Unit 4 Target 1: Enzymes Quiz

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Unit 4 Target 1: Enzymes Quiz - Quiz


Questions and Answers
  • 1. 

    How do enzymes speed up chemical reactions?  

    • A.

      By reducing activation energy

    • B.

      By reducing energy produced by the reaction

    • C.

      By increasing activation energy

    • D.

      By increasing energy produced by the reaction

    Correct Answer
    A. By reducing activation energy
    Explanation
    Enzymes speed up chemical reactions by reducing activation energy. Activation energy is the energy required to start a chemical reaction. Enzymes lower this energy barrier, making it easier for the reaction to occur. They do this by binding to the reactant molecules and bringing them closer together, allowing them to interact more easily and increasing the likelihood of a successful reaction. By reducing the activation energy, enzymes increase the rate of the reaction without being consumed or permanently altered in the process.

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  • 2. 

    Pepsin is a protein-digesting enyme in the human stomach. Antacids cause the pH of the stomach to increase and protein digestion becomes less efficient. What occurs to reduce the efficiency of protein digestion?

    • A.

      Antacids break the covalent bonds within pepsin.

    • B.

      Pepsin dissolves antacids in the gastric juice.

    • C.

      The active site of pepsin changes shape.

    • D.

      The concentration of pepsin increases.

    Correct Answer
    C. The active site of pepsin changes shape.
    Explanation
    Antacids work by increasing the pH of the stomach, making it more alkaline. This change in pH can affect the structure and function of pepsin, which is an enzyme that works best in an acidic environment. The active site of an enzyme is the region where the substrate binds and the chemical reaction takes place. When the pH increases, the active site of pepsin undergoes a conformational change, altering its shape. This change in shape can prevent pepsin from effectively binding to and digesting proteins, reducing the efficiency of protein digestion.

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  • 3. 

    Two students conduct an experiment in which they measure the concentration of an enzyme in a test tube at 1 minute intervals over the course of an enzymatic reaction. Each of the students makes a prediction about what will happen to the enzyme concentration as the reaction progresses.Student 1 predicts that the concentration of the enzyme in the test tube will decrease as the reaction progresses.Student 2 predicts that the concentration of the enzyme in the test tube will stay the same as the reaction progresses.The results of the experiment will most likely support the prediction of which student? 

    • A.

      Student 1; enzymes are depleted as a reaction progresses.

    • B.

      Student 1; enzymes are not depleted as a reaction progresses.

    • C.

      Student 2; enzymes are depleted as a reaction progresses.

    • D.

      Student 2; enzymes are not depleted as a reaction progresses.

    Correct Answer
    D. Student 2; enzymes are not depleted as a reaction progresses.
    Explanation
    The correct answer is Student 2; enzymes are not depleted as a reaction progresses. Enzymes are catalysts that facilitate chemical reactions without being consumed in the process. Therefore, the concentration of the enzyme in the test tube will remain the same as the reaction progresses.

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  • 4. 

    Without enzymes, the chemical reactions in the body would   

    • A.

      Happen too fast.

    • B.

      Occur at much the same rate as they do with enzymes.

    • C.

      Require a different pH.

    • D.

      Occur too slowly to support life processes.

    Correct Answer
    D. Occur too slowly to support life processes.
    Explanation
    Enzymes are essential for speeding up chemical reactions in the body. Without enzymes, these reactions would occur at a significantly slower rate, which would not be sufficient to support the necessary life processes. Therefore, the correct answer is that without enzymes, the chemical reactions in the body would occur too slowly to support life processes.

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  • 5. 

    Which of the following statements about enzymes is NOT true?      

    • A.

      Enzymes work best at a specified pH.

    • B.

      All enzymes have the same shape as their substrates.

    • C.

      Enzymes are proteins.

    • D.

      The shape of an enzyme allows it to do its job.

    Correct Answer
    B. All enzymes have the same shape as their substrates.
    Explanation
    Enzymes work best at a specified pH, which means that they function optimally within a specific pH range. Enzymes are indeed proteins, as they are composed of amino acids. The shape of an enzyme is crucial for its function, as it allows the enzyme to bind with its specific substrate and catalyze a chemical reaction. However, enzymes do not have the same shape as their substrates. Instead, enzymes have a unique three-dimensional structure that complements the shape of their substrates, allowing for a specific and efficient interaction.

