Biology Chapter 6: Enzymes Flashcards
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Questions and Answers

In general, enzymes are what kinds of molecules?

  • Minerals
  • Lipids
  • Nucleic acids
  • Proteins (correct)
  • Carbohydrates
  • Enzymes work by _____

  • Decreasing the potential energy difference between reactant and product
  • Adding energy to a reaction
  • Increasing the potential energy difference between reactant and product
  • Reducing energy of activation (correct)
  • Adding a phosphate group to a reactant
  • An enzyme _____

  • Can bind to nearly any molecule
  • Is an organic catalyst (correct)
  • Is a source of energy for endergonic reactions
  • Increases the energy of activation of a reaction
  • Is an inorganic catalyst
  • What name is given to the reactants in an enzymatically catalyzed reaction?

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

    As a result of its involvement in a reaction, an enzyme _____

    <p>Is unchanged</p> Signup and view all the answers

    In a graph of energy vs reactants and products, what part of the parabola is the energy of activation found?

    <p>It is found between the reactant and the top or cusp of the curve.</p> Signup and view all the answers

    What must be overcome in order for a reaction to proceed?

    <p>The energy of activation must be overcome.</p> Signup and view all the answers

    Define an exergonic reaction.

    <p>A spontaneous chemical reaction, in which there is a net release of free energy.</p> Signup and view all the answers

    If exergonic reactions occur spontaneously, what keeps molecules from breaking apart and cell chemistry from racing out of control?

    <p>Some energy must be added to get the reaction going; this is known as the energy of activation.</p> Signup and view all the answers

    How does a living cell overcome the energy barrier for its metabolic reactions?

    <p>A special kind of protein called an enzyme is the answer.</p> Signup and view all the answers

    An enzyme serves as a ___________, ___________ without __________.

    <p>Biological catalyst, increasing the rate of a reaction without being changed into a different molecule.</p> Signup and view all the answers

    Is an enzyme selective or nonselective?

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

    Why is an enzyme so specific?

    <p>Its three-dimensional shape allows it to act only on specific molecules.</p> Signup and view all the answers

    What is the substrate?

    <p>The reactant on which an enzyme works.</p> Signup and view all the answers

    What is the active site?

    <p>The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.</p> Signup and view all the answers

    In a graph of enzymatic activity, what is the most reasonable explanation for low activity at 0 degrees Celsius?

    <p>There is too little activation energy available from the environment.</p> Signup and view all the answers

    How many active sites are generally found in an enzyme?

    <p>One active site at which catalysis can occur.</p> Signup and view all the answers

    What happens to enzymes as the substrate concentration increases?

    <p>The reaction rate increases until the active site is saturated with substrate.</p> Signup and view all the answers

    What happens to the rate of a reaction involving an enzyme when saturation is reached?

    <p>The rate of the reaction will not increase with the concentration of substrates.</p> Signup and view all the answers

    In a graph of reaction rate vs substrate concentration, at what point does the reaction rate remain constant?

    <p>When saturation point happens, where there is a high substrate concentration.</p> Signup and view all the answers

    When saturation is reached, the reaction rate is independent of what?

    <p>The reaction rate is independent of substrate concentration.</p> Signup and view all the answers

    In a graph of reaction rate vs substrate concentration, in which region is the enzyme saturated with substrate?

    <p>In the region where there is a high substrate concentration and the hyperbola begins to be a horizontal line.</p> Signup and view all the answers

    What is your best option for increasing the rate of the reaction when the enzyme is saturated?

    <p>Increase the enzyme concentration</p> Signup and view all the answers

    What are enzyme inhibitors?

    <p>Molecules other than substrates that bind to enzymes, slowing down the rate of the enzymatic reaction.</p> Signup and view all the answers

    What are the two classifications of enzyme inhibitors?

    <p>Irreversible and reversible.</p> Signup and view all the answers

    What are the two types of reversible enzyme inhibitors?

    <p>Competitive and non-competitive.</p> Signup and view all the answers

    What is a competitive inhibitor?

    <p>An inhibitor that has a structure similar to the substrate.</p> Signup and view all the answers

    What is a noncompetitive inhibitor?

    <p>An inhibitor that binds to a site on the enzyme that is not the active site.</p> Signup and view all the answers

    What does an irreversible inhibitor do?

    <p>Forms a covalent bond with an amino acid side group within the active site, preventing substrate binding.</p> Signup and view all the answers

    The competitive inhibitor competes with the substrate for the _____ on an enzyme.

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

    What happens to the enzyme's shape when a noncompetitive inhibitor is bonded?

    <p>The shape of the enzyme is distorted.</p> Signup and view all the answers

    Enzyme inhibitors disrupt normal interactions between an enzyme and its _____

    <p>Substrate.</p> Signup and view all the answers

    How can you decrease the effect of the competitive inhibitors?

