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 (B)</p> Signup and view all the answers

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

<p>Lower (A)</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 (A)</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 (B)</p> Signup and view all the answers

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

<p>Lower (A)</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 (B)</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 (D)</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 (B)</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 (B)</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 (A)</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 (B)</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 (B)</p> Signup and view all the answers

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

<p>Competitive inhibition (A)</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 (D)</p> Signup and view all the answers

What is the ratio that determines enzyme efficiency?

<p>Kcat/Km (B)</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 (D)</p> Signup and view all the answers

Which of the following is true about zero order reactions?

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

Which enzyme is active even during fasting?

<p>Hexokinase (B)</p> Signup and view all the answers

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

<p>Glucokinase (C)</p> Signup and view all the answers

What is the main role of glucokinase and hexokinase?

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

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

<p>Glycolysis (B)</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 (A)</p> Signup and view all the answers

What is the general purpose of very efficient enzymes?

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

What are some applications of enzyme inhibition?

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

What type of reversible inhibition is exemplified by methotrexate?

<p>Competitive inhibition (C)</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 (C)</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 (D)</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 (B)</p> Signup and view all the answers

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

<p>Peptide bond (B)</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 (D)</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 (A)</p> Signup and view all the answers

Which of the following characteristics indicates the highest enzyme efficiency?

<p>High Kcat, Low Km (B)</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 (C)</p> Signup and view all the answers

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