Biochem 7: Enzyme Kinetics
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Questions and Answers

Which type of enzyme inhibition occurs when the inhibitor binds to the enzyme-substrate complex?

  • Noncompetitive inhibition
  • Competitive inhibition
  • Irreversible inhibition
  • Uncompetitive inhibition (correct)

    • In uncompetitive inhibition, is the Vmax lower or higher in the presence of the inhibitor?

  • Higher
  • Lower (correct)

    • Does the affinity of the enzyme appear to go up or down in the presence of the uncompetitive inhibitor?

  • Go down
  • Go up (correct)

    • Which type of enzyme inhibition occurs when the inhibitor can bind to both the enzyme and the enzyme-substrate complex?

    <p>Competitive inhibition</p> Signup and view all the answers

    In competitive inhibition, is the Vmax lower or higher in the presence of the inhibitor?

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

    Does the affinity of the enzyme appear to go up or down in the presence of the competitive inhibitor?

    <p>Go down</p> Signup and view all the answers

    Which type of enzyme inhibition occurs when the inhibitor can bind to both the enzyme and the enzyme-substrate complex, but at different binding sites?

    <p>Noncompetitive inhibition</p> Signup and view all the answers

    In noncompetitive inhibition, is the Vmax lower or higher in the presence of the inhibitor?

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

    Does the affinity of the enzyme appear to go up or down in the presence of the noncompetitive inhibitor?

    <p>Go down</p> Signup and view all the answers

    Which type of enzyme inhibition occurs when the inhibitor forms a covalent bond with the active site of the enzyme?

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

    Which of the following is true about Michaelis-Menten kinetics?

    <p>It applies to both first order and zero order reactions</p> Signup and view all the answers

    What is the role of glucokinase in the liver?

    <p>It catalyzes the conversion of glucose to glucose-6-phosphate</p> Signup and view all the answers

    What is the difference between glucokinase and hexokinase in terms of Vmax?

    <p>Glucokinase has a higher Km than hexokinase</p> Signup and view all the answers

    What is the difference between glucokinase and hexokinase in terms of Km?

    <p>Glucokinase has a lower Km than hexokinase</p> Signup and view all the answers

    What is the purpose of a Lineweaver-Burk plot?

    <p>To determine the Km and Vmax of an enzyme</p> Signup and view all the answers

    Which of the following is an example of reversible enzyme inhibition?

    <p>Competitive inhibition</p> Signup and view all the answers

    What is the graph of an allosteric enzyme in the presence of an inhibitor?

    <p>A sigmoidal curve</p> Signup and view all the answers

    What is the ratio that determines enzyme efficiency?

    <p>Kcat/Km</p> Signup and view all the answers

    Which of the following is true about first order reactions?

    <p>Their reaction rate depends on the concentration of reactants</p> Signup and view all the answers

    Which of the following is true about zero order reactions?

    <p>They have a constant reaction rate</p> Signup and view all the answers

    Which enzyme is active even during fasting?

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

    What enzyme doesn't become active until after a high-carbohydrate meal?

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

    What is the main role of glucokinase and hexokinase?

    <p>Both glycolysis and glycogenesis</p> Signup and view all the answers

    What does a higher Km tell you about the affinity of glucokinase for glucose, compared to the affinity of hexokinase for glucose?

    <p>Hexokinase has higher affinity</p> Signup and view all the answers

    What pathway does hexokinase feed into if it can't do glycogenesis?

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

    Why is hexokinase inhibited by glucose-6-P, but glucokinase is not?

    <p>Hexokinase is allosterically inhibited by glucose-6-P</p> Signup and view all the answers

    What is the general purpose of very efficient enzymes?

    <p>To convert substrates into products rapidly</p> Signup and view all the answers

    Which is a more efficient enzyme: one with a larger or smaller value for Kcat/Km?

    <p>Larger value for Kcat/Km</p> Signup and view all the answers

    What are some applications of enzyme inhibition?

    <p>Preventing the spread of cancer cells</p> Signup and view all the answers

    What type of reversible inhibition is exemplified by methotrexate?

    <p>Competitive inhibition</p> Signup and view all the answers

    Which of the following is an example of enzyme regulation via reversible covalent modification?

    <p>Phosphorylation of glycogen synthase inhibits glycogenesis</p> Signup and view all the answers

    Which of the following is FALSE regarding enzymes?

    <p>The enzyme is used up by the reaction and will need to be remade via transcription and translation</p> Signup and view all the answers

    Which of the following is an example of enzyme regulation via irreversible covalent modification?

    <p>Cleavage of a peptide bond in a proenzyme to form an active enzyme</p> Signup and view all the answers

    What kind of bonds form the primary structure of a protein?

    <p>Peptide bond</p> Signup and view all the answers

    When a heavy metal such as lead (Pb+2) interacts with bonds within a protein, it can denature the protein. Which of the following bonds are vulnerable to this type of denaturation?

    <p>Disulfide bridge</p> Signup and view all the answers

    What important piece of information can be gained from Michaelis Menten kinetics?

    <p>The affinity of an enzyme for its coenzyme</p> Signup and view all the answers

    Which of the following characteristics indicates the highest enzyme efficiency?

    <p>High Kcat, Low Km</p> Signup and view all the answers

    Which of the following is true of any pseudo-first order reaction?

    <p>One substrate has a concentration is excess of what is needed</p> Signup and view all the answers

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