Introduction to Enzymes and Their History
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Questions and Answers

Which type of reaction is catalyzed by oxidoreductases?

  • Group transfer
  • Isomerization
  • Hydrolysis
  • Oxidation-reduction (correct)
  • What is the primary function of transferases?

  • Catalyzing oxidation-reduction reactions
  • Transferring functional groups between molecules (correct)
  • Rearranging atoms within a molecule
  • Catalyzing hydrolysis reactions
  • Which enzyme is classified as a hydrolase?

  • Lactate dehydrogenase
  • Amylase (correct)
  • Hexokinase
  • Transaminase
  • What type of bond does a hydrolase act upon?

    <p>Various bonds by adding water (D)</p> Signup and view all the answers

    Hexokinase catalyzes the transfer of a phosphate group from ATP to glucose, producing glucose-6-phosphate and ADP. To what class of enzymes does hexokinase belong?

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

    Which of the following enzymes is involved in oxidation-reduction reactions?

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

    Which of the following is an example of a transferase?

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

    What distinguishes hydrolases from other enzyme classes?

    <p>They catalyze reactions by adding water across a bond. (C)</p> Signup and view all the answers

    Which characteristic is NOT typically associated with enzymes?

    <p>They are consumed during the reaction they catalyze. (C)</p> Signup and view all the answers

    What was a key early misconception regarding enzymes, before Buchner's experiment?

    <p>Enzymes were considered inseparable from living cells for activity. (D)</p> Signup and view all the answers

    Which scientist's work directly contradicted Louis Pasteur's initial view on fermentation?

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

    Which statement best describes the role of the active site in an enzyme?

    <p>It creates a favorable chemical environment for a specific reaction to occur. (B)</p> Signup and view all the answers

    Which amino acid contains a sulfur atom in its side chain?

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

    Which of the following amino acids has a hydroxyl-containing side chain?

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

    Which of the following contains an aromatic side chain?

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

    Which of the following amino acids contains a basic side chain at pH 7?

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

    Which of the following exemplifies the catalytic efficiency property of enzymes?

    <p>Carbonic anhydrase enhances the hydration of $CO_2$ by a factor of $10^7$. (D)</p> Signup and view all the answers

    Urease catalyzing the hydrolysis of urea into carbon dioxide and ammonia is an example of what kind of specificity?

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

    An enzyme that acts on molecules containing amino, methyl, or phosphate groups exhibits what type of specificity?

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

    Esterase, which cleaves ester bonds regardless of the molecular structure, is an example of which type of specificity?

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

    Fumarate hydratase acting on fumarate to produce malate demonstrates which type of specificity?

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

    Which of the following best describes the reaction conditions under which enzymes typically operate?

    <p>37 ℃, physiological pH, and ambient atmospheric pressure (D)</p> Signup and view all the answers

    What is the rate enhancement range that characterizes the catalytic efficiency of enzymes?

    <p>$10^{3}$ to $10^{17}$ (B)</p> Signup and view all the answers

    Which of the following is NOT considered a key property of enzymes?

    <p>Requirement for extreme reaction conditions (D)</p> Signup and view all the answers

    Flashcards

    Hexokinase

    An enzyme that converts glucose and ATP into glucose-6-phosphate and ADP.

    ATP

    A molecule that provides energy for cellular processes.

    Glucose-6-Phosphate

    The phosphorylated form of glucose, important for metabolism.

    Oxidoreductases

    Enzymes that catalyze oxidation-reduction reactions.

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    Transferases

    Enzymes that transfer functional groups between molecules.

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    Hydrolases

    Enzymes that catalyze the hydrolysis of bonds using water.

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    Phosphotransferase

    A type of transferase that transfers phosphate groups.

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    Deaminases

    Enzymes that remove amine groups from molecules.

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    Catalytic efficiency

    The measure of how fast an enzyme catalyzes a reaction, typically much faster than uncatalyzed reactions.

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    Specificity of enzymes

    The ability of an enzyme to interact with only one or a few specific substrates, catalyzing a unique reaction.

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    Mild reaction conditions

    Enzymes operate best at physiological temperatures, pH, and pressure, unlike many chemical reactions.

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    Absolute specificity

    A type of specificity where an enzyme catalyzes only one reaction and one substrate.

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    Relative specificity

    A general term for enzymes that can act on multiple substrates having certain common features.

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    Group specificity

    An enzyme type that will act on substrates with specific functional groups, like amino or phosphate groups.

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    Bond specificity

    Enzymes that act on certain types of chemical bonds irrespective of the rest of the molecule.

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    Stereospecificity

    Enzymes that act on a specific steric or optical isomer of a molecule.

