Enzymology and Enzyme Structure
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Questions and Answers

What is the primary role of enzymes in chemical reactions?

  • To increase the rate of chemical reactions (correct)
  • To change the reactants into different substances
  • To alter the products of the reaction
  • To permanently modify reactants

    • Which type of enzyme structure is formed when an apoenzyme combines with its cofactor?

  • Metalloenzyme
  • Substrate complex
  • Holoenzyme (correct)
  • Cofactor component

    • What is denaturation of an enzyme?

  • The breakdown of the enzyme into amino acids
  • The irreversible formation of new enzymes
  • The change of an enzyme's substrate
  • The alteration of enzyme's structure affecting its activity (correct)

    • Which amino acid type is characterized as hydrophilic?

    <p>Aspartic acid</p> Signup and view all the answers

    What does the integrity of an enzyme's protein structure influence?

    <p>The catalytic activity of the enzyme</p> Signup and view all the answers

    What are cofactors in relation to enzymes?

    <p>An organic or inorganic molecule required for enzyme activity</p> Signup and view all the answers

    Which of the following factors does NOT affect the rate of enzymatic reactions?

    <p>Molecular weight of the enzyme</p> Signup and view all the answers

    What is the correct definition of an apoenzyme?

    <p>The protein part of an enzyme without its cofactor</p> Signup and view all the answers

    What is the primary entity transferred by Coenzyme A during reactions?

    <p>Acyl group</p> Signup and view all the answers

    Which coenzyme functions as a co-substrate in transamination reactions?

    <p>Pyridoxal phosphate</p> Signup and view all the answers

    What is the irreversible effect of dissociating biotin from its enzyme?

    <p>The enzyme loses its catalytic activity.</p> Signup and view all the answers

    Which of the following is NOT a correct pairing of a coenzyme and the entity it transfers?

    <p>Coenzyme B<sub>12</sub> - Carbon dioxide</p> Signup and view all the answers

    In the conversion involving succinate and FAD, what is the final product formed?

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

    What describes the role of a prosthetic group in enzymatic reactions?

    <p>It is permanently attached and crucial for activity.</p> Signup and view all the answers

    Which coenzyme is primarily involved in the transfer of hydrogen atoms?

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

    Which of the following reactions demonstrates the use of NAD+ as a coenzyme?

    <p>Glyceraldehyde 3-phosphate + Inorganic phosphate -&gt; 1,3-Bisphosphoglycerate</p> Signup and view all the answers

    What is the primary reaction catalyzed by pyruvate carboxylase?

    <p>Formation of oxaloacetate from pyruvate</p> Signup and view all the answers

    Which type of specificity allows an enzyme to act on a variety of substrates that share a functional group?

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

    Why are microbes preferred over plant and animal sources for enzyme production?

    <p>Microbes have a regular supply and lower production costs.</p> Signup and view all the answers

    Which of the following statements about the specificity of enzymes is correct?

    <p>Stereochemical specificity involves the enzyme acting on optical isomers.</p> Signup and view all the answers

    Which of the following is a potential disadvantage of using plant and animal enzymes compared to microbial enzymes?

    <p>Plant and animal enzymes can contain harmful materials.</p> Signup and view all the answers

    What is the primary function of an allosteric enzyme?

    <p>To alter enzyme activity based on effector molecules</p> Signup and view all the answers

    What are immobilized enzymes best known for?

    <p>Increasing enzyme stability and allowing for repeated use</p> Signup and view all the answers

    Which enzyme is paired correctly with its required metal cofactor?

    <p>Pyruvate kinase - K<sup>+</sup></p> Signup and view all the answers

    Which statement about metalloenzymes is true?

    <p>Metal ions are often essential for their enzymatic activity.</p> Signup and view all the answers

    What role do coenzymes typically play in enzymatic reactions?

    <p>They donate or accept chemical groups during the reaction.</p> Signup and view all the answers

    Isoenzymes are characterized by which of the following?

    <p>Variations in physical and biochemical properties while catalyzing the same reaction</p> Signup and view all the answers

    Which of the following statements regarding metal cofactors is incorrect?

    <p>All metalloenzymes require metal ions to function.</p> Signup and view all the answers

    What is the significance of effector molecules for allosteric enzymes?

