Biochemistry: Enzymes Lecture 9
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Questions and Answers

What is the role of enzymes in biological reactions?

  • They increase the energy barrier for reactions
  • They act as substrates
  • They lower the activation energy for reactions (correct)
  • They participate directly in the reaction
  • What is a holoenzyme?

  • An enzyme without its cofactors
  • A complete, functional enzyme with its cofactors (correct)
  • An enzyme with a damaged active site
  • A non-functional enzyme
  • Where does the substrate bind and catalysis occur in enzymes?

  • Inactive site
  • Active site (correct)
  • Inactive region
  • Catalytic site
  • What is the term for the energy barrier that substrates need to overcome before a reaction will occur?

    <p>Activation energy</p> Signup and view all the answers

    What happens to the activation energy required when enzymes are present?

    <p>It decreases</p> Signup and view all the answers

    Do enzymes participate directly in the reaction?

    <p>No, they do not</p> Signup and view all the answers

    Which type of enzymatic action describes the process of joining two or more substrate molecules together?

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

    What are small organic molecules that act as cofactors for enzymes called?

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

    Which type of enzymatic specificity refers to the enzyme acting on a particular steric or optical isomer?

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

    Which model of enzyme binding suggests that the active site of the enzyme is complementary in shape to the substrate, with no change in shape upon binding?

    <p>Lock-and-key model</p> Signup and view all the answers

    What family of enzymes assists in the breakdown of carbohydrates?

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

    What term is used for cofactors that are tightly bound to enzymes?

    <p>Prosthetic groups</p> Signup and view all the answers

    Which type of specificity refers to the enzyme acting on molecules with specific functional groups?

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

    What are the most common cofactors?

    <p>Coenzymes and metal ions</p> Signup and view all the answers

    Which enzyme is used to break protein down into peptides in the stomach?

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

    What term is used for enzymes that contain tightly bound metal ions?

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

    Study Notes

    Role of Enzymes

    • Enzymes act as catalysts in biological reactions, increasing the rate without being consumed.
    • They lower the activation energy required for reactions, facilitating metabolic processes.

    Holoenzyme

    • A holoenzyme is the complete, active form of an enzyme that includes its apoenzyme and necessary cofactors.

    Substrate Binding and Catalysis

    • The substrate binds to the enzyme at the active site, where catalysis occurs.
    • The active site is specifically shaped to accommodate the substrate.

    Activation Energy

    • The energy barrier that substrates must overcome for a reaction to proceed is known as activation energy.
    • Enzymes significantly reduce the activation energy needed for reactions.

    Enzyme Participation

    • Enzymes do not get consumed in reactions; they participate but are restored at the end.

    Enzymatic Action Types

    • Ligase action describes the enzymatic process of joining two or more substrate molecules together.

    Cofactors

    • Small organic molecules that assist enzymes are referred to as cofactors.

    Enzymatic Specificity

    • Stereospecificity refers to the enzyme's action on a particular steric or optical isomer.
    • Group specificity means the enzyme acts on molecules with specific functional groups.

    Enzyme Binding Model

    • The lock-and-key model describes enzyme binding, where the active site is complementary in shape to the substrate and does not change upon binding.

    Enzyme Families

    • Amylase is part of the enzyme family responsible for breaking down carbohydrates.

    Cofactor Terms

    • Tightly bound cofactors are termed prosthetic groups.

    Common Cofactors

    • The most common cofactors include vitamins and metal ions such as magnesium and zinc.

    Digestive Enzyme

    • Pepsin is the enzyme responsible for breaking proteins down into peptides in the stomach.

    Metal Ions in Enzymes

    • Enzymes containing tightly bound metal ions are called metalloenzymes.

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    Description

    Learn about enzymes, holoenzymes, substrates, and the catalytic role of enzymes in biological reactions. This lecture provides an introduction to the functions and structure of enzymes, presented by Dr. Michael Mounir from the Faculty of Science at Helwan University.

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