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Questions and Answers

What is the role of enzymes in relation to activation energy?

  • Enzymes decrease the activation energy of reactions. (correct)
  • Enzymes increase the activation energy required for reactions.
  • Enzymes permanently alter the energy of reactants.
  • Enzymes have no effect on the activation energy.

    • Which statement accurately describes the transition state in a chemical reaction?

  • The transition state is equivalent to the substrate complex.
  • The transition state has the highest potential energy during the reaction. (correct)
  • The transition state does not affect the reaction rate.
  • The transition state is the lowest energy configuration.

    • Which of the following best defines the rate-limiting step in a chemical reaction?

  • The step with the lowest energy barrier.
  • The step with the highest activation energy. (correct)
  • The step that forms the most stable intermediate.
  • The step that consumes the most amount of reactants.

    • How do enzymes achieve a decrease in activation energy?

    <p>By stabilizing the transition state through various interactions.</p> Signup and view all the answers

    Which intermediate forms when a substrate binds to an enzyme?

    <p>Substrate-enzyme complex (ES).</p> Signup and view all the answers

    What effect do enzymes have on the reaction coordinate diagram?

    <p>They reduce the height of the activation energy barrier.</p> Signup and view all the answers

    What characteristic is associated with a flexible reactant in an uncatalyzed unimolecular reaction?

    <p>Higher activation energy than rigid reactants.</p> Signup and view all the answers

    What describes the molecular arrangement in the transition state?

    <p>It has a single fixed configuration.</p> Signup and view all the answers

    What type of reaction does an oxidoreductase enzyme primarily catalyze?

    <p>Transfer of electrons</p> Signup and view all the answers

    Which enzyme class is involved in the cleavage of bonds by elimination, resulting in double bonds or rings?

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

    Which type of reaction is catalyzed by hydrolases?

    <p>Hydrolysis reactions</p> Signup and view all the answers

    What defines the enzyme-substrate complex's function in enzymatic catalysis?

    <p>It facilitates the conversion of substrate into product.</p> Signup and view all the answers

    In the context of enzyme activity, which statement is true regarding the effect of enzymes on reaction free energy?

    <p>Enzymes have no effect on the free energy of the reaction.</p> Signup and view all the answers

    What is the primary role of isomerases in biochemical reactions?

    <p>They catalyze the formation of isomeric forms.</p> Signup and view all the answers

    Which of the following enzyme classes utilizes ATP or similar cofactors during condensation reactions?

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

    Which of the following is a characteristic of enzymes regarding substrate selectivity?

    <p>Binding can occur without any chemical reaction taking place.</p> Signup and view all the answers

    Which term refers to the pocket on an enzyme where substrate binding and catalysis occur?

    <p>Active site</p> Signup and view all the answers

    What is the main function of transferases in biochemical reactions?

    <p>To facilitate group transfer between molecules.</p> Signup and view all the answers

    What characterizes irreversible inhibitors in relation to enzyme activity?

    <p>They permanently deactivate the enzyme.</p> Signup and view all the answers

    Which of the following statements is true regarding competitive inhibition?

    <p>It interferes with the binding of the substrate to the enzyme's active site.</p> Signup and view all the answers

    How does uncompetitive inhibition affect the enzyme kinetics?

    <p>It does not change Vmax but decreases KM.</p> Signup and view all the answers

    Which statement correctly describes mixed inhibition?

    <p>It can bind to both the enzyme and the enzyme-substrate complex, affecting both binding and catalytic function.</p> Signup and view all the answers

    In a Lineweaver-Burk plot representing competitive inhibition, where do the lines intersect?

    <p>At the y-axis.</p> Signup and view all the answers

    What happens to KM in the presence of uncompetitive inhibitors?

    <p>KM decreases.</p> Signup and view all the answers

    Which type of inhibition can be characterized by a decrease in Vmax with no change in KM/Vmax ratio?

    <p>Uncompetitive Inhibition</p> Signup and view all the answers

    Which inhibitor can act as a suicide inhibitor?

    <p>Irreversible inhibitor</p> Signup and view all the answers

    Which type of catalysis involves a transient covalent bond between the enzyme and the substrate?

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

    What role do metal ions play in enzyme catalysis?

    <p>Stabilize negative charges</p> Signup and view all the answers

    Which amino acid groups are critical for covalent catalysis?

    <p>Amine, thiolate, and reactive serine</p> Signup and view all the answers

    What is the primary function of general acid-base catalysis in enzymes?

    <p>To donate and receive protons effectively</p> Signup and view all the answers

    In the context of enzymes, what is meant by 'acid-base catalysis'?

    <p>The transfer of protons between amino acids</p> Signup and view all the answers

    What distinguishes metal ion catalysis from other catalysis types?

    <p>Involvement of a metal ion bound to the enzyme</p> Signup and view all the answers

    Which of the following best describes the mechanism of chymotrypsin during digestion?

    <p>It breaks down proteins into small peptides using proteolytic activity</p> Signup and view all the answers

    Which statement about acid-base catalysis is correct?

    <p>It optimizes proton transfer within the enzyme's active site</p> Signup and view all the answers

    What does a nucleophile in the context of covalent catalysis typically refer to?

    <p>A reactive component such as serine or thiolate on the enzyme</p> Signup and view all the answers

    Which of the following best describes the role of protons in general acid-base catalysis?

    <p>They are optimized for effective transfer in the enzyme's active site</p> Signup and view all the answers

    Under which condition does the Michaelis-Menten equation simplify to V0 = Vmax?

    <p>[S] is significantly greater than Km</p> Signup and view all the answers

    What is a key characteristic of the Lineweaver-Burk plot?

    <p>It provides a linear representation of Michaelis-Menten data.</p> Signup and view all the answers

    What does the specificity constant kcat/Km measure?

    <p>The efficiency of the enzyme-substrate interaction</p> Signup and view all the answers

    Which of the following enzymes shows a kcat/Km ratio close to the diffusion-controlled limit?

    <p>Acetylcholinesterase with Acetylcholine</p> Signup and view all the answers

    What happens to the Km term when substrate concentration [S] is very high?

    <p>It becomes insignificant in the denominator.</p> Signup and view all the answers

    In which scenario does reaction velocity not depend on substrate concentration?

    <p>When [S] is incredibly high.</p> Signup and view all the answers

    Which statement is true regarding kcat and Km for different enzymes?

    <p>Different enzymes can have different Km and kcat values.</p> Signup and view all the answers

    What does a nonlinear Michaelis-Menten plot primarily help to determine?

    <p>The kinetic parameters Km and Vmax</p> Signup and view all the answers

    Which of the following equations represents first order kinetics?

    <p>V0 = Vmax[S]/Km</p> Signup and view all the answers

    What is the typical kcat/Km range for enzymes that are diffusion-controlled?

    <p>Between 10^8 and 10^9 M–1s–1</p> Signup and view all the answers

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