the role of enzymes in biochemical reactions?

    <p>To increase the rate of reaction</p> Signup and view all the answers

    What is the active site often formed by?

    <p>Residues on turns or coils</p> Signup and view all the answers

    What fraction of biochemical reactions use multiple substrates?

    <p>More than 60%</p> Signup and view all the answers

    What do enzymes bind to at the active site?

    <p>The substrate</p> Signup and view all the answers

    What is the primary role of a substrate in an enzymatically catalyzed reaction?

    <p>To act as the reactant</p> Signup and view all the answers

    What is the typical structure of the active site?

    <p>Cleft, pocket, or trench</p> Signup and view all the answers

    What is the main function of enzymes in relation to reaction rates?

    <p>Decreasing activation energy</p> Signup and view all the answers

    Which enzyme classification includes enzymes that catalyze the transfer of functional groups?

    <p>Transferases</p> Signup and view all the answers

    What does the Michaelis constant (KM) represent in the Michaelis-Menten equation?

    <p>Substrate concentration</p> Signup and view all the answers

    What does the Lineweaver-Burke plot provide a graphical representation of?

    <p>Vmax and KM</p> Signup and view all the answers

    What does the turnover number (kcat) measure?

    <p>Catalytic efficiency</p> Signup and view all the answers

    At what point does the diffusion-controlled limit occur?

    <p>When the rate-limiting step is the diffusion of enzyme and substrate</p> Signup and view all the answers

    What characterizes irreversible inhibitors?

    <p>They prevent the generation of products</p> Signup and view all the answers

    In competitive inhibition, what do inhibitors compete directly with?

    <p>Substrate</p> Signup and view all the answers

    What is the impact of uncompetitive inhibition on Vmax and KM?

    <p>Decreases Vmax, increases KM</p> Signup and view all the answers

    What characterizes suicide inhibitors?

    <p>They irreversibly block enzyme function by covalently modifying the active site</p> Signup and view all the answers

    What is the defining feature of mixed inhibition?

    <p>It is effective regardless of substrate concentration</p> Signup and view all the answers

    Which enzyme classification includes enzymes that catalyze the breaking of chemical bonds through elimination reactions?

    <p>Lyases</p> Signup and view all the answers

    Which type of catalysis involves amino acid side chains donating or accepting protons?

    <p>General acid–base catalysis</p> Signup and view all the answers

    What type of catalysis involves active site metal acting as a redox active center?

    <p>Metal ion catalysis</p> Signup and view all the answers

    Which catalysis involves nucleophilic or electrophilic attack on an atom resulting in a covalent intermediate?

    <p>Covalent catalysis</p> Signup and view all the answers

    What type of catalysis is sometimes referred to as electrostatic catalysis?

    <p>Electrostatic catalysis</p> Signup and view all the answers

    Which type of catalysis involves weak forces lowering entropy?

    <p>General acid–base catalysis</p> Signup and view all the answers

    In induced fit, enzymes bind substrates that favor which state?

    <p>Transition state</p> Signup and view all the answers

    Which enzyme catalyzes the breaking of chemical bonds through elimination reactions?

    <p>Lipase</p> Signup and view all the answers

    What is the primary function of lysozyme?

    <p>Immune defense</p> Signup and view all the answers

    Which amino acids are involved in covalent catalysis?

    <p>Serine, Aspartate, Cysteine</p> Signup and view all the answers

    What is the role of metal ions in metal ion catalysis?

    <p>Acting as cofactors</p> Signup and view all the answers

    What is the impact of induced fit on the entropy of the system?

    <p>Decreases entropy</p> Signup and view all the answers

    What is the mechanism of action of lysozyme?

    <p>Cleaving glycosidic bonds</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of carbon dioxide to carbonic acid using Zn2+ in the active site?

    <p>Carbonic anhydrase</p> Signup and view all the answers

    Which class of proteases does chymotrypsin belong to?

    <p>Serine proteases</p> Signup and view all the answers

    Which technique is used to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone?

    <p>Affinity labeling</p> Signup and view all the answers

    Which enzyme regulation method involves altering gene expression, sequestration in compartments, limiting substrate access, and covalent modification?