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    Enzymes

    Proteins that act as biological catalysts to accelerate chemical reactions.

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    Active Site

    The specific region on an enzyme where substrate molecules bind and undergo a chemical reaction.

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    Amino Acids

    Building blocks of proteins, each with unique side chains that determine their properties.

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    Hydrophobic Amino Acids

    Amino acids with non-polar side chains that repel water, impacting protein structure.

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    Basic Amino Acids

    Amino acids with positively charged side chains at physiological pH, such as lysine and arginine.

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    Acidic Amino Acids

    Amino acids with negatively charged side chains at physiological pH, like aspartic acid.

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    Globular Proteins

    Proteins that have a spherical shape, which is crucial for their function as enzymes.

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    Ferments

    Historical term for enzymes, especially those studied in fermentation processes.

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    Study Notes

    Enzyme Introduction

    • Enzymes are proteins
    • They catalyze biochemical reactions
    • They have a globular shape
    • Enzymes are complex 3-D structures

    Historical Perspectives

    • Biochemistry history intertwined with enzyme research
    • Enzymes first recognized in animal food digestion, sugar fermentation, and yeast processes
    • Enzymes initially thought to be inseparable from living cells, like yeast.
    • Eduard Buchner discovered that yeast extracts could ferment sugar to alcohol (demonstrating the concept of non-living enzymes)
    • James Sumner and John Northrop later established that all enzymes are proteins and won the Nobel Prize.
    • Later, catalytic RNA, also known as ribozymes, were discovered in the 1980s.

    Enzyme Nomenclature

    • Enzyme names often end in "-ase"
    • Enzyme names often describe the enzyme's function (e.g., sucrase catalyzes sucrose hydrolysis)
    • Some enzyme names describe both substrate and function (e.g., alcohol dehydrogenase oxidizes ethanol)
    • Some enzymes use common names (e.g. pepsin, trypsin)

    Enzyme Classification

    • Enzymes classified into six classes by the International Union of Biochemists (IUB)
    • Classification based on reactions catalyzed.
    • Classes include:
      • Oxidoreductases
      • Transferases
      • Hydrolases
      • Lyases
      • Isomerases
      • Ligases
    • Each enzyme has a unique classification number (e.g., EC:(2.7.1.1) HEXOKINASE)

    Enzyme Properties

    • Catalytic Efficiency: Enzymes are highly efficient, significantly speeding up reactions compared to uncatalyzed reactions.
    • Specifity: Highly specific, interacting with particular substrates and catalyzing a single type of reaction
      • Absolute specificity: catalyze only one reaction
      • Relative specificity: includes Group (e.g, amino), Bond (e.g., type of bond), Stereospecificity (e.g., specific isomer)
    • Mild Reaction Conditions: Operate under mild conditions (e.g., 37°C, physiological pH).

    Enzyme Active Site

    • The shape and chemical environment of the active site determine catalytic function

    Enzyme Examples and Functions

    • Oxidoreductases: Involved in oxidation-reduction reactions (e.g., lactate dehydrogenase). Examples include oxidases, peroxidases, and dehydrogenases
    • Transferases: Transfer functional groups between molecules (e.g., transaminases, kinases).
    • Hydrolases: Hydrolyze various chemical bonds by adding water atoms across chemical bonds (e.g. amylases, phosphatases). This includes peptidases, carbohydrases (like amylase, maltase, lactase), lipid hydrolyzing enzymes, deaminases.
    • Lyases: Cleave various bonds by means that are not hydrolysis and oxidation. This includes fumarase, carbonic anhydrase.
    • Isomerases: Catalyze isomerization changes within a single molecule by isomerizations(e.g. L-to-D).
    • Lyases: Many other examples including aldehydes, alcohols, and other types of functional groups.
    • Ligases/Synthases: Join two molecules through covalent bonds, using energy from ATP (e.g. glutamine synthetase)
    • Synthases: Biosynthetic reactions that don't use energy from ATP

    Enzyme Purification

    • Preparation for further study.

    Additional Notes

    • Enzymes are essential for life, and their specific role and function are crucial in numerous biochemical processes.
    • Many enzymes are called synthetases; however, some enzymes that catalyze biosynthetic reactions belong to classes other than ligases, called synthases.

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    Description

    This quiz covers the fundamental aspects of enzymes, including their structure, function, and historical significance in biochemistry. It highlights the discovery of enzymes and key figures in the field, such as Eduard Buchner and Nobel laureates James Sumner and John Northrop. Additionally, it explores the nomenclature of enzymes based on their activity and substrate interactions.

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