Enzyme Kinetics
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Enzyme Kinetics

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Questions and Answers

What role do enzymes play in chemical reactions according to Transition State Theory?

  • They convert substrates into products directly.
  • They stabilize the transition state. (correct)
  • They add extra energy to the reactants.
  • They slow down the reaction rates.

    • Which of the following best describes the function of lysozyme?

  • It breaks down peptidoglycan in bacterial cell walls. (correct)
  • It serves as a substrate for protein synthesis.
  • It binds to iron to support oxygen transport.
  • It enhances the growth of bacterial cells.

    • What are the two primary factors that influence enzyme kinetics according to the content provided?

  • pH and substrate concentration. (correct)
  • Temperature and color change.
  • Pressure and volume of reactants.
  • Light exposure and enzyme concentration.

    • In the context of enzyme action, what is the significance of substrate binding?

    <p>It positions substrates correctly for reaction.</p> Signup and view all the answers

    What is the importance of the Induced Fit Model in enzymatic reactions?

    <p>It highlights that enzymes change shape to enhance binding.</p> Signup and view all the answers

    Which statement is true regarding the transition state in reactions catalyzed by enzymes?

    <p>Transition state stability is essential for lowering activation energy.</p> Signup and view all the answers

    Which mechanism does an enzyme use to promote the formation of the transition state?

    <p>By binding the substrate in the correct orientation.</p> Signup and view all the answers

    What is a significant feature of enzymes compared to other catalysts?

    <p>Enzymes reduce the activation energy of reactions significantly.</p> Signup and view all the answers

    What is a primary function of lysozyme in the human body?

    <p>Inhibits the growth of bacteria</p> Signup and view all the answers

    Which model describes how an enzyme binds to a substrate by distorting it into a transition state?

    <p>Induced Fit Model</p> Signup and view all the answers

    What does Km represent in enzyme kinetics?

    <p>The substrate concentration at half Vmax</p> Signup and view all the answers

    Which factors affect enzyme reaction rates according to enzyme kinetics?

    <p>Temperature, pH, and substrate concentration</p> Signup and view all the answers

    In the context of the Induced Fit Model, what happens when glucose binds to hexokinase?

    <p>Two protein domains close together</p> Signup and view all the answers

    What is Vmax in enzyme kinetics?

    <p>The maximum rate of reaction at saturation</p> Signup and view all the answers

    Which statement accurately reflects the role of the active site of an enzyme?

    <p>It binds substrates and may play a role in catalysis</p> Signup and view all the answers

    Which of the following best describes Transition State Theory?

    <p>The enzyme lowers the activation energy of the transition state</p> Signup and view all the answers

    Which of these factors would NOT typically affect enzyme kinetics?

    <p>Color of the substrate</p> Signup and view all the answers

    How does substrate concentration influence enzyme kinetics?

    <p>It can lead to saturation, influencing Vmax</p> Signup and view all the answers

    What is the definition of one International Unit (U) of an enzyme?

    <p>The quantity of enzyme that catalyzes the conversion of 1μmol of substrate to product per minute</p> Signup and view all the answers

    In non-competitive enzyme inhibition, which of the following statements is true?

    <p>Km remains unchanged and Vmax decreases</p> Signup and view all the answers

    What characterizes allosteric regulation in enzymes?

    <p>Usually involves multi-subunit proteins with multiple active sites</p> Signup and view all the answers

    Which factor does NOT affect enzyme kinetics?

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

    What mechanism describes the binding of a substrate to an enzyme where the enzyme changes shape to fit the substrate?

    <p>Induced fit model</p> Signup and view all the answers

    How does a competitive inhibitor affect enzyme activity?

    <p>By binding reversibly to the active site, increasing Km</p> Signup and view all the answers

    Which of the following statements accurately describes transition state theory?

    <p>Transition state is a high-energy state that precedes product formation</p> Signup and view all the answers

    What describes the effect of cimetidine on the metabolism of steroids?

    <p>It reduces the metabolism by competing for the active site</p> Signup and view all the answers

    Which statement accurately describes enzyme kinetics?

    <p>The reaction velocity approaches Vmax with excess substrate</p> Signup and view all the answers

    What is the primary role of lysozyme?

    <p>To hydrolyze bacterial cell wall components</p> Signup and view all the answers

    Study Notes

    Lysozyme

    • Found in tears, saliva, human milk and mucus
    • Part of the body’s innate immune system

    Transition State Theory

    • Enzymes reduce the activation energy of a reaction by binding to the transition structure and stabilising it

    Induced Fit Model

    • The enzyme and substrate fit together perfectly
    • Upon binding, the substrate can induce a conformational change in the enzyme which may enhance catalytic function
    • Active site: pocket of amino-acids that bind substrate or play a role in catalysis
    • Example: Hexokinase; Binding of glucose causes two protein domains to close together, effectively closing the binding cleft

    Enzyme Kinetics

    • Rate of reaction is affected by temperature, pH and substrate concentration
    • Rate of reaction is reflected by the slope of a graph, the enzyme capacity is the hight of the curve
    • Vmax is the maximum rate of reaction and is dependent on enzyme concentration
    • Km refers to the substrate concentration at which the enzyme converts substrates into products at half its maximal velocity
    • Km reflects the affinity of the substrate for the enzyme
    • Enzymes are the most efficient catalysts known

    Practical Units of Enzyme Measurement

    • Activity of an enzyme = ‘specific activity’ = μmol / min / mg - Micromoles of substrate converted to product per minute per milligram of enzyme protein
    • International Unit (U) / ml - 1U = the quantity of enzyme which catalyses the conversion of 1μmol of substrate to product per minute under a defined set of optimal conditions
    • katal (kat) - Amount of enzyme that converts one mole of substrate to product per second

    Enzyme Inhibition

    • Competitive Inhibition:*
    • Inhibitor binds reversibly to the active site
    • Km increases
    • Vmax remains unchanged
    • Non-competitive Inhibition:*
    • Inhibitor binds outside of the active site, decreasing the reaction rate
    • Km remains unchanged
    • Vmax decreases

    Allosteric Regulation

    • Usually multi-subunit proteins with multiple active sites
    • Involves the binding of regulatory molecules at sites other than the active site which then mediate conformational changes in the enzyme
    • These changes may either enhance or inhibit catalytic activity

    Clinical Relevance

    • Drugs may compete for the active site of a single cytochrome P450 enzyme
    • This can lead to variable effects on drug metabolism, especially for patients receiving multiple drugs
    • Cimetidine (inhibits stomach acid production):
      • Binds competitively to several cytochrome P450 enzymes
      • Reduces the metabolism of endogenous and administered steroids

    Transition State Theory

    • Lysozyme breaks down peptidoglycan in bacterial cell walls

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    Related Documents

    Enzyme Kinetics Lecture Notes PDF

    Description

    Explore the fascinating world of enzymes, their mechanisms, and the factors influencing their activity. This quiz covers topics such as lysozyme, transition state theory, and the induced fit model. Test your understanding of enzyme kinetics and the dynamics of biochemical reactions.

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