    <p>Enzyme regulation</p> Signup and view all the answers

    What is the inactive form of chymotrypsin?

    <p>Chymotrypsinogen</p> Signup and view all the answers

    Which process involves protein kinases adding phosphate groups and phosphatases removing them?

    <p>Phosphorylation</p> Signup and view all the answers

    What type of regulation can increase or decrease enzymatic activity by binding at a site other than the active site?

    <p>Allosteric regulation</p> Signup and view all the answers

    Which enzyme is an example of regulation via phosphorylation?

    <p>Src</p> Signup and view all the answers

    What is the technique to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone?

    <p>Affinity labeling</p> Signup and view all the answers

    What is the enzyme that degrades proteins and includes trypsin, chymotrypsin, and elastase?

    <p>Proteases</p> Signup and view all the answers

    Study Notes

    Enzyme Kinetics and Inhibition

    • Enzyme classifications include oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
    • Enzymes lower activation energy (Ea) to increase reaction rate without changing thermodynamic parameters.
    • The Michaelis-Menten equation relates substrate concentration to Vmax and KM, with Vmax representing maximal velocity and KM the Michaelis constant.
    • Saturation kinetic curve shows enzyme saturation with substrate and the impact of high or low KM values.
    • Lineweaver-Burke plot provides a double reciprocal of the Michaelis-Menten equation, offering an easier method for interpreting graphical data.
    • Turnover number (kcat) measures the number of reactions an enzyme can catalyze per unit of time, indicating catalytic efficiency.
    • Diffusion controlled limit occurs when the rate-limiting step becomes the diffusion of enzyme and substrate, with a rate between 108 and 109 M−1 sec−1.
    • Inhibitors can be irreversible or reversible, preventing the generation of products.
    • Suicide inhibitors irreversibly block enzyme function by covalently modifying the active site, examples include pesticides and nerve agents.
    • Competitive inhibition involves molecules similar to the substrate shape, competing directly with the substrate and can be overcome with high substrate concentration.
    • Uncompetitive inhibition binds to the ES complex, decreasing both Vmax and KM.
    • Mixed inhibition combines features of competitive and uncompetitive inhibitors, being effective regardless of substrate concentration.

    Enzyme Catalysis and Regulation

    • Carbonic anhydrase is found in erythrocytes and catalyzes the conversion of carbon dioxide to carbonic acid using Zn2+ in the active site.
    • Proteases are enzymes that degrade proteins and include trypsin, chymotrypsin, and elastase, and are important in protein maturation, blood clotting, and protein trafficking.
    • Different classes of proteases, including serine, aspartyl, metallo-, and cysteine proteases, employ similar chemistry with conserved topology and overall structure.
    • Chymotrypsin is a serine protease that cleaves dietary protein and contains a catalytic triad with Aspartate, Histidine, and Serine.
    • Affinity labeling is a technique to specifically label active site residues with examples like Diisopropylfluorophosphate and Tosyl-L-phenylalanine chloromethyl ketone.
    • Enzyme regulation can be achieved through altering gene expression, sequestration in compartments, limiting substrate access, and covalent modification and allosteric regulation methods.
    • Covalent modification involves the covalent addition or removal of groups from proteins, with proteolytic cleavage and phosphorylation as common means of activation.
    • Zymogens are inactive enzyme precursors that require proteolytic activation, with chymotrypsinogen being the inactive form of chymotrypsin.
    • Phosphorylation is another example of protein activation facilitated by protein kinases adding phosphate groups and phosphatases removing them, regulated through signaling cascades.
    • Src is an example of regulation via phosphorylation.
    • Allosteric regulation can increase or decrease enzymatic activity by binding at a site other than the active site, with relaxed (R) and tense (T) states and sigmoidal activity curves.
    • Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein. Copyright © 2019 John Wiley & Sons, Inc.

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    Description

    Test your knowledge of enzyme kinetics and inhibition with this quiz. Explore topics such as Michaelis-Menten equation, turnover number, saturation kinetic curve, Lineweaver-Burke plot, and various types of enzyme inhibitors including competitive, uncompetitive, and mixed inhibition.

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