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  • 6. 

    Which of the following statements is true about catalysts?

    • A.

      Catalysts slow down the rate of chemical reactions.

    • B.

      All catalysts are enzymes.

    • C.

      Catalysts are used up during a chemical reaction.

    • D.

      Catalysts lower the activation energy of a chemical reaction.

    Correct Answer
    D. Catalysts lower the activation energy of a chemical reaction.
    Explanation
    Catalysts are substances that speed up the rate of a chemical reaction by lowering the activation energy required for the reaction to occur. They do not slow down the rate of chemical reactions. While some catalysts may be enzymes, not all catalysts are enzymes. Catalysts are not used up during a chemical reaction, as they are not consumed in the reaction and can be used repeatedly. Therefore, the correct statement is that catalysts lower the activation energy of a chemical reaction.

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  • 7. 

    Enzymes affect the reactions in living cells by changing the 

    • A.

      Products of the reaction.

    • B.

      Speed of the reaction.

    • C.

      Temperature of the reaction.

    • D.

      PH of the reaction.

    Correct Answer
    B. Speed of the reaction.
    Explanation
    Enzymes are catalysts that speed up chemical reactions in living cells. They do so by lowering the activation energy required for the reaction to occur. This means that enzymes increase the rate or speed at which the reaction takes place. Enzymes themselves are not consumed or changed during the reaction, and they do not affect the products or the final outcome of the reaction. Therefore, the correct answer is that enzymes affect the speed of the reaction.

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  • 8. 

    The active site of an enzyme is

    • A.

      Where the reactant fits into the enzyme

    • B.

      Where the enzymes and molecule bond together

    • C.

      When the balance of living organisms affects the enzyme

    • D.

      The same shape in all enzymes

    Correct Answer
    A. Where the reactant fits into the enzyme
    Explanation
    The active site of an enzyme is where the reactant fits into the enzyme. This site is specifically shaped to accommodate the reactant molecule, allowing for a precise and specific interaction between the enzyme and the substrate. The active site provides a favorable environment for the reaction to occur, facilitating the formation of the enzyme-substrate complex and the subsequent conversion of the substrate into product. The specificity and complementary shape of the active site ensure that only the correct reactant molecule can bind and undergo the enzymatic reaction.

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  • 9. 

    What is the term used to describe the energy needed to get a reaction started?

    • A.

      Adhesion energy

    • B.

      Activation energy

    • C.

      Cohesion energy

    • D.

      Chemical energy

    Correct Answer
    B. Activation energy
    Explanation
    Activation energy is the term used to describe the energy needed to get a reaction started. It is the minimum amount of energy required for a chemical reaction to occur. This energy is needed to break the bonds of the reactant molecules and initiate the formation of new bonds in the product molecules. Activation energy acts as a barrier that must be overcome for a reaction to proceed. Once the activation energy is surpassed, the reaction can continue on its own without any additional energy input.

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  • 10. 

    A substance that accelerates the rate of a chemical reaction is called a(an) 

    • A.

      Catalyst.

    • B.

      Lipid.

    • C.

      Molecule.

    • D.

      Element.

    Correct Answer
    A. Catalyst.
    Explanation
    A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by providing an alternative pathway with lower activation energy, allowing the reaction to occur more quickly. This is different from other options such as lipid, molecule, or element, which do not have the specific property of accelerating chemical reactions.

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  • 11. 

    Refer to the graph above. Reaction 3 in the graph

    • A.

      Probably occurred in the presence of a catalyst.

    • B.

      Requires a greater activation energy than reaction 2.

    • C.

      Is the same as reaction 1, but faster.

    • D.

      Takes longer than reaction 2.

    Correct Answer
    A. Probably occurred in the presence of a catalyst.
    Explanation
    The graph shows the energy profile of three reactions. Reaction 3 is indicated by the highest peak, suggesting that it requires a higher activation energy compared to reaction 2. However, it is not the same as reaction 1 because it occurs at a higher energy level. The fact that reaction 3 has a higher activation energy suggests that it may have occurred in the presence of a catalyst, which lowers the activation energy and speeds up the reaction.

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  • Current Version
  • Mar 16, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Sep 24, 2014
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    Jdowdyrobinson
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