    <p>They can be outcompeted by adding extra substrate.</p> Signup and view all the answers

    What do noncompetitive inhibitors do?

    <p>Inhibit the enzyme by binding elsewhere and changing its shape.</p> Signup and view all the answers

    What do irreversible inhibitors do?

    <p>Bind directly to the active site, permanently altering the enzyme structure.</p> Signup and view all the answers

    What is an example of competitive inhibitors?

    <p>Medications like penicillin and aspirin.</p> Signup and view all the answers

    You have an enzymatic reaction at the optimum pH and temperature. You add a competitive inhibitor and notice the reaction slows down. What can you do to speed the reaction up again?

    <p>Add more substrate; it will outcompete the inhibitor and increase the reaction rate.</p> Signup and view all the answers

    The phosphorylation of glucose to generate glucose-6-phosphate is catalyzed by hexokinase. This enzyme is allosterically inhibited by its own product, glucose-6-phosphate. This is an example of _____

    <p>Feedback regulation.</p> Signup and view all the answers

    Feedback inhibition is also known as _____

    <p>End-product inhibition.</p> Signup and view all the answers

    Which of the following best describes a metastable state?

    <p>The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst.</p> Signup and view all the answers

    What is the site on an enzyme that will bind the substrate called?

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

    Which of the following is an enzyme?

    <p>Carboxypeptidase A</p> Signup and view all the answers

    The EC system for naming enzymes is based on which of the following criteria?

    <p>The six major classes of enzyme function</p> Signup and view all the answers

    What may substrate activation involve?

    <p>Donation of protons to the enzyme, a change in enzyme conformation induced by substrate binding, formation of temporary covalent bonds, accepting protons from the enzyme.</p> Signup and view all the answers

    The induced-fit model involves what?

    <p>A conformational change in the shape of the enzyme.</p> Signup and view all the answers

    Which of the following is not a means of enzyme regulation?

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

    Covalent modification affects the activity of an enzyme by _____

    <p>All of the above</p> Signup and view all the answers

    Study Notes

    Enzymes as Biological Catalysts

    • Enzymes are primarily proteins that act as organic catalysts to accelerate biochemical reactions without being consumed.
    • They work by reducing the energy of activation (EA), allowing reactions to proceed more easily.

    Substrates and Active Sites

    • The reactants in enzymatically catalyzed reactions are called substrates.
    • The active site is the specific region of the enzyme where substrates bind through weak chemical interactions.

    Reaction Dynamics

    • Enzymes remain unchanged after reactions, meaning they can catalyze subsequent reactions.
    • Increasing substrate concentration typically enhances reaction rates until saturation occurs, at which point all active sites are occupied.

    Energy Considerations

    • Even spontaneous reactions (exergonic) require an initial energy input (energy of activation) to start.
    • A low reaction rate at temperatures below optimal levels often indicates insufficient energy for the reaction to proceed.

    Specificity of Enzymes

    • Enzymes exhibit high specificity due to their unique three-dimensional structures, allowing them to interact only with particular substrates.
    • Competitive inhibitors resemble substrates and bind to the active site, while non-competitive inhibitors attach elsewhere, altering the enzyme's shape.

    Inhibition Types

    • Irreversible inhibitors form covalent bonds with enzymes, permanently inactivating them.
    • Reversible inhibitors can be competitive or non-competitive, affecting enzyme activity without permanent changes.

    Regulation of Enzymatic Activity

    • Feedback inhibition occurs when a product of a metabolic pathway inhibits an enzyme involved in its own synthesis, maintaining metabolic balance.
    • Enzyme activity can be modulated by processes such as allosteric regulation and covalent modification (e.g., adding phosphate groups).

    Metastable States and Catalysis

    • The metastable state reflects a condition where substrate reactions can occur but typically require a catalyst to overcome energy barriers.
    • The induced-fit model illustrates how enzyme conformations change in response to substrate binding, enhancing catalytic efficiency.

    Enzyme Classification

    • Enzymes are categorized into six major classes based on their functions, according to the Enzyme Commission (EC) system.
    • Examples of enzymes include carboxypeptidase A, a well-characterized proteolytic enzyme.

    Practical Implications

    • Competitive inhibitors can be outcompeted by increasing substrate concentration.
    • Enzyme regulation is essential for cellular function, and understanding these mechanisms informs drug development and metabolic engineering.

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    Description

    Test your knowledge on enzymes and their functions with this flashcard quiz based on Chapter 6 of Biology. Discover how enzymes act as catalysts in biochemical reactions and learn about their properties and mechanisms. Perfect for preparing for your upcoming biology exam!

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