Enzymes Overview Quiz
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Questions and Answers

What is an enzyme?

An organic compound that acts as a catalyst for a biochemical reaction and increases the rate of reaction without being changed in the process.

Which of the following is NOT a feature of enzymes?

  • They can be changed in the process. (correct)
  • They are water-soluble.
  • They are very specific.
  • They enhance reaction rates.
  • What is a metalloenzyme?

    An enzyme that is bound tightly to a metal ion and does not dissociate even after extensive purification.

    An apoenzyme is the inactive form of an enzyme that requires a cofactor to become active.

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

    What is the reactant in an enzyme-catalyzed reaction called?

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

    Which of the following suffixes typically identifies an enzyme?

    <p>-ase (A)</p> Signup and view all the answers

    What type of reaction does a hydrolase enzyme catalyze?

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

    What type of enzyme catalyzes the transfer of a functional group from one molecule to another?

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

    Which of the following is NOT a subclass of transferases?

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

    Flashcards

    Enzyme

    An organic compound that acts as a catalyst in biochemical reactions, increasing the reaction rate without being consumed or altered.

    Coenzyme

    A small organic molecule that acts as a cofactor to assist an enzyme in its catalytic function.

    Cofactor

    A nonprotein component needed by certain enzymes for function. Can be an inorganic ion or organic molecule.

    Apoenzyme

    The protein part of a conjugated enzyme; inactive until combined with a cofactor.

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    Holoenzyme

    The complete, biologically active form of a conjugated enzyme (apoenzyme + cofactor).

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    Proenzyme (Zymogen)

    An inactive enzyme precursor that requires modification to become active.

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    Active Site

    The specific region on an enzyme where the substrate binds and the reaction occurs.

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    Substrate

    The reactant molecule upon which an enzyme acts.

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    Catalysis

    Increasing reaction rate by lowering activation energy.

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    Specificity

    Enzymes' ability to catalyze only specific reactions or bind only specific reactants.

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    Hydrolase

    Enzyme catalyzing hydrolysis reactions where water is used to break bonds.

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    Oxidoreductase

    Enzymes catalyzing oxidation-reduction reactions, often using coenzymes.

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    Transferase

    Enzyme catalyzing the transfer of a functional group from one molecule to another.

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    Lyase

    Enzyme catalyzing the addition or removal of groups from double bonds without hydrolysis or oxidation.

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    Isomerase

    Enzyme catalyzing the rearrangement of atoms within a molecule, creating isomers.

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    Ligase

    Enzyme catalyzing the joining of two molecules using energy from ATP.

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    Enzyme Classes

    Enzymes are grouped into classes based on the type of reaction they catalyze.

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    Enzyme Activity Regulation

    The process of controlling the rate of enzyme-catalyzed reactions to meet the cell's needs.

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    Enzyme Location

    The specific positions of enzymes in a cell, often crucial to their function.

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    Study Notes

    Enzymes

    • Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process.
    • They are typically proteins, but some RNA molecules can also act as enzymes, known as ribozymes.
    • Enzymes bind to specific molecules called substrates, facilitating their conversion into products.
    • The rate of an enzyme-catalyzed reaction is higher than the rate of the uncatalyzed reaction.

    Enzyme Features

    • Enzymes are highly specific, typically catalyzing only one or a small number of reactions.
    • Enzymes are subject to regulation, allowing cells to control their metabolic processes.
    • Enzymes are affected by temperature and pH, having optimal conditions for activity.
    • Enzymes do not change the equilibrium constant of a reaction.
    • Enzymes are reusable, participating in multiple rounds of catalysis.

    Metalloenzymes

    • Metalloenzymes are enzymes that require a metal ion for their activity.
    • The metal ion acts as a cofactor, assisting in the catalytic process.
    • Examples of metalloenzymes include:
      • Cytochrome oxidase: contains copper and iron ions
      • Carbonic anhydrase: contains zinc ions

    Apoenzymes and Cofactors

    • Apoenzymes are the inactive form of an enzyme that requires a cofactor to become active.
    • Cofactors can be inorganic ions (like metal ions) or organic molecules (like vitamins).
    • Holoenzyme is the fully active enzyme containing both the apoenzyme and the cofactor.

    Substrate

    • The reactant in an enzyme-catalyzed reaction is called the substrate.
    • The substrate binds to the enzyme's active site, forming an enzyme-substrate complex.

    Enzyme Nomenclature

    • Many enzymes end with the suffix -ase.
    • Examples include:
      • Lactase: breaks down lactose
      • Protease: breaks down proteins

    Hydrolases

    • Hydrolases are enzymes that catalyze the hydrolysis of a chemical bond, usually by adding water.
    • They break down larger molecules into smaller ones.
    • Examples include:
      • Lipase: breaks down lipids
      • Amylase: breaks down carbohydrates

    Transferases

    • Transferases catalyze the transfer of a functional group (like a phosphate group) from one molecule to another.
    • Examples include:
      • Kinases: transfer a phosphate group
      • Glycosyltransferases: transfer a sugar molecule
      • Methyltransferases: transfer a methyl group
    • Dehydrogenases are a subclass of transferases that transfer hydrogen ions and electrons.

    Subclasses of Transferases

    • Phosphotransferases: transfer phosphate groups

    • Glycosyltransferases: transfer sugar molecules

    • Methyltransferases: transfer methyl groups

    • Dehydrogenases: transfer electrons and hydrogen ions

    • Acyltransferases: transfer acyl groups

    • Isomerases are NOT a subclass of transferases. They catalyze the rearrangement of atoms within a molecule, converting one isomer to another.

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    Test your knowledge on enzymes, their structures, and functions with this comprehensive quiz. Explore the features of enzymes, including their catalytic roles, optimal conditions, and classification. Perfect for biology students learning about biochemistry.

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