    <p>They modulate enzyme activity by binding at locations other than the substrate-binding site.</p> Signup and view all the answers

    Study Notes

    Enzymology

    • Enzymology is the study of enzymes
    • Enzymes are proteins that act as catalysts, increasing the rate of chemical reactions.
    • Enzymes catalyze the binding of reactants (substrates), converting them to products, and releasing the products.
    • Enzymes return to their original form after the reaction.
    • Enzyme function depends on their protein structure integrity.
    • Factors that disrupt the native conformation of the enzyme's polypeptide chains can lead to loss of catalytic activity.

    Enzyme Structure

    • Enzymes are composed mainly of 20 naturally occurring amino acids.
    • Each amino acid conforms to the general formula: H₃N⁺-CH(R)-COO⁻ at a neutral pH.
    • Structural analysis of enzymes is done through methods of protein chemistry, molecular biology, and molecular biophysics.
    • There are specific classifications of amino acid chains based on their properties - Aliphatic, Hydrophilic, Sulfur-Containing, Aromatic, and Other. (figures showing structures are available in the provided images).

    Enzyme Denaturation

    • Denaturation is the partial or total alteration of an enzyme's structure, without changing its covalent structure.
    • Denaturation can be caused by physical procedures (heating, agitation) or chemical agents.
    • Denaturation can be reversible or irreversible.

    Structural Function Relationship

    • The catalytic activity of an enzyme relies on the integrity of its protein structure.
    • Factors disrupting the native conformation of the enzyme polypeptide chains lead to loss of catalytic activity.
    • Cofactor: A non-protein chemical component required for enzyme activity (e.g., metal ions, organic molecules called coenzymes).
    • Apoenzyme: The protein portion of an enzyme, without its cofactor.
    • Holoenzyme: The complete, active enzyme composed of apoenzyme + cofactor.
    • Examples of metal ions as cofactors for specific enzymes (metalloenzymes): Ca²⁺ (Lipase), Cu²⁺/Cu⁺ (Cytochrome oxidase, tyrosinase, etc.), Fe²⁺/Fe³⁺ (Cytochrome oxidase, etc.), K⁺ (Pyruvate kinase), Mg²⁺ (Hexokinase, etc.), Mn²⁺ (Arginase, etc.), Ni²⁺ (Urease), Zn²⁺ (Carbonic anhydrase, etc.)

    Coenzymes

    • Many coenzymes are derived from dietary water-soluble vitamins.
    • Coenzymes are involved in various biochemical reactions as either co-substrates or prosthetic groups.
    • Coenzymes function as donors or acceptors of chemical groups during biochemical reactions.
    • Examples include coenzyme A, Flavin adenine dinucleotide (FAD), and Nicotinamide adenine dinucleotide (NAD⁺). (structural formulas are included in the images)
    • Reactions involving NAD⁺ and FAD are presented in the provided images. These show how they are used in specific biochemical reactions.

    Co-substrates

    • Transient associates with the enzyme's active site.
    • Chemically modified during a reaction.
    • Released after the reaction is complete and free to participate in other reactions.
    • An example is pyridoxal phosphate in a transamination reaction. This acts as a temporary carrier for amino groups.

    Prosthetic Groups

    • Permanently bound to the enzyme's active site (either covalently or non-covalently).
    • Dissociation causes irreversible loss of catalytic activity.
    • An example is biotin, which is part of carboxylase enzymes.
    • Biotin is essential for the formation of oxaloacetate from pyruvate. (reaction shown in the provided images)

    Enzyme Specificity

    • Enzymes display varying degrees of specificity for their substrates.
    • There are four types of specificity:
      • Absolute specificity: catalyze only one reaction.
      • Group specificity: catalyze reactions involving a specific functional group.
      • Linkage specificity: catalyze reactions involving a certain chemical bond.
      • Stereochemical specificity: act on a particular steric or optical isomer.

    Sources of Enzymes

    • Enzymes occur in all living organisms.
    • Microbes are often preferred sources due to their relatively low cost of production, rapid growth in inexpensive media, and stability of the enzymes produced.
    • Plant and animal tissues may contain inhibitors or harmful compounds.

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    Enzymology Lecture Notes PDF

    Description

    This quiz explores the study of enzymes, their functions, and structural aspects. Understand how enzymes act as catalysts, the importance of their amino acid composition, and the factors affecting their activity. Test your knowledge on enzyme classifications and the chemistry behind their structures.

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